Twinning rates and survival of twins in rural Nepal

Background Twin pregnancies are common but there are few data on rates of t winning or survival of liveborn twin infants in developing countries. Methods The rates of multiple births were calculated in a population-based cohort of married women of childbearing age who were enrolled in a randomiz ed community trial to assess the impact of vitamin A or beta-carotene on ma ternal and infant health and survival. Results The rate of twinning was 16.1 per 1000 pregnancies (7.4 if only twi n pregnancies resulting in two liveborn infants were used). The rate for tr iplets and quadruplets was 0.19 and 0.06 per 1000 pregnancies. Twinning rat es were higher among women of higher parity, but were not associated with m aternal age. Twinning rates among twins where at least one was live born (o r increased in utero survival) were 30% (195% CI: -1%, 71%) and 44% (95% CI : 9%, 89%) higher among women receiving vitamin A and beta-carotene supplem ents than placebo, after adjusting for maternal age, gestational age, and p arity. The perinatal mortality rate was 8.54 times higher for twins than si ngletons, 7.32 higher for neonatal mortality, and 5.84 higher for cumulativ e 24-week mortality. This difference was reduced but not erased by adjustin g for gestational age. No difference in survival of liveborn twin infants w as seen by supplement group. A higher mortality rate among male twins was l argely explained by gestational age. Conclusions Multiple births are relatively common occurrences in rural Nepa l, and carry a much higher mortality risk for the infants than for singleto ns. Vitamin A or betacarotene supplementation appeared to increase the rate of twinning, or improve the survival of twins in utero, but did not increa se twin survival after birth.