Study design
This retrospective study included 2,586 pregnant women delivering twins between 2005 and 2020 at the Buergerhospital in Frankfurt, Germany. Thereof, 2,449 women fulfilled the two primary inclusion criteria, diamnionicity and an available pre-pregnancy BMI (calculated as weight [kg] divided by the square of height [m2]) and were analyzed for maternal outcomes.
For the neonatal analysis, 246 twin pairs of mothers being analyzed were excluded because of gestational age less than 24 weeks, stillbirth, congenital malformation, twin-to-twin transfusion syndrome, twin anemia polycythemia sequence, medically indicated abortions and hospitalization for less than 72 hours after birth.
The mothers were subdivided according to their pre-pregnancy BMI based on WHO standards (underweight <18.5 kg/m2, normal weight 18.5 – 24.9 kg/m2, overweight 25 – 29.9 kg/m2, obese ≥30 kg/m2, obesity class I 30 – 34.9 kg/m2, obesity class II 35 – 39.9 kg/m2 and obesity class III ≥40 kg/m2). The obese group consisted of 265 women, whereof 171 were in obesity class I, 58 in obesity class II and 36 in obesity class III.