i.e., adverse health outcomes to the mother, can arise in the prenatal and/or postpartum periods. Among the well-studied prenatal maternal outcomes that result from excessive GWG are pregnancy-associated hypertension (including preeclampsia and eclampsia) and risk of complications in labor and delivery. In the postpartum period, weight retention can lead to higher weight status in subsequent pregnancies as well as weight retention and other long-term maternal health consequences such as increased risk for type 2 diabetes and cardiovascular disease. Unfortunately the literature in this area does not allow inference of causality because it is based solely on observational studies.

The committee’s conceptual framework (see Chapter 1) illustrates a model for maternal and child outcomes consequent to GWG outside the ranges recommended by the IOM (1990) report (Figure 5-1). There are numerous potential causal factors, including environmental factors that can influence the determinants of GWG and its consequences, and others that may affect those consequences by other routes. These consequences, i.e., adverse health outcomes to the mother, can arise in the prenatal and/or postpartum periods. Among the most-studied prenatal maternal outcomes resulting from excessive GWG are pregnancy-associated hypertension (including preeclampsia and eclampsia) and the risk of complications in labor and delivery. In the postpartum period, potential consequences include weight retention and lactation performance. Weight retention can lead to higher weight status in subsequent pregnancies predisposing the woman to more adverse reproductive outcomes (creating a cycle of risk) and other long-term maternal health consequences such as increased risk for type 2 diabetes, cancer, cardiovascular disease, and mental health issues. Therefore these outcomes are also included in the model. Unfortunately the literature in this area does not allow inference of causality since it is based solely on observational studies, thus we can not say that gestational weight gain causes these outcomes but rather that it is associated with them. The committee has made inferences using the best data available in consideration of plausible biologic mechanisms, confounding and other aspects of the individual study methodology, and the patterns of results.

CONSEQUENCES DURING PREGNANCY

The committee’s evaluation of the evidence on associations between GWG and consequences for the mother during pregnancy showed that evidence for an association between GWG and pregnancy complications such as GDM and gestational hypertensive disorders is inconclusive because of inconsistent results and methodological flaws. The outcome of mental health during pregnancy is understudied.



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