3 centres collaboration

Cervical shortening and cervical insufficiency

Table of contents

 

    Aim

    This guideline aims to offer advice to care providers on the assessment and management of women with a diagnosis of cervical shortening and/or cervical insufficiency.

    While preterm birth may be the final outcome for a woman with a shortened cervix, management of preterm birth per se is not the focus of this guideline. 3Centres has developed another guideline addressing preterm labour and birth (See Preterm Labour)

    Search and appraisal

    The following methods of search and appraisal were used: An Ovid platform database selection was made using Medline, Embase, Cochrane databases, for evidence published in English from the year 2000 onwards.

    Professional body websites were also used: American College of Obstetricians and Gynecologists (ACOG), Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG), Royal College of Obstetricians and Gynaecologists (RCOG), Society of Obstetricians and Gynaecologists of Canada (SOGC).

    Other websites accessed: National Health and Medical Research Council (NHMRC), National Institute for Health and Clinical Excellence (NICE) and BMJ Best practice.

    Where international guideline groups have cited levels of evidence, these have been referred to in the summary boxes at the conclusion of each section. Also see Appendix 4. Evidence tables.

    Search terms used were:  cervical insufficiency, cervical shortening, threatened preterm labour, cervical incompetence, cerclage, tocolytic(s), preterm birth, progesterone, progestational, cervical length

    In the compilation of these recommendations, international guidelines and the results of systematic reviews were used to compare facets of care. Contemporary reviews and recommendations from professional bodies were also used. Individual randomized controlled trials were used if they provided a high level of evidence, as determined by the NHMRC evidence level grading criteria.1

    In addition, a survey was circulated to the Women’s Hospitals Australasia (WHA) members to ascertain the routine practice among leading hospital clinicians for the care and management of women with cervical shortening. Seventy surveys were distributed and eleven replies were received, representing a 15.7% response rate. (Appendix 3)

    Following an iterative consultation process among key stakeholders from the three tertiary centres, a consensus of opinion was gained in most instances.  In cases of conflicting points of view, a variance process was initiated whereby the Co-Chairs of the 3centres Collaboration made the final decision.

    Introduction

    One of the challenges facing health care providers is the diagnosis and subsequent management of a woman with a shortened cervix.

    While there are many publications relating to the diagnosis and management of women with a shortened cervix, there is a paucity of high level evidence, such as randomised control trials, to support and guide clinical practice. In particular, there are several concerns with the current evidence that contribute to uncertainty about best management strategies. These include:

    • There is no uniform definition of a short cervix and cervical length varies with gestation.
    • Women are often not stratified into high risk or low risk/no previous risk factors.
    • While there is an association between a shortened cervix and preterm labour and birth, most women with a short cervix do not experience a preterm birth and most preterm births are not related to a cervical problem.

    It is hoped that this guideline will assist clinicians in the care of women who have been identified as having a short cervix, whether or not they have a prior history of preterm birth or pregnancy loss, thus reducing variation in clinical practice and improving pregnancy outcomes.

    It is further anticipated that the guideline will highlight the considerable uncertainties that remain in the provision of care for women with a short cervix. 

    The 3centres Collaboration encourages further research to better understand cervical shortening and predict pregnancy outcomes, with a view to developing improved aetiology-directed interventions.

    Cervical length measurement

    Measurement of cervical length by transvaginal ultrasound (TVU) is considered safe in pregnancy and has been shown to be well tolerated by women.2

    The Australian Society of Ultrasound in Medicine (ASUM) recommends that all women having a mid-trimester ultrasound scan should have their cervical length measured.3  ASUM does not provide the evidence to support this recommendation. Indeed, there is no evidence that routine cervical length measurement in all women improves pregnancy outcomes.4 Nonetheless, clinicians should be aware that as cervical lengths are increasingly being reported, it is more likely that they will be required to interpret cervical length measurements.

    Cervical length changes throughout pregnancy, progressively shortening towards term. Thus, average cervical length is dependant upon the gestation at which it is measured.

    Over the past decade or so there have been numerous studies reporting cervical length at varying gestations, in differing populations. The majority of published data relate cervical length at 22-25 weeks gestation. At this gestation, the median (50th centile) cervical length in singleton pregnancies equates to approximately 35mm.5 Other threshold values for clinical decision making at 24 weeks gestation correspond to: 30mm = 25th centile, 25mm = 10th centile, 20mm = 5th centile.

    In Australia the majority of women have their mid-trimester ultrasound examination performed at 18-20 weeks gestation. There are no published population data on cervical length at this gestation.

    Cervical length is most accurately measured by transvaginal ultrasound and only after the woman has emptied her bladder. The cervix is measured with the ultrasound probe directed into the anterior fornix of the vagina. Pressure on the cervix may artificially increase the length and should be avoided. The cervix is measured in the saggital view from the internal os to the external os. The measurement may be taken in a straight line or a curved line. The cervix should be assessed over several minutes and the shortest measurement reported.6 Cervical length measured in this manner is highly reproducible.

