Routine Cervical Length Measurement Research Articles

The risk of preterm delivery and pregnancy outcomes in women with asymptomatic short cervix: a retrospective cohort study

Objective Routine cervical length measurement in asymptomatic pregnant women to prevent preterm birth has not been universally adopted due to poor predictive accuracy. The purpose of our study was to evaluate the risk of preterm delivery and pregnancy outcomes in women with asymptomatic short cervix and examine the implications of gestational age at presentation on these outcomes. Study design This was a retrospective cohort study of women with singleton pregnancies who presented prior to or at 32 + 0 weeks with an asymptomatic short cervix (≤25 mm) between April 2014 to March 2018 at a single tertiary maternity center. Women with cervical length ≤25 mm were grouped into four cohorts according to gestational age at presentation: Obstetric outcomes were compared between the cohorts and the general cohort of women delivering during the same period. Outcomes were compared using Mann–Whitney U, chi-square tests, and logistic regression. Survival analysis was carried out to compare the probability of delivery for each subgroup. Results The rate of spontaneous preterm birth <37 weeks was highest in the cohort presenting at 25 + 0–27 + 6 weeks, and lowest in the first cohort presenting at <22 + 0 (60.0 versus 22.2%, p < .05). When compared with the general cohort, the rate of spontaneous preterm birth at <37-week gestation was significantly higher in the asymptomatic short cervix cohort (40.4 versus 8.7%, p < .001), with a 7.1-fold increase in the relative risk of spontaneous PTB. Conclusions In asymptomatic women, cervical shortening showed significant increase in the risk of preterm birth. Our study findings suggest that routine cervical screening may be helpful in predicting risk of preterm birth even in women who are considered low-risk for preterm birth.

Routine second trimester cervical length screening in low risk women identified women at risk of a ‘very’ preterm birth but did not reduce the preterm birth rate: a randomised study from India

Women (n = 300) at ‘low risk’ for a preterm birth (PTB), a singleton pregnancy and for a 16–24 week period of gestation (POG) were randomised to undergo cervical length (CL) measurement by transvaginal sonography (TVS) or not. The aim was to see if routine CL measurement and treatment of a short CL reduced the PTB rate. ‘Low risk’ was defined by an absence of a prior abortion or PTB of a singleton infant (>16 to <37 weeks) due to a spontaneous preterm labour (PTL) or a preterm pre-labour rupture of membranes (pPROM). The PTB rate was similar in the screened and unscreened group (10.3 and 8%, respectively, p = .433). In the screened group, women who delivered at ‘term’ or ‘moderate to late’ preterm (32 to <37 weeks) had a significantly higher mean CL (3.46 ± 0.41 and 3.48 ± 0.65 cm, respectively) than the women who delivered ‘very’ preterm (28 to 31 + 6 weeks; 2.05 ± 0.5 cm; p = .01). A short CL ≤2.5 cm was observed in two primigravidas (2/147 or 1.3%). They delivered at 28 + 3 and 30 + 6 weeks POG, respectively, despite treatment with vaginal progesterone and rescue cerclage in one. Their neonates were discharged in a good condition. In our low risk cohort, a routine second trimester CL measurement did not reduce the overall PTB rate. However, it identified two primigravidas at risk of having a ‘very’ PTB.Clinical Trials Registry (CTRI), India: Registration number CTRI/2016/01/010438Impact statementWhat is already known on this subject? In women with a singleton pregnancy who are at a ‘low risk’ for preterm birth (PTB), a short cervical length (CL) at mid trimester measured by transvaginal sonography (TVS) identifies those at risk for a PTB. This risk may be reduced by the treatment with vaginal progesterone. At present, though evidence in favour of CL measurement in low-risk women exists, it is not established as a part of antenatal care.What do the results of this study add? A routine second trimester CL measurement in low risk women did not reduce the PTB rate. However, screening for a short CL helped to identify two primigravidas at risk for a ’very’ PTB. It may be possible that detection and treatment of a short CL averted an ‘extremely’ PTB (<28 weeks) in these two women.What are the implications of these findings for clinical practice and/or further research? Future studies should assess the outcome of women with a short mid-trimester CL to see whether its treatment resulted in pregnancy prolongation and an improved neonatal outcome.

Is routine transvaginal cervical length measurement cost-effective in a population where the risk of spontaneous preterm birth is low?

