Prepregnancy low body mass index is not a predictor of labor complications.

The course of delivery and fetal outcome in 149 women with forecoming normal pregnancy and a prepregnancy body mass index (BMI) less than 20.0 were compared to a similar group of women with BMI between 20.0 and 24.9 after matching for age and parity. None of the women was undernourished. Suspected intrauterine asphyxia was significantly more common in primipara with BMI below 18.0 than in their controls (6/12 vs. 1/12), and there was a trend towards fewer babies weighing at least 4,000 g in the women with low BMI. No other significant differences related to BMI were found. It is concluded, that constitutional low weight for height is not a predictor of complications during delivery, and no special observation of this group is recommended.