    In addition to measuring length, some authors have described the use of provocation tests to induce funnelling, such as fundal pressure, coughing, standing or Valsalva manoeuvre during assessment of the cervical length. There is no evidence that such tests improve the utility of cervical length as a predictor of pregnancy outcome when compared to cervical measurement without provocation.  In the absence of such evidence, cervical provocation tests cannot be recommended for clinical practice.7

    A variety of terms have been used to describe the cervix further, such as “funnelling”, “beaking” or “wedging”. These terms have been used with no clear definition, or distinction between them when during ultrasound, there is the invagination of the membranes and amniotic fluid into the proximal end of the endocervical canal. This invagination will continue as the cervix shortens and dilates. If the membranes remain intact there may be a large portion ballooning out into the vagina, known as “hourglass membranes”. The presence of funnelling with a shortened cervix is considered an ominous sign, associated with an increased risk of preterm birth.8

    Cervical length

    Definitions

    Short cervix

    Recognising the association between cervical shortening and risk of spontaneous preterm birth, the discovery of a short cervix may change the care offered to an individual woman.

    However, there are no uniform criteria defining a “short cervix”, and the inverse relationship between cervical length and risk of preterm birth is likely to be a continuum. The most frequently used definition of a shortened cervix is one that measures less than 25mm (10th centile) on a TVU scan at 20–24 weeks gestation. By definition, approximately 8-10% of women will have a cervical length of <25mm at 23 weeks gestation.9

    There is no evidence that targeting interventions by a cervical length of <25mm is associated with improved pregnancy outcomes. However, there is recent evidence that using a cervical length of <20mm (5th centile) in both population groups of women (no previous risk factors with a short cervix and those at high-risk of a preterm birth with a short cervix) may allow directed care that improves pregnancy outcomes.10

    For this reason 3Centres recommend using a cervical length ≤20mm at 18-22 weeks gestation to define a threshold where specific care may then be considered.

    In addition to cervical length per se, clinicians are encouraged to consider other factors that may put the woman at high risk for spontaneous preterm birth such as the number of fetuses, the presence of infection, previous obstetric history, the presence or absence of symptoms, rate of change of cervical length and gestational age at which the cervical length was obtained. (The earlier in gestation the shortening is detected, the higher the risk of preterm birth)

    Cervical insufficiency

    Cervical insufficiency is thought to be due to a congenital or acquired (e.g. by previous surgery) structural weakness of the cervix.

    The term “cervical incompetence” is considered pejorative and insensitive. It is recommended that this term is no longer used.

    Typically, women with cervical insufficiency present with painless, cervical shortening and dilatation in mid-pregnancy, which is sometimes associated with an increased, watery vaginal discharge, and/or increasing pressure symptoms.

    Cervical insufficiency is associated with an increased risk of mid-trimester pregnancy loss or preterm birth and this guideline also aims to direct future care for those women with a past diagnosis of cervical insufficiency that has led to a pregnancy loss.

     Definition

    Cervical length and risk of preterm birth

    There is a strong inverse relationship between cervical length in mid-pregnancy and the risk of preterm birth. Measurement of cervical length provides an accurate prediction of that risk. This relationship is particularly enhanced in women at high risk of preterm birth, such as those with a previous pregnancy loss or cervical surgery. In essence, the shorter the cervix, the earlier the gestation, the higher the risk of preterm birth, a risk that is exacerbated if other risk factors are present.5

    For example, in a large (nearly 40,000 women) population-based prospective multicentre study:
    1% of women had a cervix <15mm and 35% of these women gave birth before 32 weeks; 20% of women had a cervix 16-25mm and 10% of the women gave birth before 32 weeks.11 

    Similarly, in another large study, 2% of women had a cervical length ≤ 15 mm at 23 weeks; these women accounted for 90% and 60% of the women experiencing a preterm birth at ≤ 28 and ≤ 32 weeks, respectively.9

    If a shortened cervix is observed on ultrasound scan at 18-22 weeks gestation, women should be able to have an extensive discussion about the risks of preterm birth with a senior obstetrician and/or a neonatologist. Written information should also be provided.

    Short cervix in a general, low-risk population

    In a low-risk population without recognised risk factors, the incidence of preterm birth before 35 weeks gestation when cervical length was <25mm measured at 24 weeks gestation, has been reported in one paper as 3% in a population of 2107 women studied.12

    Short cervix in a high-risk population

    In addition to cervical length, an individual woman’s medical and pregnancy history and ethnic origin may also identify her at high risk of spontaneous preterm birth. 

    The following table, derived from a population of high-risk women, is a further illustration of the predictive value of cervical length and the risk of preterm birth. It may be useful when discussing on-going management options with women. 

