Optimal weight gain during twin pregnancy in Japanese women with favorable perinatal outcomes.

<bold>Objective: </bold>We examined the optimal weight gain in the healthy Japanese women with favorable perinatal outcomes of (dichorionic) twin pregnancy.<bold>Methods: </bold>We calculated the average weight gain in the women whose height was 150-164 cm with favorable perinatal outcomes of dichorionic twin pregnancy set for this study. The women were categorized to underweight, normal, overweight and obese based on the pre-pregnancy body mass index (BMI) categories according to the Institute of Medicine (IOM) and the World Health Organization (WHO) body mass index (BMI) cutoffs.<bold>Results: </bold>The average GWG in the normal-weight women with the favorable perinatal outcomes was 13.9 ± 3.6 kg. It was significantly different from that in the underweight, overweight and obese women according to the both 2 BMI cutoffs by Student's t-test (p < 0.01).<bold>Conclusion: </bold>There are optimal ranges of weight gain during twin pregnancy based on the BMI classification. [ABSTRACT FROM AUTHOR]