Nutritional stress of reproduction - A cohort study over two consecutive pregnancies

Background. The evaluation of nutritional stresses of reproduction is far more complex than perceived in the literature so far. The use of inappropriate outcome measures, the lack of adjustment for the complex inter-relationships among confounding variables, and the poverty of analytical models, has led to conflicting results. Our objective was to evaluate, using a new analytical framework, the maternal and fetal effects of the nutritional stress imposed by reproduction in a cohort of 278 women followed over two consecutive pregnancies. Methods. The analytical framework evaluated nutritional stress over successive pregnancies. The effect of birth interval on change in maternal weight, body mass index and hemoglobin over two consecutive pregnancies was evaluated using multiple linear regression accounting for the effects of maternal age, parity and weight or body mass index or hemoglobin in the first of the two pregnancies. For change in fetal birth weight correction was made for the confounding effect of maternal age, parity and weight, and fetal gestational age, sex and birth weight. Results. Birth interval was associated with change in maternal weight (p=0.001); change in body mass index (p=0.002); and change in birth weight (p=0.048). No association was found between birth interval and change in hemoglobin. Conclusions. The nutritional stress imposed by reproduction affects maternal and fetal outcomes. Maternal nutrient stores can be depleted and fetal growth can be restricted in association with shorter birth intervals. Perinatal nutrition may be improved by adequate spacing of pregnancies with appropriate birth control.