     Table 1. Predicted probability of preterm delivery before week 28, by cervical length (mm) and time of measurement (week of pregnancy) in a high-risk population. Adapted from: Berghella et al 2007.13

    Table 1

    Cx length preterm

    Management options - General

    Conservative management

    In the absence of specific evidence, in certain circumstances clinicians in consultation with the woman, may reasonably choose conservative management as the initial preferred option. See population specific options.

    Cervical surveillance

    As above and due to the heterogeneity of many research studies, cervical surveillance by transvaginal ultrasound serial scans, may be the option of choice. See population specific options.

    Progesterone

    In recent years there has been renewed interest in the use of prophylactic progesterone in women at high-risk of preterm birth. A number of randomized clinical trials have been completed that address different populations of women however, the optimal dose, route of administration, and gestational age at which to commence and cease progesterone therapy, remains inconclusive at present. A number of other clinical trials are on-going that may assist in informing future practice. See population specific options for 3centres recommendations.

    Cervical cerclage

    There have been various terms used to describe cervical cerclage sutures such as prophylactic, therapeutic or emergency. These terms are now considered ambiguous and therefore for the purpose of this guideline, we have used the definitions of cervical sutures as suggested by the Royal college of Obstetricians and Gynaecologists in May 2011 as follows:14

    History-indicated cerclage
    Insertion of a cerclage as a result of factors in a woman’s obstetric or gynaecological history, which increases the risk of spontaneous second-trimester loss or preterm delivery. A history-indicated suture is performed as a prophylactic measure in an asymptomatic woman and normally inserted electively at 12–14 weeks of gestation.

    Ultrasound-indicated cerclage
    Insertion of a cerclage as a therapeutic measure in cases of cervical length shortening seen on transvaginal ultrasound. Ultrasound-indicated cerclage is performed on asymptomatic women who do not have exposed fetal membranes in the vagina. Sonographic assessment of the cervix is usually performed between 14 and 24 weeks of gestation.

    Rescue cerclage
    Insertion of cerclage as a salvage measure in the case of premature cervical dilatation with exposed fetal membranes in the vagina. This may be discovered by ultrasound examination of the cervix or as a result of a speculum/physical examination performed for symptoms such as vaginal discharge, bleeding or ‘sensation of pressure’. 

    The decision to place a rescue cerclage should be individualised and is dependant upon the gestation at presentation. 3centres recommends caution when considering inserting a rescue cerclage at later gestations as there is insufficient evidence to recommend this practice. A senior obstetrician should be involved in this decision making.

    Cerclage type
    There are two types of transvaginal cerclage, Shirodkar and McDonald. The Shirodkar technique involves reflecting vaginal skin allowing placement of the suture high up around the cervix, as close as possible to the level of the internal cervical os. The McDonald ‘purse string’ technique involves inserting the suture around the intravaginal portion of the cervix, without reflection of vaginal skin, and is technically simpler to perform. Currently, there is no evidence to recommend one type of suture over the other.

    Transabdominal cerclage, either by laparoscopy or laparotomy, is an option if a previous transvaginal cervical cerclage has failed or it is not technically possible. Laparoscopic placement of a cerclage can be performed in pre-pregnancy or in early pregnancy. Both transabdominal cerclage options require a general anaesthetic. The fetus is later delivered by caesarean section. 

    Clinicians should decide which technique to use, based on their experience and expertise, and on the woman’s history.

    Cervical cerclage may be placed under a regional or general anaesthetic.

    Cerclage complications
    Recognised complications of cervical cerclage include bleeding from suture placement, infection, preterm prelabour rupture of membranes (PPROM). Suture displacement secondary to uterine contractions may also occur, owing to the presence of a foreign body. Also, with the use of a general anaesthetic for any procedure, there are potential anaesthetic risks to consider.

    There is insufficient evidence to guide practice when a woman has preterm pre-labour rupture of membranes (PPROM) and a cervical cerclage in situ. The results from an on-going multi-centre trial will help to guide future practice.15 Until the results from that trial have been published, most common clinical practice is to remove a cervical suture if a woman presents with PPROM.

    Transvaginal cerclage should be removed in late pregnancy to allow a normal vaginal birth. There is limited evidence to guide the timing of removal but it is most common to remove a suture at or after 37 weeks gestation. Women should be counselled that there is about a 10% chance of spontaneous labour in the 48 hours following cerclage removal. Routine induction of labour at the time of cerclage removal cannot be recommended. The suture should be removed at any gestation in the presence of established labour or chorioamnionitis.15

    The role of perioperative antibiotics associated with cerclage placement.
    The use of unnecessary antibiotics may lead to the development of resistant strains of bacteria.
    This has implications for other morbidity for the woman and her fetus. Therefore, the use of prophylactic antibiotic therapy is not recommended.