A recent meta-analysis has suggested that routine measurement of the cervical length should be performed in conjunction with the anomaly scan to identify a group of women at increased risk of preterm delivery. We decided to investigate whether this recommendation is justifiable in a population where the risk of preterm birth is low. We reviewed 12 years of obstetric data from the Coombe Women and Infants University Hospital. Relative risks of adverse outcomes from the randomized controlled trial were applied and we extrapolated the possible numbers of women requiring intervention. We then used published neonatal data to estimate the cost of neonatal care and estimated the costs of providing the service. Over 12 years from 2000 until 2011, there were 94 646 singleton deliveries, 1776 happening before 34 weeks. Spontaneous onset occurred in 882 (49.7%) of this group. These 882 births were studied. If we apply the figures from a randomized controlled trial, 1609 women (1.7% from our total population) would be expected to have a cervical length 15 mm. If we gave vaginal progesterone to all women with a sonographically short cervix, we would reduce the delivery rate before 34 weeks by 27.7%. The annual costs of providing the service were estimated to be €109 249 and the cost of immediate neonatal care was estimated to be €380 514. Given the implications associated with preterm delivery, routine measurement of cervical length at the time of the anomaly scan may be justifiable from a cost point of view in a population where the risk of preterm birth is low.

Impact of routine transvaginal ultrasound monitoring of cervical length in twins on administration of antenatal corticosteroids

To evaluate whether routine measurement of cervical length (CL) by transvaginal ultrasound (TVU) in twin pregnancies can enable identification of women who will give birth before 34 weeks and require antenatal corticosteroids (ACSs), and whether it can limit their administration to women who will give birth later. Retrospective comparative study in two tertiary referral centers in France. Women with twin gestations followed in two tertiary university hospital maternity units and who delivered from January 1, 2007 to December 31, 2009 were included. In one center, TVU was targeted to women with cases of suspected preterm labor, while the other center used it monthly for all twin pregnancies. The main outcome measure was the administration of a full course of ACS to twins delivered before 34 weeks. Two hundred and seventy women were eligible in the "targeted use" group, and 296 women in the "routine use" group. The rate of administration of at least one full course of ACS for twins born before 34 weeks did not differ between the two groups (85.0% in the targeted use group and 90.0% in the routine use group, P=0.40), but the rate of such administration for those born after 34 weeks was lower in the targeted use group (25.7% vs. 81.2%, P<0.01). On adjusting for confounders using logistic regression modeling, no significant difference in ACS administration before 34 weeks was found between the two groups [adjusted odds ratio (aOR), 0.71, 95% confidence interval (CI), 0.39-1.30]. Routine monitoring performed every month of CL with TVU does not affect the rate of administration of ACS to twins born before 34 weeks, but is associated with a higher rate of such administration for those born later in the specific center of the study.

Do serial measurements of cervical length improve the prediction of preterm birth in asymptomatic women with twin gestations?

Cervical length at midtrimester is a powerful predictor of preterm birth in twin gestations. However, given the fact that, in some cases, cervical shortening may become evident only later during the second trimester, it seems reasonable that serial monitoring of cervical length may improve the detection of preterm birth in women with twins. However, data in support of such a practice are limited and conflicting. The contradictory results may be related to the fact that in most of these studies, the analysis of the predictive value of serial measurements of cervical length was limited to data derived from only two sequential measurements of cervical length, while data on the predictive value of multiple (>2) measurements are scarce. We sought to determine whether serial measurements of cervical length can improve the prediction of preterm birth in asymptomatic women with twin gestations compared with a single measurement of cervical length at midgestation. This was a retrospective cohort study of women with twin pregnancies followed up in a tertiary medical center from 2012 through 2014. All participants underwent routine measurement of cervical length at midgestation and every 2-3 weeks thereafter until 28-32 weeks. For each patient, cervical length was determined at the following time periods: 18+0 to 21+6 weeks (period 1, routine exam), 22+0 to 24+6 weeks (period 2), 25+0 to 27+6 weeks (period 3), and 28+0 to 32+0 weeks (period 4). Measurements of cervical length at periods 2-4 were analyzed in the form of either absolute length (in millimeters) or percent shortening relative to cervical length at period 1. The performance of a stepwise algorithm that incorporated serial measurements of cervical length for the prediction of preterm birth was compared to that achieved with a single measurement of cervical length at period1. Overall, 441 women with twin pregnancies who were eligible for the study underwent a total of 2374 cervical length measurements. The association of a short cervix (<10th percentile) with preterm birth at <32 weeks persisted in each of the 4 periods of gestation [odds ratio (95% confidence interval): 7.2 (3.1-16.5), 15.3 (6.4-36.7), 10.3 (4.4-24.3), and 23.1(8.3-64.1), respectively]. Compared with a single measurement of cervical length at midgestation (period 1), a stepwise algorithm integrating serial cervical length measurements from all 4 successive gestational age periods resulted in a significant increase in the area under the receiver operating characteristic curve (0.917 vs 0.613, P < .001). Similarly, when a target false-positive rate of 5% was used, the same stepwise algorithm was associated with a higher detection rate (69% vs 28%, P < .001), higher positive likelihood ratio (14.54 vs 5.12), and lower negative likelihood ratio (0.32 vs 0.76) for preterm birth at <32 weeks compared with a single measurement of cervical length at period1. Integration of serial measurements of cervical length using a stepwise algorithm in asymptomatic women with twin gestations can improve the detection of women at risk of preterm birth. Prospective studies are needed to validate these findings, and to investigate whether improved risk assessment performance is sufficient to offset the additional costs associated with serial cervical length measurements.

