Gestational age, morbidity and mortality among twin births in New South Wales, Australia 2003-2014: A cohort study

Background Evidence suggests that the trend toward early planned births observed among singletons may be evident among twin pregnancies. Aims To describe trends in gestational age at birth, pregnancy characteristics, neonatal morbidity and mortality among twin pregnancies. Materials and Methods Population-based data linkage study of twin births of >= 30 weeks of gestation without a major congenital anomaly born in 2003-2014 in New South Wales (NSW), Australia. Linked pregnancy and birth, hospital and mortality data were used. Generalised linear regression was used to assess linear trends. Risk difference (RD) and 95% confidence intervals were estimated. Results Among 28 076 eligible twin births (14 038 pregnancies), 49% of births occurred prior to 37 weeks and 69% of births were planned (pre-labour caesarean or induction of labour). There were increases over time in the proportion of twin births at preterm gestations (30-34 weeks (RD 2.1, 95% CI 0.1, 4.0), 35-36 weeks (RD 7.5, 95% CI 5.4, 9.7)) and in the rates of planned births (pre-labour caesarean (RD 6.4, 95% CI 4.0, 8.8), induction (RD 4.6, 95% CI 2.6, 6.6)). There was no significant change in stillbirth or neonatal death rates, but there was an increase in neonatal morbidity over the study period. Concurrently, there were increases in the prevalence of gestational diabetes; and decreases in pregnancy hypertension, assisted reproductive technology use, small-for-gestational age and birthweight discordance. Conclusions Gestational age at birth among twin births is decreasing and birth intervention is increasing. There are increasing rates of neonatal morbidity, but no overall change in perinatal mortality.