    The role of Indomethecin/tocolytics following cerclage placement
    In two studies, the use of indomethecin following ultrasound indicated placement of cerclage, did not demonstrate a reduction in preterm birth when compared to those receiving cerclage alone. The routine use of Indomethecin is not recommended until future research can guide practice.16,17 There have been no randomized studies to show that the routine use of any tocolytic therapy after cerclage placement is effective. Therefore, routine tocolytic therapy following cerlage placement cannot be recommended.

    Rest

    Hospitalisation and bed-rest have been the past recommendations by many clinicians. However, there is no evidence that bedrest improves pregnancy outcomes in women who have a finding of a short cervix. Bed rest and/or hospitalization is not recommended for any population group unless very individual circumstances dictate it so.18,19

    Population specific management options

    General population - Low-risk women

    It is important to be able to advise and provide appropriate care for low-risk women who have no previously known risk factors and have an incidental finding of a shortened cervix on a routine TVU scan. The number of these women may be increasing due to the widespread use of high quality ultrasound and use of the transvaginal route.

    Conservative management:

    There is insufficient evidence to recommend routine transvaginal serial ultrasound assessment of cervical length in women with no risk factors. Ultrasound screening lacks the discriminatory power to be used effectively in a low risk population. However, in the case of a routine ultrasound study of the fetal and maternal anatomy, cervical length may often be included in the assessment.

    In women with a cervical length of between 20-25mm, there is insufficient evidence to support any specific intervention. These women should be advised that their risk of spontaneous preterm birth is less than 5%. In the absence of evidence, some clinicians may choose to repeat TVU length measurement 1-2 weeks later.

    If an incidental finding of a shortened cervix is diagnosed but has not reached ≤ 20mm, there is limited evidence available to recommend any other form of management beyond additional surveillance. In this situation, an experienced clinician should review the ultrasound findings and discuss options with the woman, according to her physical and psychosocial circumstances. Routine admission to hospital cannot be recommended, as there is no evidence that hospitalisation or bed-rest reduces the risk of preterm birth in these women.

    Progesterone:

    There is limited evidence examining the effectiveness of vaginal progesterone solely in a low-risk population of women with an incidental finding of a short cervix.

    In one trial that included low and high-risk women, the authors concluded that in women whose cervix was <15mm, by giving 200mg of vaginal progesterone daily from 24 – 34 weeks gestation, their risk of preterm birth reduced by 44% (19% in the placebo group, 34% in the progesterone group). This was not associated with a significant improvement in neonatal outcome.20

    A multicentre, randomised, double-blind, placebo controlled trial, in a mixed population (risk stratified-16% had a history of preterm birth), 458 women with a shortened cervix (10-20 mm) at 19 - 24 weeks gestation, were administered 90mg of vaginal progesterone gel. In women without a history of preterm birth (84% of the population), vaginal progesterone administration was associated with a significant reduction (almost 50%) in the rate of preterm birth before 33 weeks, (7.6% vs 15.3%).

    Within the whole treatment group, overall there was a 45% reduction in the rate of preterm birth before 33 weeks gestation, and improved neonatal outcomes.10

    3 centres Collaboration recommends offering vaginal progesterone 90mg - 200mg to women who are shown to have a cervix <20mm at 18-22 weeks gestation. On average, this would be expected to halve their risk of preterm birth.

    Alternatively, the offer of vaginal progesterone (200mg capsule nocte) is recommended to women who are shown to have a cervix <15mm at 20-25 weeks gestation. On average, this would expect to reduce their risk of preterm birth at <34 weeks by 44% 

    Cervical cerclage:

    There is no evidence to show that the insertion of an ultrasound indicated cerclage in women in whom the diagnosis of a short cervix is an incidental finding, improves pregnancy outcome. Accordingly, cervical cerclage is not recommended for women who have an incidental finding of a short cervix.21

    Rest:

     There is no evidence that bedrest improves pregnancy outcomes in women who have the incidental finding of a short cervix. Bed rest and/or hospitalization is not recommended.18,19,22

    High-risk women - Asymptomatic

    Women at high-risk of preterm birth are those where there is often a history of multiple cervical dilatations,23other cervical trauma, surgical intervention such as a cone biopsy or obstetric trauma, uterine malformations, multiple pregnancy, ethnicity, low BMI or most commonly, previous pregnancy loss in the second or early third trimester, where there is no fetal cause for the pregnancy loss.24
     

    The risk factors for cervical shortening leading to preterm birth should be evaluated at the first antenatal visit. Because cervical shortening may lead to preterm birth, the risks of preterm birth should be discussed with all high-risk women. The outcome of all discussions needs to be clearly documented.

    There is insufficient evidence on which to base strong recommendations for the management of women at high risk of cervical shortening and preterm birth. In discussion with the woman, clinicians may choose from three broad approaches to management, singularly or in combination. Care for each woman is individualised, dependent upon her gestation, history and circumstances, and on the considerations of an experienced clinician. 

