Pre-pregnancy body mass index and adverse maternal and perinatal
outcomes in twin pregnancies: a population based retrospective cohort
study
Abstract
Objectives To assess associations between pre-pregnancy BMI and severe
maternal morbidity (SMM), perinatal death and neonatal morbidity in twin
pregnancies. Design Retrospective cohort study. Setting British
Columbia, Canada (2000-2017). Population All twin births at ≥20 weeks’
gestation. Methods We examined associations between pre-pregnancy BMI,
categorized as underweight (BMI <18.5m/kg2), normal BMI
(18.5m/kg2 BMI <25m/kg2), overweight (25m/kg2 BMI
<30m/kg2) and obese (BMI ≥30m/kg2) and adverse maternal and
perinatal outcomes, using targeted maximum-likelihood estimation,
adjusted for demographics and obstetric history. Outcomes SMM, perinatal
death, severe perinatal morbidity. Results Overall, 7770 (368
underweight, 1704 overweight and 1016 obese) women with twin pregnancy
were included. The rates of SMM (per 10,000 pregnancies) were: 271.1,
320.4, 270.0 and 225.9 in underweight, normal BMI, overweight and obese
women, respectively. Underweight women had higher rates of the composite
perinatal adverse outcome (adjusted rate ratio) [aRR] = 1.79, 95%CI
= 1.32- 2.43), largely driven by increased rates of severe respiratory
distress syndrome, and neonatal death (aRR = 2.81, 95%CI = 1.64-4.83).
There was no evidence of elevated risk for perinatal outcomes among
overweight and obese women. Conclusions In this population-based study
cohort study, we found no evidence of an increased risk of adverse
maternal and perinatal outcomes in overweight and obese women with
twins; however, infants of underweight women are at higher risk of
neonatal death and morbidity. These findings have implications for
pregnancy care of women with twin pregnancies, especially those who are
underweight. Funding SickKids Foundation (SKF-154852) Keywords:
pre-pregnancy obesity, maternal morbidity, perinatal death