Outcome of small for gestational age preterm singletons: a population-based cohort study.

OBJECTIVE: To examine the outcomes of births among small and appropriate for gestational age (SGA and AGA) infants by gestational age and maternal characteristics. MATERIALS AND METHODS: We used a national perinatal registry to compare the selected maternal and neonatal outcomes between AGA and SGA neonates born at gestational age groups 33-36, 30-32, 28-29, and <28 weeks. We evaluated maternal body mass index (BMI), pre-gestational/gestational diabetes, hypertensive disorders, and cesarean births as well as frequencies of 5-min Apgar score <7, intraventricular hemorrhage (IVH), respiratory distress syndrome (RDS), the need for assisted ventilation, and early neonatal deaths. RESULTS: We evaluated 159,774 AGA (8871 preterm) and 13,735 SGA (1147 preterm) infants and found a gradual decrease in the incidence of SGA infants with increasing gestational age. Diabetes was unrelated to having an SGA or AGA infant among preterm births, but the odds ratio (OR) for preeclampsia among preterm-SGA pregnancies was up to 6.9 (95% CI 3.8, 12.5) at <28 weeks. SGA infants fare worse compared to AGA neonates in every parameter tested but only in preterm births >30 weeks. CONCLUSIONS: Being SGA further complicates preterm births after 30 weeks of gestation but not earlier. This might suggest that an extended period in the hostile intrauterine environment, or that being born at <30 weeks, is bad enough and is not further aggravated by being SGA.

Respiratory morbidity in twins by birth order, gestational age and mode of delivery.

OBJECTIVE: To evaluate the relationship between respiratory morbidity in twins by gestational age, birth order and mode of delivery. METHODS: All twin deliveries at <37 weeks, registered in a national database, in the period 2003-2012 were classified into four gestational age groups: 33-36, 30-32, 28-29, and <28 weeks. Outcome variables included transient tachypnea of the newborn (TTN), respiratory distress syndrome (RDS) and need for assisted ventilation. RESULTS: A total of 1836 twins were born vaginally, and 2142 twins were born by cesarean delivery, for a grand total of 3978 twins. TTN did not appear to be related to birth order and to the mode of delivery. In contrast, RDS was more frequent among the second born twins in the vaginal birth groups born at 30-36 weeks [odds ratio (OR) 2.5, 95% confidence interval (CI) 1.2-5.1 and OR 2.0, 95% CI 1.2-3.5 for 33-36 weeks and 30-32 weeks, respectively], whereas this trend was seen in the cesarean birth groups born earlier (OR 3.8, 95% CI 1.1-13.0 for 28-29 weeks). Cesarean delivery significantly increased the frequency of RDS in twin A as well as in twin B compared with vaginal birth, but only at gestational ages <30 weeks. CONCLUSION: Mode of delivery and birth order have a gestational age dependent effect on the incidence of RDS.

Hypertensive disorders during monozygotic and dizygotic twin gestations: A population-based study.

OBJECTIVE: To determine whether the incidence of hypertensive disorders is different in monozygotic compared to dizygotic twin pregnancies. METHODS: A registry-based survey of twin pregnancies delivered during 2003 to 2012. We used the best clinical estimate of zygosity based on the concept that all monochorionic twins are monozygotic and all unlike-sex pairs are dizygotic, thus excluding same-sex dichorionic twin gestations for which zygosity cannot be ascertained on clinical grounds. Study cohorts were twin pregnancies with or without preeclampsia and gestational hypertension. RESULTS: A total of 3419 twin gestations met the inclusion criteria, of which 442 (12.9%) were monochorionic and 1255 (36.7%) were unlike-sex twins, excluding 1722 same-sex dichorionic twin gestations (50.4%). There was no significant difference in the incidence of preeclampsia (OR: 0.9; 95% CI: 0.4-2.0 for monozygotic males and OR: 0.6; 95% CI: 0.3-1.4 for monozygotic females) and gestational hypertension (OR: 0.7; 95% CI: 0.2-2.5 for monozygotic males, and OR: 0.7; 95% CI: 0.2-2.3 for monozygotic females) between monochorionic and unlike-sex pairs. Maternal prepregnancy obesity and nulliparity were the only significant associated factors of preeclampsia (OR: 3.8; 95% CI: 2.0-7.0, and OR: 2.5; 95% CI: 1.4-4.4, respectively). Maternal prepregnancy obesity (OR: 5.5; 95% CI: 2.5-12.2), maternal age ≥36 years (OR: 2.5; 95% CI: 1.1-6.1), and family history of hypertension (OR: 2.6; 95% CI: 1.3-5.1) were significantly associated with gestational hypertension. CONCLUSION: Based on a large population-based dataset and on the best clinical estimate of twin zygosity, it appears that zygosity is not associated with hypertensive disorders in twin gestations.