Respiratory distress in heavier versus lighter twins

We performed a retrospective study of twin pairs under 36 weeks gestation admitted to a regional neonatal unit over a three year period to determine if the larger twin of a twin pair is at increased risk of respiratory distress in the immediate postnatal period compared to the smaller twin. Gestation, gender, birth weight, mode and reason for delivery, birth order, and Apgar at 5 minutes were correlated with the need for added oxygen at 4 hours, the need for ventilation, oxygen requirement at 28 days and mortality. One hundred and twenty-four twin pairs were analyzed with a median gestation of 31 weeks (range 23-35). There were 47 female-female pairs, 40 male-male pairs and 37 mixed pairs. Multiple logistic regression revealed no significant increased risk for ventilation in male, heavier or second twins. The need for oxygen at 4 hours was strongly associated with being male and being the second twin, but not with being the heavier twin. However, on analysis of twins of 28 weeks gestation or above a significant association was found between a persisting oxygen requirement at 4 hours and being male (OR 2.2; 95% CI 1.15-4.16), being the heavier twin (OR 1.9; 95% CI 1.03-3.46), and being the second twin (OR 2.7; 95% CI 1.48-4.99). No association was found between mortality and being male, and being the second or smaller twins.

Heavier twins above 28 weeks gestation are at increased risk of short term mild respiratory problems following delivery compared to lighter twins at the same gestation. This is not as strong a factor as birth order or male gender, but it is important to be aware of this in antenatal counselling of the parents as the smaller twin is usually perceived to be at greater risk of morbidity.