of Health (NHLBI, 1998). These categories have been widely adopted in the United States and internationally and, if used in formulating recommendations for GWG, would provide opportunities for a consistent message to women and health care providers about weight status for all groups of adults, including women of childbearing age. For these reasons, the committee adopted the WHO BMI categories for its recommendations.
Evidence from the scientific literature is remarkably clear that pre-pregnant BMI is an independent predictor of many adverse outcomes of pregnancy (see Chapter 5). These data provide ample justification for the choice made in the IOM (1990) report to construct weight-gain guidelines according to prepregnant BMI. That approach has been retained in the current document.
The following discussion summarizes the committee’s decision-making regarding whether any special populations warrant separate guidelines. The committee considered women of short stature, adolescents, women with multiple fetuses, racial or ethnic group, obesity classes II and III, parity, and smokers. Of these, evidence suggests that only women with multiple fetuses warrant modified guidelines.
The IOM (1990) report guidelines recommended that women of short stature (< 157 cm) gain at the lower end of the range for their prepregnant BMI. The committee was unable to identify evidence sufficient to continue to support a modification of GWG guidelines for women of short stature (Vishwanathan et al., 2008). The limited data available to the committee indicated that women of short stature had an increased risk of emergency cesarean delivery but that this risk was not modified by GWG; they did not have an increased risk of having an SGA or LGA infant or of excessive postpartum weight retention compared to taller women (Appendix G). No information was available with which to evaluate whether a modification of guidelines might be necessary for very short (< 150 cm) women.
As discussed in Chapter 4, the committee was unable to identify sufficient evidence to continue to support a modification of the GWG guidelines for adolescents (females < 20 years old) (Vishwanathan et al., 2008) (see Chapter 4). The committee also had to resolve the difference in cutoff values for BMI categories between the growth charts commonly used for adolescents and those used for adults. This is because, for adolescents