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Data on the optimal gestational weight gain in twin pregnancies are limited. As a result, the Institute of Medicine currently provides only provisional recommendations on gestational weight gain in this population.This study aimed to identify the optimal range of gestational weight gain in twin pregnancies and to estimate the association between inappropriate gestational weight gain and adverse pregnancy outcomes.This was a retrospective cohort study of all women with twin pregnancies that were followed up in a single, tertiary center between 2000 and 2014. We used 2 approaches to identify the optimal range of gestational weight gain: a statistical approach (the interquartile range of gestational weight gain in low-risk pregnancies with normal outcomes) and an outcome-based approach (by identifying thresholds of gestational weight gain below or above which the rate of adverse outcomes increases). The primary outcome was preterm birth. Associations of gestational weight gain below or above the normal range with the study outcomes were estimated using logistic regression analysis and were expressed as adjusted odds ratio with 95% confidence intervals. These associations were stratified by prepregnancy body mass index group.A total of 1274 women with twin pregnancies met the study criteria: 43 were classified as underweight, 777 were normal weight, 278 were overweight, and 176 were obese. Our estimates of the optimal gestational weight gain range were similar to those recommended by the Institute of Medicine except for the obese category, in which our optimal gestational weight gain range at 37 weeks (9.3-16.3 kg) was lower than in the provisional Institute of Medicine recommendations (11.3-19.1 kg). Nearly half of our cohort experienced inappropriate gestational weight gain: 30% (n=381) gained weight below and 17% (n=216) gained weight above current Institute of Medicine recommendations. In the normal weight group, gestational weight gain below recommendations was associated with an increased risk of preterm birth and birthweight at the10th centile and with a reduction in the risk of hypertensive disorders, whereas gestational weight gain above recommendations was associated with an increased risk of hypertensive disorders and a reduction in the risk of birthweight at the10th centile. Associations were less consistent in the overweight and obese groups.These findings identify gestational weight gain as a potentially modifiable risk factor for preterm birth and other pregnancy complications in twin gestations. Further prospective studies are needed to determine whether interventions aimed at optimizing gestational weight gain can improve the outcomes of these high-risk pregnancies.

Background Among singleton pregnancies, gestational diabetes mellitus is associated with adverse outcomes. In twin pregnancies, this association may be attenuated, given the higher rate of prematurity and the a priori increased risk of some of these complications. Objective Our aim was to test the hypothesis that gestational diabetes mellitus is less likely to be associated with adverse pregnancy outcomes in twin compared with singleton gestations. Methods This retrospective cohort study comprised all twin and singleton live births in Ontario, Canada, 2012–2016. Pregnancy outcomes were compared between women with vs without gestational diabetes mellitus, analyzed separately for twin and singleton births. Adjusted risk ratios and 95% confidence intervals were generated using modified Poisson regression, adjusting for maternal age, nulliparity, smoking, race, body mass index, preexisting hypertension, and assisted reproductive technology. Results A total of 270,843 women with singleton (n = 266,942) and twin (n = 3901) pregnancies met the inclusion criteria. In both the twin and singleton groups, gestational diabetes mellitus was associated with (adjusted risk ratio, [95% confidence interval]) cesarean delivery (1.11 [1.02–1.21] and 1.20 [1.17–1.23], respectively) and preterm birth at Conclusion In contrast to singleton pregnancies, gestational diabetes mellitus in twins was not associated with hypertensive complications and certain neonatal morbidities. Still, the current study highlights that gestational diabetes mellitus is associated with some adverse pregnancy outcomes including accelerated fetal growth also in twin pregnancies.

In women with gestational diabetes mellitus, it is not clear whether routine induction of labor at40 weeks of gestation is beneficial to mother and newborn infant.The purpose of this study was to compare outcomes among women with gestational diabetes mellitus who had induction of labor at either 38 or 39 weeks with those whose pregnancy was managed expectantly.We included all women in Ontario, Canada, with diagnosed gestational diabetes mellitus who had a singleton hospital birth at ≥38 + 0 weeks of gestation between April 2012 and March 2014. Data were obtained from the Better Outcomes RegistryNetwork Ontario, which is a province-wide registry of all births in Ontario, Canada. Women who underwent induction of labor at 38 + 0 to 38 + 6 weeks of gestation (38-IOL; n = 1188) were compared with those who remained undelivered until 39 + 0 weeks of gestation (38-Expectant; n = 5229). Separately, those women who underwent induction of labor at 39 + 0 to 39 + 6 weeks of gestation (39-IOL; n = 1036) were compared with women who remained undelivered until 40 + 0 weeks of gestation (39-Expectant; n = 2162). Odds ratios and 95% confidence intervals were adjusted for maternal age, parity, insulin treatment, and prepregnancy body mass index.Of 281,480 women who gave birth during the study period, 14,600 women (5.2%) had gestational diabetes mellitus; of these, 8392 women (57.5%) met all inclusion criteria. Compared with the 38-Expectant group, those women in the 38-IOL group had lower odds for cesarean delivery (adjusted odds ratio, 0.73; 95% confidence interval, 0.52-0.90), higher odds for neonatal intensive care unit admission (adjusted odds ratio, 1.36; 95% confidence interval, 1.09-1.69), and no difference in other maternal-newborn infant outcomes. Compared with the 39-Expectant group, women in the 39-IOL group likewise had lower odds for cesarean delivery (adjusted odds ratio, 0.73; 95% confidence interval, 0.58-0.93) but no difference in neonatal intensive care unit admission (adjusted odds ratio, 0.83; 95% confidence interval, 0.61-1.11).In women with gestational diabetes mellitus, the routine induction of labor at 38 or 39 weeks is associated with a lower risk of cesarean delivery compared with expectant management but may increase the risk of neonatal intensive care unit admission when done at39 weeks of gestation.