    Cervical surveillance:

    If cervical length surveillance is the preferred management option for high-risk women, then serial TVU scans should be offered, starting at about 16 weeks gestation, or earlier if indicated by the woman’s history and risk factors.25 It may also be appropriate that the frequency of antenatal visits is increased to allow timely review of the ultrasound results.

    There is no agreed optimum frequency of cervical scanning. In general, it is recommended that cervical ultrasounds should be performed from weekly to every four weeks. However, the frequency of ultrasound scanning is dictated by the gestation, cervical length, and rate of change, pre-existing risk factors or if there is a change in the clinical picture. A woman with changing symptomatology, increasing pelvic pressure or mucoid discharge, may require more frequent scans. The benefit of cervical surveillance is that it is a non-invasive option.

    If changes are observed on ultrasound surveillance then the next step(s) in management should be discussed with the woman.

    Progesterone:

    Systematic reviews from a number of randomised trials have shown that progesterone reduces the risk of preterm birth in high-risk women, who have had a previous, spontaneous preterm birth.26,27

    In the population of women at high risk for preterm birth who currently have a normal cervical length, two trials of significance demonstrated that the use of prophylactic progesterone reduced their incidence of preterm labour and birth. 

    In the first trial, a daily dose of 100mg of vaginal progesterone in women with a history of preterm birth, administered between 24–34 weeks gestation, showed that progesterone administration was associated with delayed cervical shortening as pregnancy progressed, a lower rate of preterm birth, a lower frequency of newborn admission to the intensive care unit and a shorter length of neonatal stay.28

    More recently, a secondary analysis of one randomized controlled trial suggested that the use of progesterone is more effective in prolonging pregnancy of women with a history of spontaneous preterm birth <34 weeks gestation. Women were given progesterone (17-alpha hydroxyprogesterone caproate) from 15-20+4 weeks gestation until 36 weeks gestation.29  17-alpha hydroxyprogesterone caproate is not currently available for use in Australia.

    If it is decided that vaginal progesterone is indicated, then until further evidence is available to guide otherwise, 3Centres recommends the use of 90-200mg vaginal progesterone suppository daily until 34 weeks gestation.

    Cervical cerclage:

    Recent data suggest that using ultrasound to identify women at risk of cervical insufficiency because of a history of preterm birth reduces unnecessary cerclage rates and results in similar pregnancy outcomes as cerclage placement on the basis of history alone.30,31 Thus, the use of cervical surveillance for identifying cerclage candidates may usefully reduce the number of cerclages inserted.

    A history indicated cerclage is inserted in asymptomatic women who are at risk of mid-pregnancy loss and/or very preterm birth based on previous obstetric risk factors (>2 previous PTB) where the attending clinician(s) believe that cervical insufficiency was a major contributor to the loss.14

    The suture is placed prior to any cervical change, typically at 13-16 weeks gestation, once the risk of early miscarriage has passed. Insertion at 14 weeks also allows completion of first trimester aneuploidy testing, if desired, prior to cervical cerclage. 

    Rest:

    Clinicians often recommend additional rest in the belief that it reduces the gravitational challenge on the cervix, particularly where physical exertion (prolonged standing, long occupational hours, heavy lifting etc) may increase the likelihood of preterm birth. However there is no direct evidence that recommending bed-rest is beneficial for a woman at risk of preterm labour and it should not be recommended.18,19

    High-risk women with a short cervix

    This group of high-risk women are found to have a shortened cervix during surveillance.

    The management options to be considered and discussed with an individual woman who has been shown to have a shortened cervix will depend on the clinical situation, including other signs or symptoms of labour or chorioamnionitis, the number of fetuses in utero, other high-risk factors, cervical length and gestational age at which the cervical length was obtained. The management options detailed in this guideline relate to the woman with a singleton pregnancy who is not in labour and who does not have chorioamnionitis.

    Cervical surveillance:

    As per cervical surveillance option above for high-risk women - asymptomatic. However, without some form of intervention, the risk of fetal loss is high in this group of women and therefore it is not likely to be the preferred option.

    Progesterone:

    In addition to the use of progesterone in a mixed population of high and low risk women, there are two more trials that focused on those high-risk women who presented with a shortened cervix.

    The first in 2007 De Franco et al, (as a secondary analysis of the O’Brien et al trial in 2007), concluded that women at high-risk for a preterm birth who had a short cervix, should be offered progesterone 90mg daily if their cervix measured <28mm.32

    The O’Brien et al trial in 2009 reported that by offering high-risk women whose cervix was <25mm 90mg of progesterone daily, this will significantly preserve the cervical length.33

    The optimum dose and timing of progesterone remains to be determined. Until further evidence is available to better guide practice, 3Centres recommends the use of 90mg-200mg progesterone daily, or 200mg nocte until 36 weeks gestation.

