Although shortened cervical length has been consistently associated with spontaneous preterm birth, it is not known when in gestation this risk factor becomes apparent.
Objective
To determine whether sonographic cervical findings between 16 weeks' and 18 weeks 6 days' gestation predict spontaneous preterm birth and whether serial evaluations up to 23 weeks 6 days' gestation improve prediction in high-risk women.
DESIGN, SETTING, AND
Participants
Blinded observational study performed between March 1997 and November 1999 at 9 university-affiliated medical centers in the United States in 183 women with singleton gestations who previously had experienced a spontaneous birth before 32 weeks' gestation.
OBSERVATION: Certified sonologists performed 590 endovaginal sonographic examinations at 2-week intervals. Cervical length was measured from the external os to the functional internal os along a closed endocervical canal. Funneling and dynamic cervical shortening were also recorded.
Main Outcome Measure
Spontaneous preterm birth before 35 weeks' gestation, analyzed by selected cutoff values of cervical length.
Results
Forty-eight women (26%) experienced spontaneous preterm birth before 35 weeks' gestation. A cervical length of less than 25 mm at the initial sonographic examination was associated with a relative risk (RR) for spontaneous preterm birth of 3.3 (95% confidence interval [CI], 2.1-5.0; sensitivity = 19%; specificity = 98%; positive predictive value = 75%). After controlling for cervical length, neither funneling (P =.24) nor dynamic shortening (P =.054) were significant independent predictors of spontaneous preterm birth. However, using the shortest ever observed cervical length on serial evaluations, after any dynamic shortening, the RR of a cervical length of less than 25 mm for spontaneous preterm birth increased to 4.5 (95% CI, 2.7-7.6; sensitivity = 69%; specificity = 80%; positive predictive value = 55%). Compared with a single cervical measurement at 16 weeks' to 18 weeks 6 days' gestation, serial measurements at up to 23 weeks 6 days significantly improved the prediction of spontaneous preterm birth in a receiver operating characteristic curve analysis (P =.03).
Conclusions
Cervical length assessed by endovaginal sonography between 16 weeks' and 18 weeks 6 days' gestation, augmented by serial evaluations, predicts spontaneous preterm birth before 35 weeks' gestation in high-risk women.
endovaginal sonography cervical length preterm birth prediction, short cervix mid-trimester ultrasound spontaneous preterm delivery, serial cervical length measurements high risk pregnancy, cervical funneling dynamic shortening preterm birth risk, cervical length less than 25mm preterm birth sensitivity specificity, Owen cervical sonography preterm birth prediction, second trimester transvaginal ultrasound cervix preterm labor, receiver operating characteristic cervical length serial measurement, 16 to 24 weeks cervical assessment high risk women, blinded observational study cervical length spontaneous preterm birth
PMID 11560539 11560539 DOI 10.1001/jama.286.11.1340 10.1001/jama.286.11.1340 Owen et al. 2001, Owen 2001
Cite this article
Owen, J., Yost, N., Berghella, V., Thom, E., Swain, M., Dildy, G. A., Miodovnik, M., Langer, O., Sibai, B., McNellis, D., National Institute of Child Health and Human Development, & Maternal-Fetal Medicine Units Network (2001). Mid-trimester endovaginal sonography in women at high risk for spontaneous preterm birth. JAMA, 286(11), 1340-1348. https://doi.org/10.1001/jama.286.11.1340
Owen J, Yost N, Berghella V, Thom E, Swain M, Dildy GA, et al. Mid-trimester endovaginal sonography in women at high risk for spontaneous preterm birth. JAMA. 2001;286(11):1340-1348. doi:10.1001/jama.286.11.1340
Owen, J., et al. "Mid-trimester endovaginal sonography in women at high risk for spontaneous preterm birth." JAMA, vol. 286, no. 11, 2001, pp. 1340-1348.
We sought to determine the predictive accuracy for preterm delivery of transvaginal ultrasonography of the cervix between 14 and 24 weeks' gestation in high-risk patients and to determine whether cerclage prevents preterm delivery in patients with ultrasonographic cervical changes. Patients with asymptomatic singleton pregnancies at high risk for preterm delivery were followed prospectively from 14 weeks' to 23 weeks 6 days' gestation with transvaginal ultrasonography of the cervix. The subgroup of patients with either a cervical length of <25 mm or funneling of >25% or both was offered McDonald salvage cerclage, which was performed at the discretion of the patient and the obstetrician. The 2 groups (with and without cerclage) were compared for the primary outcome of preterm delivery at <35 weeks' gestation. One hundred sixty-eight women were followed, including 97 (58%) with >/=1 prior 14- to 34-week preterm deliveries. Of 63 (37. 5%) patients identified as having cervical changes, 23 (37%) had preterm delivery; of 105 patients with no cervical changes, 8 (8%) had preterm delivery (relative risk, 4.8; 95% confidence interval, 2. 3-10.1). The sensitivity, specificity, and positive and negative predictive values of either a short cervix of <25 mm or funneling of >25% or both were 74%, 70%, 37%, and 92%, respectively. Of 63 pregnancies in which there were cervical changes, 39 underwent cerclage and 24 did not. These 2 groups were similar for demographic characteristics, risk factors, and transvaginal ultrasonographic cervical length and funneling but dissimilar for gestational age at identification of cervical changes (18.3 vs 21.2 weeks' gestation in the groups with and without cerclage, respectively; P <.001). Multivariate logistic regression analysis after adjustment for gestational age at cervical changes showed no difference in the rate of preterm delivery between the groups with and without cerclage (odds ratio, 1.1; 95% confidence interval, 0.3-4.6). Stratified analysis of patients identified between 18 and 24 weeks revealed 22 pregnancies with cerclage and 22 pregnancies without cerclage, which was similar for all characteristics studied. The incidence of preterm delivery remained similar (27% vs 23%, respectively; P =.7), as did days from cervical changes to delivery (111 vs 96, respectively; P =.2). Transvaginal ultrasonography of the cervix between 14 and 24 weeks' gestation is a good predictor of preterm delivery in high-risk pregnancies. Cerclage may not prevent preterm delivery in patients identified to be at high risk for this outcome by transvaginal ultrasonography.
