Short interpregnancy intervals, maternal folate levels, and infants born small for gestational age: a preliminary study in a Canadian supplement-using population.

Short interpregnancy intervals (SIPI) have been associated with increased risks for adverse neonatal outcomes including preterm delivery and infants small for gestational age (SGA). It has been suggested that mechanistically, adverse neonatal outcomes after SIPI arise due to insufficient recovery of depleted maternal folate levels prior to the second pregnancy. However, empirical data are lacking regarding physiological folate levels in pregnant women with SIPI and relationships between quantified physiological folate levels and outcomes like SGA. Therefore, we sought to test 2 hypotheses, specifically that compared with controls women with SIPI would: (i) have lower red blood cell folate (RBCF) levels and (ii) be more likely to have SGA infants (defined as <10th percentile). Using data collected in British Columbia, Canada, for a larger study on perinatal psychopathology, we documented supplementation use and compared prenatal RBCF levels and proportion of SGA infants between women with SIPI (second child conceived ≤24 months after previous birth, n = 26) and matched controls (no previous pregnancies, or >24 months between pregnancies, n = 52). There were no significant differences in either mean RBCF levels (Welch's t test, p = 0.7) or proportion of SGA infants (Fisher's exact test, p = 0.7) between women with SIPI and matched controls. We report the first data about RBCF levels in the context of SIPI. If confirmed, our finding of no relationship between these variables in this population suggests that continued folic acid supplementation following an initial pregnancy mitigates folate depletion. We found no relationship between SIPI and SGA.