    Cervical cerclage:

    A trial of ultrasound indicated cerclage in women with a history of preterm loss between 17 and 37 weeks gestation and cervical length <25mm detected at 16-22 weeks gestation, concluded that cerclage prevented preterm birth when compared to expectant management at <24 weeks gestation 6.1% versus 14%; P = 0.03) and perinatal death (8.8% versus 16%; P = 0.046) but did not prevent birth at less than 35 weeks of gestation (32% versus 42%; OR = 0.67; 95% CI 0.42–1.07) unless cervical length was less than 15 mm (OR 0.23; 95% CI 0.08–0.66)34

    Further, the results from a meta analysis of four RCT’s reviewing cerclage, showed that the intervention seemed to have a similar effect regardless of the degree of cervical shortening, including cervical lengths of 16–24 mm, as well as cervical lengths of 15.9mm.35

    If cerclage is the preferred management option in a woman who has had one or more mid-trimester losses, 3centres recommend that it be placed at <25 weeks gestation and only if the cervix has reached ≤25mm.

    Rest:

    There is no direct evidence that recommending bed-rest is beneficial for a woman at risk of preterm labour and it should not be recommended.18,19

    Women with multiple gestation

    While women with a multiple pregnancy are considered high-risk for preterm labour and birth, there is insufficient evidence to support the recommendations for cervical cerclage as per the previous categories.18,20,36 

    Similarly, there is insufficient evidence to recommend the use of progesterone for women with multiple gestations.37,38

    Fetal fibronectin test (fFN)

    Occasionally a woman may present with a shortened cervix who is contracting. The treating clinician needs to ascertain whether this is an incidental finding of a shortened cervix or a short cervix that has effaced as part of preterm labour and if risk factors are present.

    A negative fFn test has a very high negative predictive value: 99% of women with a negative result will not proceed to give birth in the following 7 days.

    In one study in a high-risk pregnancy, the use of cervical length measurements in combination with fFN testing regardless of risk factors, concluded that a short cervix predicted a subsequent positive fetal fibronectin result, and a positive fetal fibronectin result predicted subsequent cervical shortening.39Therefore the use of fFN test in the presence of a short cervix might assist with further management.

    Factors that may affect the fFN test results: Any cervical manipulation within the previous 24 hours, such as coitus, digital vaginal examination and TVU examination may affect the result. However, this should not dissuade the clinician from performing the test, even in the face of a positive result due 

    to extraneous factors. Fetal fibronectin is also found in blood and semen, and these may cause false positive results however, negative results in any of these settings can still be considered reliable.

    Dependant upon her gestation, if the woman is not already in a level 6 (tertiary) care setting, is symptomatic with a positive fFN result, it is advisable that the clinician consult with the Perinatal Emergency Services (PERS) for further assistance. (See below- Location of care)

    Table 3. Fetal fibronectin test

    fFN

    Location of care

    The location of care will be dependent upon risk factors, gestation, planned management and the hospital facilities. At the extremes of gestation (less than 23 weeks and greater than 32-37 weeks), in consultation with specialists at a level 6 (tertiary) hospital, it may be suggested that the on-going management of women with a shortened cervix could be provided from a local secondary hospital.

    Women who present with a shortened cervix between 23-32 weeks gestation, may be managed in consultation with clinicians at a Level 6 (tertiary level) hospital.

    When management has been instituted and the woman is clinically stable, ongoing management as an outpatient can be considered.  If outpatient management is offered, women should be provided with clear follow-up arrangements and twenty-four hour access to obstetric services.  

    Location

    Post pregnancy loss

    All women who have had a second or third trimester pregnancy loss or preterm delivery due to cervical shortening should be offered a follow up postnatal consultation with a senior obstetrician. This would usually be organised for about six weeks postpartum. Discussion about the management of future pregnancies is important.

    Information regarding the pregnancy, cause of cervical shortening and delivery should be provided to the general practitioner, as well as a plan for future pregnancies.