To establish a nomogram for the length of the uterocervical canal and to determine whether this can be used to predict preterm delivery. Cervical length was measured by transvaginal ultrasonography in 32 women (21 primigravid, 11 multigravid) with threatened preterm delivery, and in 177 normal singleton pregnancies between 18-37 weeks' gestation. Regression analysis was used to create the nomogram. Student t test was used to compare the groups. A linear relationship was found between cervical length and gestational age (r = -0.4, P < .001). Comparison of cervical length on admission in the patients with threatened preterm delivery showed that 11 preterm deliveries occurred in women who had a mean cervical length of 23.2 mm (range 17-29), whereas 21 term deliveries occurred in women with a mean cervical length of 31.7 mm (range 21-42). The difference was significant (P < .001). A cervical length of less than 20 mm on admission had a positive predictive value of 100%. These patients had preterm delivery despite tocolytic therapy during hospitalization. The risk of preterm delivery is high in women whose cervical length on admission is less than 30 mm, and strict management is required for those with a cervical length of less than 20 mm.
Preston M et al., 2024·European journal of obstetrics, gynecology, and reproductive biology·
Open Access
Preterm Birth (delivery before 37 weeks of gestation) is the leading cause of childhood mortality and is also associated with significant morbidity both in the neonatal period and beyond. The aetiology of spontaneous preterm birth is unclear and likely multifactorial incorporating factors such as infection/inflammation and cervical injury. Placental insufficiency is emerging as an additional contributor to spontaneous preterm delivery; however, the mechanisms by which this occurs are not fully understood. Serum biomarkers and imaging techniques have been investigated as potential predictors of placental insufficiency, however none have yet been found to have a sufficient predictive value. This review examines the evidence for the role of the placenta in preterm birth, preterm prelabour rupture of the membranes and abruption as well as highlighting areas where further research is required.
Qin XD et al., 2023·Environmental health perspectives
Estrogens play a critical role in parturition, and poly- and perfluoroalkyl substances (PFAS), which have estrogenic effects, have been associated with preterm birth. However, the impact of estrogens on the association between PFAS and preterm birth is unknown. The objective of this study is to investigate if estrogens modified the association between PFAS and preterm birth, using a nested case-control study design. A total of 371 preterm births and 508 controls were selected from a birth cohort study in China between 2016 and 2018. Perfluorobutanoic acid (PFBA), perfluorohexanesulfonic acid (PFHxS) and its branched isomer, perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS) and its branched isomer, and perfluorononanoic acid (PFNA) were quantified in maternal serum (mean gestational age of 32 wk). Estradiol and estriol were quantified in cord serum. Preterm birth was defined as live delivery at <37 gestational weeks. Causal mediation analysis was used to estimate the mediation and interaction effects of estrogen on the association between PFAS and preterm birth. Latent profile analysis was used to identify important estrogen profiles. Multiple linear regression was used to estimate associations between PFAS and preterm birth and interactions between PFAS and estrogens on preterm birth. Overall, higher odds ratios (ORs) of preterm birth were associated with each 1 ln-unit PFAS increase: PFBA [1.20, 95% confidence interval (CI): 1.14, 1.26], PFNA (1.30, 95% CI: 1.21, 1.39), PFOA (1.98, 95% CI: 1.54, 2.55), and PFOS (1.91, 95% CI: 1.76, 2.07) and its branched isomer (1.91, 95% CI: 1.90, 1.92). We detected statistically significant interactions between cord estradiol and PFAS on preterm birth, while no mediation effects of cord estrogen were observed. The ORs of PFOS (4.29, 95% CI: 1.31, 8.25), its branched isomer (6.71, 95% CI: 1.06, 11.91), and preterm birth were greater for participants with high cord estrogen levels than for participants with low cord estrogen levels. Our findings suggest that estrogen modified the association between maternal PFAS exposure and preterm birth. Further studies on maternal PFAS exposure and preterm birth, taking interaction effects of cord estrogens into account, are warranted. https://doi.org/10.1289/EHP11377.