Short interpregnancy intervals and unfavourable pregnancy outcome: role offolate depletion

There is no generally accepted explanation for the excess risk of adverse p regnancy outcome after short interpregnancy intervals. In this paper, we pr esent a hypothesis that is both biologically plausible, empirically testabl e, and able to explain many observations. Maternal serum and erythrocyte co ncentrations of folate decrease from the fifth month of pregnancy onwards a nd remain low for a fairly long time after delivery. Women who become pregn ant before folate restoration is complete have a raised risk of folate insu fficiency at the time of conception and during pregnancy. As a consequence, their offspring have higher risks of neural tube defects, intrauterine gro wth retardation, and preterm birth. We make several predictions based on ou r hypothesis and suggest ways of testing them empirically. The proposed mec hanism implies, among other things, that postpartum supplementation with fo lic acid might prevent excess risk of unfavourable pregnancy outcome in wom en with short interpregnancy intervals.