For the first half of this century, most medical authorities recommended that weight gain during pregnancy is limited to less than 20 Ib (9·1 kg). Higher weight gains were believed to increase the risks of maternal toxaemia, fetal macrosomia, and operative deliveries. However, by the 1970s, women were being encouraged to gain at least 25 Ib (11·4 kg) because insufficient weight gain could contribute to premature births and to low birthweight term infants. In 1990, an influential report from the US Institute of Medicine recommended a weight gain of 25–35 Ib (11·4–15·9 kg) for women of normal pre-pregnancy weight-for-height; higher and lower gains were recommended respectively for those underweight and overweight before conception (table).
Diet and nutrition