Ultrasound examination at 37 weeks' gestation in the prediction of pregnancy outcome: the value of cervical assessment.

To examine the potential value of routine measurement of cervical length in singleton low-risk pregnancies at 37 weeks of gestation in the prediction of onset and outcome of labor. Cervical length was measured by transvaginal sonography at 37 weeks in 1571 singleton low-risk pregnancies. Outcome measures were gestation at spontaneous onset of labor, post-term delivery, duration of labor and mode of delivery. The median cervical length at 37 weeks was 30 mm and there was a significant association between cervical length and gestation at delivery, which increased from a mean of 38 weeks for cervical length of 10 mm to 41 weeks for cervical length of 35 mm. The incidence of delivery after 40 weeks and 10 days was 296 (18.8%) and the incidence increased with cervical length at 37 weeks from 0% to 6%, 35% and 68% for respective cervical lengths of < 20, 21-30, 31-40 and 41-50 mm. In the pregnancies with spontaneous onset of labor the incidence of Cesarean section for failure to progress increased from 3.6% to 6.0%, 6.4% and 11.8% for cervical lengths of < 20, 21-30, 31-40 and 41-50 mm, respectively. In the pregnancies requiring induction for post-term the incidence of Cesarean section for failed induction or failure to progress increased from 7.5% to 20.1% to 25.0% for cervical lengths of 21-30, 31-40 and 41-50 mm, respectively. Measurement of cervical length at 37 weeks can define the likelihood of spontaneous delivery before 40 weeks and 10 days and the risk of Cesarean section in those requiring induction for prolonged pregnancy.

Cervical length at 23 weeks of gestation: relation to demographic characteristics and previous obstetric history.

To examine the feasibility of introducing routine measurement of cervical length at 23 weeks of gestation, to establish the distribution of cervical lengths in a routine population of singleton pregnancies and to examine the relation between cervical length and demographic characteristics and previous obstetric history. Cervical length was measured by transvaginal sonography at 23 weeks of gestation in women with singleton pregnancies attending for routine antenatal care. The distribution of cervical lengths was established and the significance of differences in median cervical length between subgroups according to maternal age, ethnic origin, maternal ponderal index, cigarette smoking, alcohol drinking, drug abuse and previous obstetric history was calculated. In addition, 100 women were asked to complete a questionnaire aimed to assess the degree of discomfort, pain or embarrassment caused by the scan. In 100 pregnancies, cervical length was measured in each patient by two of four operators to determine intraobserver and interobserver variabilities. During the study period, 2702 (80%) of the 3358 women attending for a 23-week scan agreed to participate in the study and, in all cases, the cervical length was measured successfully. The median cervical length was 38 mm and in 1.6% of cases the length was 15 mm or less. More than 90% of the women reported that the procedure was associated with no or only mild discomfort and embarrassment, whilst 85% found the ultrasound scan to be equally or less uncomfortable than a speculum examination. Measurement of cervical length was highly reproducible and, on 95% of occasions, the difference between two measurements by the same observer and by two observers was < or = 3.5 mm and < or = 4.2 mm, respectively. Cervical length was significantly shorter in women of Afro-Caribbean origin compared to Caucasians, those aged less than 20 years, those with a low ponderal index, those with a history of previous miscarriage or preterm delivery and in drug abusers. Transvaginal sonographic measurement of cervical length is highly reproducible and it is associated with a minimal degree of discomfort to the patients. At 23 weeks, the median cervical length is 38 mm and, in 1.6% of the population, the length is 15 mm or less. There is an association between cervical length and demographic characteristics and previous obstetric history.

Cervical length at 23 weeks of gestation: prediction of spontaneous preterm delivery.

To examine the potential value of routine measurement of cervical length in singleton pregnancies at 23 weeks of gestation in the prediction of the risk for early spontaneous preterm delivery. Cervical length was measured by sonography at 23 weeks in 2567 singleton pregnancies in women attending for routine antenatal care. In 43 women, the length was < or = 15 mm and 21 of these were managed expectantly, whereas in 22 cases a cervical cerclage was placed. In the pregnancies that were managed expectantly, the relation between cervical length and preterm delivery was examined and the risk of spontaneous delivery at < or = 32 weeks was estimated. Cervical length at 23 weeks was < or = 15 mm in 1.7% of cases; this group contained 86%, 58% and 20% of pregnancies that delivered spontaneously at < or = 28, < or = 32 and < or = 36 weeks, respectively. The risk for delivery at < or = 32 weeks decreased from 78% at a cervical length of 5 mm to 4% at 15 mm and 0.5% at 50 mm. Cervical length at 23 weeks is < or = 15 mm in < 2% of the population; this group contains about 90% and 60% of the women delivering at < or = 28 and < or = 32 weeks, respectively. Measurement of cervical length provides accurate prediction of risk for early preterm delivery.