    Equivocal evidence or unlikely to be of benefit for practice

    Equivocal

    Evidence is lacking and further research is required

    Lacking

    Footnotes

    1. NHMRC  Levels of evidence and grades for recommendations for developers of guidelines. December 2009. Available from: www.nhmrc.gov.au/_files_nhmrc/filehttp://3centres.com.au/guidelines/evidence_statement_form.pdf
    2. Dutta R, Ultrasound in Obstetrics & Gynecology: The official Journal Of The International Society Of Ultrasound in Obstetrics And Gynecology (Blackwell) Volume: 22 Issue 5 (2003-01_01) p.503-507. ISSN:0960_7692
    3. Australasian Society for Ultrasound in Medicine, polices and statements - guidelines for the mid trimester obstetric scan. Available from: http://www.asum.com.au/site/files/P&S/D2_policy.pdf
    4. Berghella V, Baxter JK, Hendrix NW. Cervical assessment by ultrasound for preventing preterm delivery. Cochrane Database of Systematic Reviews 2009, Issue 3. Art. No.: CD007235. DOI: 10.1002/14651858.CD007235.pub2.
    5. Iams JD, Goldenberg RL, Meis PJ, Mercer BM, Moawad A, Das A, Thom E, McNellis D, Copper RL, Johnson F, and Roberts JM. The length of the cervix and the risk of spontaneous premature delivery. The New England Journal Of Medicine, 334(9):567–572, 02 1996.
    6. Fetal Medicine Foundation. Available from: https://courses.fetalmedicine.com/fmf/introduction.
    7. RANZCOG. Measurement of cervical length in pregnancy for prediction of preterm birth. Available from: www.ranzcog.com.au
    8. Angtuaco TL et al, Expert Panel on Women's Imaging. ACR Appropriateness Criteria® assessment of gravid cervix. American College of Radiology (ACR); 2008. 5p
    9. Heath VC, Southall TR, Souka AP, et al: Cervical length at 23 weeks of gestation: prediction of spontaneous preterm delivery. Ultrasound Obstet Gynecol 12:312-317, 1998.
    10. Hassan S, et al, 2011;Vaginal progesterone reduces the rate of preterm birth in women with a sonographic short cervix: a multicenter, randomized, double-blind, placebo-controlled trial ;Ultrasound in Obstetrics & Gynecology (in press) DOI: 10.1002/uog.9017.
    11. To MS, Skentou CA, Royston P, et al: Prediction of patient-specific risk of early preterm delivery using maternal history and sonographic measurement of cervical length: a population-based prospective study. Ultrasound Obstet Gynecol 27:362-367, 2006.
    12. Iams JD, Goldenberg RL, Mercer BM, Moawad AH, Meis PJ, Das AF, Caritis SN, Miodovnik M, Menard MK, Thurnau GR, Dombrowski MP, and Roberts JH. The preterm prediction study: can low-risk women destined for spontaneous preterm birth be identified? American Journal Of Obstetrics And Gynecology, 184(4):652–655, 03 2001.
    13. Berghella V, Roman A, Daskalakis C, Ness A, and Baxter JK. Gestational age at cervical length measurement and incidence of preterm birth. Obstetrics And Gynecology, 110(2 Pt 1):311–317, 08 2007. 
    14. Shennan AH, To MS: RCOG Green Top Guidelines: Cervical cerclage RCOG. 2011. Available from: www.rcog.org.uk
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    Additional references

