A new approach to assessing the effect of birth order on the outcome of pregnancy

Abstract

SummaryA new approach is suggested for assessing the relationship between birth order and pregnancy risk. Population data are used to estimate the risk of a poor pregnancy outcome after different reproductive histories. The risk of a poor outcome at the first pregnancy appears to be twice that at subsequent pregnancies, but no change in risk is observed between the second and fifth birth orders. If there has been a previous poor pregnancy outcome, the risk of another is increased four-fold.