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BackgroundMaternal obesity is a well-known risk factor for both total preterm birth (PTB) and spontaneous PTB in singleton gestation, whereas this association is not well determined in multiple pregnancy. The objective of this study was to determine the risk of spontaneous PTB according to the pre-pregnancy body mass index (BMI) in twin gestations.MethodsThe association between the risk of PTB and pre-pregnancy BMI was determined in women pregnant with twins between 2004 and 2014. Pre-pregnancy BMI values were divided into three groups (underweight/normal/overweight and obese). PTB was classified as spontaneous PTB (following preterm premature rupture of membranes, preterm labor, or cervical insufficiency) or medically indicated PTB (cesarean section or induction of labor because of maternal/fetal indications).ResultsA total of 1,959 women were included in the analysis, and the percentages of total PTB and spontaneous PTB were 13.1% and 9.3%. The percentages of total PTB and spontaneous PTB in three groups were 14.1%, 11.9%, 16.3%, respectively, and 11.0%, 8.0%, 12.5% (P < 0.05 between normal and overweight/obese women). The risks of total and spontaneous PTB in overweight/obese women were higher than those in women with normal weight, even after adjustment for prior history of PTB, age, maternal height, parity, in vitro fertilization-embryo transfer (IVF-ET) (odds ratio [OR], 1.43; 95% confidence interval [CI], 1.01–2.03; OR, 1.58; 95% CI, 1.05–2.36).ConclusionThe risks of both total and spontaneous PTB were significantly greater in the overweight/obese group than in the normal BMI group.

Objective: It is well known that a short cervix at mid-pregnancy is a risk factor for spontaneous preterm birth in both singleton and twin gestations. Recent evidence also suggests that a long cervix at mid-pregnancy is a predictor of the risk of cesarean section (C/S) in singleton gestation. The purpose of this study was to determine whether a long cervix at mid-pregnancy was associated with an increased risk of C/S in women with twin pregnancies. Methods: We enrolled 746 women pregnant with twins whose cervical length was measured by trans-vaginal ultrasonography at a mean of 22 weeks of gestation and who delivered in our institution. Cases with a short cervix [cervical length (CL) <15 mm] were excluded. Cases were divided into four groups according to the quartile of CL. Results: The rate of C/S increased according to the quartile of CL (47% in the 1st quartile, 51% in the 2nd quartile, 56% in the 3rd quartile and 62% in the 4th quartile, P<0.005, χ2 for trend). CL was an independent risk factor for C/S even after adjustment for confounding variables. When confining analysis to women who delivered after a trial of labor (n=418), to nulliparous women (n=633) or to those who delivered at late preterm or full term (n=666), the rate of C/S also increased according to the quartile of CL, and the relationship between CL and the risk of C/S remained significant after adjustment in each group. Conclusion: In women pregnant with twins, long CL at mid-pregnancy was a risk factor for C/S.

ObjectiveTo investigate whether the uterine artery pulsatility index (UtA PI) of hypertensive pregnancies is higher than that of normal pregnancies in the puerperium, as well as in the antepartum period.MethodsThe UtA PI was measured in hypertensive (group 1) and normal pregnancies (group 2) during antepartum, immediate postpartum or late postpartum periods. Using the transvaginal approach, the bilateral uterine artery indices were measured.ResultsOne hundred twenty-two women were enrolled: group 1, hypertensive disease in pregnancy (11 cases in antepartum, 13 cases in immediate postpartum and 10 cases in late postpartum period); group 2, normal pregnancies (32 cases in antepartum, 29 cases in immediate postpartum and 27 cases in late postpartum). In antepartum and immediate postpartum periods, the mean UtA PI and the proportion of cases with an early diastolic notch were higher in group 1 than in group 2 (antepartum mean UtA PI, 1.14 in group 1 vs. 0.68 in group 2, P<0.001; early diastolic notch, 46% vs. 9%, P<0.05; immediate postpartum mean UtA PI, 1.30 vs. 1.08, P<0.05; early diastolic notch, 85% vs. 48%, P<0.05). In late postpartum period, the mean value of UtA PI of group 1 was still higher than that of group 2, although the proportion of cases with an early diastolic notch was not different (mean UtA PI, 1.43 vs. 1.20, P<0.05; early diastolic notch, 60% vs. 52%, P=0.73).ConclusionThe UtA PI in hypertensive pregnancies was still higher than normal pregnancies in puerperal periods, suggesting that more than several weeks are required to resolve increased uterine artery vascular impedance.

Objective: The purpose of this study was to develop a predictive model for cesarean delivery after induction of labor (IOL) in twin pregnancy. Design: Retrospective cohort study Setting: University hospital. Population: Twin pregnancy who underwent IOL from 2005 to 2018 Methods: The study population was randomly divided into the training and test sets at a ratio of 2:1. Three-fold cross-validation (CV) with 100 times repetitions was applied to select the best model. Main outcome measure to develop and validate a prediction model for cesarean delivery after IOL in twin pregnancies. Results: A total of 1,703 twin pregnancies were analyzed, including 1,356 women in the development cohort of the SNUH database and 347 women in the external validation cohort of the SNUBH database. In the development cohort, the clinical variables that were different between the successful and failed IOL groups were included in the logistic regression analysis, and the final prediction model, composed of five variables (maternal age, maternal height, parity, cervical effacement, and summated birth weight of both twins), was selected with an AUROC of 0.742 (95% confidence interval [CI], 0.700-0.785) and 0.733 (95% CI, 0.671-0.794) in the training set and test set, respectively. A nomogram for predicting the risk of cesarean delivery after IOL in twin pregnancies was also developed. Conclusion: A prediction model to provide information and evaluate the risk of cesarean delivery after IOL in twin pregnancies was developed. Keywords Twin pregnancy, induction of labor, cesarean section, prediction model