    • Berghella V. Novel developments on cervical length screening and progesterone for preventing preterm birth. BJOG 2009;116:182–187.
    • Berghella V Ultrasound assessment of the cervix Clin.Obstet Gynecol. 2003; 46: 947-62
    • BMJ-Best Practice. Prophylactic cervical cerclage in women at risk of preterm labour with protruding membranes. Available from: http://bestpractice.bmj.com/best-practice/evidence/intervention/1404/1/sr-1404-i15.html. Accessed December 2009.
    • Bisulli, M et al. Interval to spontaneous delivery after elective removal of cerclage. Am J Obstet Gynecol 201(2):163.e1-4 (2009)
    • BMJ-Best practice. Prophylactic cervical cerclage in women at risk of preterm labour with cervical changes. Available from: http://bestpractice.bmj.com/best-practice/welcome.html. Accessed December 2009.
    • BMJ-Best practice. Preterm birth available from:http://bestpractice.bmj.com/best-practice/evidence/1404.html. Accessed December 2009.
    • BMJ-Best Practice. Antibiotic treatment for preterm labour with intact membranes. Available from : http://bestpractice.bmj.com/best-practice/evidence/intervention /1404/0/sr-1404-i8.html. Accessed December 2009.
    • Cincotta R, Gardner D, Duncombe G, Flenady V. J.D. Antenatal administration of progesterone for preventing preterm birth (protocol). The Cochrane Database Syst Rev 2004. CD004947.
    • Daskalakis DJ, Prematurity prevention: the role of cerclage. Curr Opin Obstet Gynecol 21:148–152.
    • Hoesli I, M.Strutas D.; Tercanli S.; Holzgreve W. Charts for cervical length in singleton pregnancy International Journal of Gynecology and Obstetrics, Volume 82, Number 2, August 2003 , pp. 161-165(5).
    • Honest H, Bachmann LM, Coomarasamy A, Gupta JK, Kleijnen J, Khan KS. Accuracy of cervical transvaginal sonography in predicting preterm birth: a systematic review. Ultrasound Obstet Gynecol 2003; 22(3):305-22.
    • Jenkins SM Dynamic cervical change: is real-time sonographic cervical shortening predictive of preterm delivery in patients with symptoms of preterm labor? Ultrasound Obstet Gynecol 2006; 27: 373-6.
    • Odibo AO, Berghella V, To MS, Rust OA, Althuisius SM, Nicolaides KH. Shirodkar versus McDonald cerclage for the prevention of preterm birth in women with short cervical length. Am J Perinatol. 2007 Jan;24(1):55-60. Epub 2006 Dec 27.
    • Pramod R, Okun N, McKay D, Kiehn L, Hewson S, Ross S, Hannah ME. Cerclage for the short cervix demonstrated by transvaginal ultrasound: current practice and opinion. J Obstet Gynaecol Can. 2004. Jun;26(6):564-70.
    • RANZCOG College position statement. Measurement of cervical length in pregnancy for prediction of preterm birth. November 2008. Available from:www.ranzcog.edu.au/publications/collegestatements.shtml. Accessed November 2009.
    • Rode L, Langhoff-Roos J, Andersson C, Dinesen J, Hammerum M.S, Mohapeloa H , Tabor A. Systematic review of progesterone for the prevention of preterm birth in singleton pregnancies. Acta Obstetricia Et Gynecologica Scandinavica, 88(11):1180–1189, 2009.
    • Smith V; Devane D; Begley CM; Clarke M; Higgins S. A systematic review and quality assessment of systematic reviews of randomized trials of interventions for preventing and treating preterm birth. European Journal Of Obstetrics, Gynecology, And Reproductive Biology [Eur J Obstet Gynecol Reprod Biol] 2009 Jan; Vol. 142 (1), pp. 3-11.
    • Kenyon S, Boulvain M, Neilson J. Antibiotics for preterm rupture of membranes. The Cochrane Database Syst Rev 2003. CD001058.
    • King J, Flenady V, Cole S, Thorton S. Cyclo-oxygenase (COX) inhibitors for treating preterm labour. The Cochrane Database Syst Rev 2005. CD001992.
    • National Institute for Health and Clinical Excellence (NICE). Interventional procedure overview of laparoscopic cerclage for prevention of recurrent pregnancy loss due to cervical incompetence. August 2007. Available from: http://guidance.nice.org.uk/IPG228. Accessed November 2009.
    • SOGC. Ultrasound cervical assessment in predicting preterm birth. No. 102, May 2001.
    • Available: http://www.sogc.orghttp://3centres.com.au/guidelines/public/102E-CPG-May2001.pdf.
    • SOGC.  The use of progesterone for prevention of preterm birth. No. 202, January 2008, J Obstet Gynaecol Can 2008;30(1):67–71. Available: http://www.sogc.orghttp://3centres.com.au/guidelines/documents/guiJOGC202TU0801.pdf.

    Appendix 1. Short cervix management options - Flowchart

    Short cervix Flowchart (Opens in a new window)

    Appendix 2. Progesterone research summary

    Progesterone research summary (Opens in a new window)

    Appendix 3. WHA survey responses

    WHA survey page 1. (Opens in a new window)
    WHA survey page 2. (Opens in a new window)

    Appendix 4. Evidence tables

    NHMRC Evidence table (Opens in a new window)

    American College of Obstetricians and Gynecologists (ACOG)

    Based on the highest level of evidence found in the data, recommendations are provided and graded according to the following categories:
    Level A - Recommendations are based on good and consistent scientific evidence.
    Level B - Recommendations are based on limited or inconsistent scientific evidence.
    Level C - Recommendations are based primarily on consensus

    Royal College of Obstetricians and Gynaecologists (RCOG)

    RCOG evidence grades
    A Requires at least one randomised controlled trial as part of the body of literature of overall good quality and consistency addressing the specific recommendation.
    B Requires availability of well-conducted clinical studies but no randomised clinical trials on the topic of recommendation.
    C Requires evidence from expert committee reports or opinions and/or clinical experience of respected authorities. Indicates absence of directly applicable studies of good quality.
    Good practice point. Recommended best practice based on the clinical experience of the guideline development group.

    The Society of Obstetricians and Gynaecologists of Canada (SOGC)

    Key to evidence statements and grading of recommendations, using the ranking of the Canadian Task Force on Preventive Health Care
    I: Evidence obtained from at least one properly randomized controlled trial
    II-1: Evidence from well-designed controlled trials without randomization
    II-2: Evidence from well-designed cohort (prospective or retrospective) or case-control studies, preferably from more than one centre or research group
    II-3: Evidence obtained from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments (such as the results of treatment with penicillin in the 1940s) could also be included in this category
    III: Opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees.

    A. There is good evidence to recommend the clinical preventive action
    B. There is fair evidence to recommend the clinical preventive action
    C. The existing evidence is conflicting and does not allow to make a recommendation for or against use of the clinical preventive action; however, other factors may influence decision-making
    D. There is fair evidence to recommend against the clinical preventive action
    E. There is good evidence to recommend against the clinical preventive action
    I. There is insufficient evidence (in quantity or quality) to make a recommendation; however, other factors may influence decision-making.

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