The capacity of mid-pregnancy cervical length to predict preterm birth in low-risk women: a national cohort study.

INTRODUCTION: We investigated the predictive capacity of mid-trimester cervical length (CL) measurement for spontaneous and iatrogenic preterm birth. MATERIAL AND METHODS: We performed a prospective observational cohort study in nulliparous women and low-risk multiparous women with a singleton pregnancy between 16(+0) and 21(+6) weeks of gestation. We assessed the prognostic capacity of transvaginally measured mid-trimester CL for spontaneous and iatrogenic preterm birth (<37 weeks) using likelihood ratios (LR) and receiver-operating-characteristic analysis. We calculated numbers needed to screen to prevent one preterm birth assuming different treatment effects. Main outcome measures were preterm birth <32, <34 and <37 weeks. RESULTS: We studied 11,943 women, of whom 666 (5.6%) delivered preterm: 464 (3.9%) spontaneous and 202 (1.7%) iatrogenic. Mean CL was 44.1 mm (SD 7.8 mm). In nulliparous women, the LRs for spontaneous preterm birth varied between 27 (95% CI 7.7-95) for a CL ≤ 20 mm, and 2.0 (95% CI 1.6-2.5) for a CL between 30 and 35 mm. For low-risk multiparous women, these LRs were 37 (95% CI 7.5-182) and 1.5 (95% CI 0.97-2.2), respectively. Using a cut-off for CL ≤ 30 mm, 28 (6.0%) of 464 women with spontaneous preterm birth were identified. The number needed to screen to prevent one case of preterm birth was 618 in nulliparous women and 1417 for low-risk multiparous women (40% treatment effect, cut-off 30 mm). CONCLUSION: In women at low risk of preterm birth, CL predicts spontaneous preterm birth. However, its isolated use as a screening tool has limited value due to low sensitivity.

Preventing Preterm Birth with Progesterone in Women with a Short Cervical Length from a Low-Risk Population: A Multicenter Double-Blind Placebo-Controlled Randomized Trial.

OBJECTIVE: The objective of this study was to evaluate the effectiveness of vaginal progesterone in reducing adverse neonatal outcome due to preterm birth (PTB) in low-risk pregnant women with a short cervical length (CL). STUDY DESIGN: Women with a singleton pregnancy without a history of PTB underwent CL measurement at 18 to 22 weeks. Women with a CL ≤ 30 mm received vaginal progesterone or placebo. Primary outcome was adverse neonatal outcome, defined as a composite of respiratory distress syndrome, bronchopulmonary dysplasia, intracerebral hemorrhage > grade II, necrotizing enterocolitis > stage 1, proven sepsis, or death before discharge. Secondary outcomes included time to delivery, PTB before 32, 34, and 37 weeks of gestation. Analysis was by intention to treat. RESULTS: Between 2009 and 2013, 20,234 women were screened. A CL of 30 mm or less was seen in 375 women (1.8%). In 151 women, a CL ≤ 30 mm was confirmed with a second measurement and 80 of these women agreed to participate in the trial. We randomly allocated 41 women to progesterone and 39 to placebo. Adverse neonatal outcomes occurred in two (5.0%) women in the progesterone and in four (11%) women in the control group (relative risk [RR], 0.47; 95% confidence interval [CI], 0.09-2.4). The use of progesterone resulted in a nonsignificant reduction of PTB < 32 weeks (2.0 vs. 8.0%; RR, 0.33; 95% CI, 0.04-3.0) and < 34 weeks (7.0 vs. 10%; RR, 0.73; 95% CI, 0.18-3.1) but not on PTB < 37 weeks (15 vs. 13%; RR, 1.2; 95% CI, 0.39-3.5). CONCLUSION: In women with a short cervix, who are otherwise low risk, we could not show a significant benefit of progesterone in reducing adverse neonatal outcome and PTB.

Preventing preterm birth with progesterone: costs and effects of screening low risk women with a singleton pregnancy for short cervical length, the Triple P study.

