While obesity during pregnancy is associated with several complications, the relation between maternal pre-pregnancy and the risk of preterm birth is not well-established. This study aims to examine the association between pre-pregnancy obesity and subsequent risk of preterm birth.

This population-based cohort study included a total of 7,141,630 singleton live births, including 527,637 (7.4%) preterm births. Mothers who had live singleton birth and did not have pre-existing diabetes or hypertension were included. The pre-pregnancy BMI of the mothers was considered to define pre-pregnancy obesity. The primary outcome of the study was preterm birth associated with the risk of pre-pregnancy obesity.

The findings suggested that pre-pregnancy obesity in mothers was significantly associated with the risk of preterm birth, as compared with mothers without pre-pregnancy obesity. In some women aged 20 or younger, pre-pregnancy obesity was associated with a lower risk of preterm birth, though the data available was not significant enough to establish this relation. The same trends of lower risk of preterm birth were also reported in some women aged 30 or younger with pre-pregnancy obesity.

The research concluded that maternal pre-pregnancy was associated with an increased risk of preterm birth in the general population of women. However, the risk can vary in different women.

Ref: https://www.thelancet.com/journals/landia/article/PIIS2213-8587(19)30193-7/fulltext