Maternal birthweight and outcome of twin pregnancy

The definitive version is available at www.blackwell-synergy.comThere is evidence from singletons that maternal birthweight is positively related to offspring gestational length and birthweight, and some evidence of an inverse relationship with preterm birth. Among twins very preterm birth is the major cause of neonatal mortality and of immediate and later morbidity, including neurodevelopmental impairment. We hypothesised that the relationship between maternal birthweight and gestational length would be more evident in twin than in singleton pregnancies, as there is more variation in gestation in the former. Among 131 singleton mothers carrying twins, there was weak evidence of a positive relationship between maternal birthweight and twin gestational length (+0.6 weeks [95% CI −0.05, +1.3] per kg increase in maternal birthweight, but stronger evidence among 56 of these who went into labour spontaneously (+1.9 weeks [+0.7, +3.1], P = 0.003 for interaction). In the latter group we estimated that the odds of very preterm birth (at