BACKGROUND: Women with a short cervical length in mid-trimester pregnancy have a higher risk of preterm birth and therefore a higher rate of neonatal mortality and morbidity. Progesterone can potentially decrease the number of preterm births and lower neonatal mortality and morbidity. Previous studies showed good results of progesterone in women with either a history of preterm birth or a short cervix. However, it is unknown whether screening for a short cervix and subsequent treatment in mid trimester pregnancy is effective in low risk women. METHODS/DESIGN: We plan a combined screen and treat study among women with a singleton pregnancy without a previous preterm birth. In these women, we will measure cervical length at the standard anomaly scan performed between 18 and 22 weeks. Women with cervical length ≤ 30 mm at two independent measurements will be randomly allocated to receive either vaginal progesterone tablets or placebo between 22 and 34 weeks. The primary outcome of this trial is adverse neonatal condition, defined as a composite outcome of neonatal mortality and severe morbidity. Secondary outcomes are time to delivery, preterm birth rate before 32, 34 and 37 weeks, days of admission in neonatal intensive care unit, maternal morbidity, maternal admission days for preterm labour and costs. We will assess growth, physical condition and neurodevelopmental outcome of the children at two years of age. DISCUSSION: This study will provide evidence for the usefulness and cost-effectiveness of screening for short cervical length at the 18-22 weeks and subsequent progesterone treatment among low risk women. TRIAL REGISTRATION: Netherlands Trial Register (NTR): NTR207.

Is asymptomatic bacteriuria associated with short cervical length in women with a singleton pregnancy, a secondary analysis of two national cohort studies with small embedded randomized controlled trials.

OBJECTIVE: To assess the association between asymptomatic bacteriuria (ASB) and short cervical length (CL), since they are both associated with preterm delivery. STUDY DESIGN: In two prospective multicentre cohort studies, pregnant women were screened for the presence of ASB and short CL (≤25 mm). We compared CL in women with and without ASB. Both studies had a small randomised clinical trial embedded. RESULTS: Our study population comprised 1 610 women, of whom 114 were ASB positive. Median cervical length was similar in women with and without ASB (44.0 vs 44.0 mm, P = 0.60). More women in the ASB positive group had a short CL compared to the ASB negative group (1.8 % versus 0.4 %, P = 0.047)). The gestational age at delivery did not differ between the groups (ranging from 38 + 3 in women with ASB and short CL to 39 + 5 in women without ASB with a short CL P = 0.52). No preterm births occurred in women with a short cervical length (regardless of ASB status). In the women without ASB and no short CL 4.8 % had a preterm birth, in the women with ASB but not a short CL 4.1 % had a preterm birth. CONCLUSION: While ASB status did not influence median cervical length, we found a significant relationship between a short CL and ASB positive women. We found no statistical significant difference on the preterm birth rate and mean gestational age.

Repeated cervical length measurements for the verification of short cervical length.

OBJECTIVE: To determine if the verification of short cervical length with a repeated measurement improved the identification of patients with short cervical length at increased risk of preterm delivery. METHODS: The present secondary analysis analyzed prospective cohort study data from patients with singleton pregnancies without a history of preterm delivery who presented for obstetric care in the Netherlands and delivered between November 18, 2009, and January 1, 2013. Cervical length was measured during standard anomaly scan and a second measurement was performed if the cervical length was 30 mm of shorter. Logistic regression and Cox proportional hazards modeling were used to evaluate associations between cervical length measurements and spontaneous preterm delivery before 37 weeks of pregnancy. RESULTS: Cervical length measurements from 12 358 patients were included; 221 (1.8%) had an initial cervical length measurement of 30 mm or shorter. A second cervical length measurement was performed for 167 (75.6%) patients; no differences were identified in the odds of spontaneous preterm delivery when evaluated using the first, second, or a mean of both measurements, regardless of whether cervical length was analyzed as a continuous or dichotomous variable. CONCLUSION: Among patients with singleton pregnancies, verification of short cervical length did not improve the identification of short cervical length.