Maternal weight gain ranges for optimal fetal growth in Japanese women.

OBJECTIVE: To identify adequate weight gain ranges during pregnancy in Japanese women. METHOD: Obstetric records from 2001 to 2002 for 46,659 term, singleton, vaginally delivered live births was used to estimate IUGR and macrosomia risk. Total maternal weight gain was grouped according to gestational age-specific percentile values of weight gain as follows: "very low" (under the 25th), "low" (25th to 49th), "moderate" (50th to 74th), "high" (75th to 89th), and "very high" (90th and over). RESULTS: About 6% of infants were identified as having IUGR and 0.9% as macrosomia. IUGR risk was elevated with low weight gains. Macrosomia risk was related to high weight gains and previous spontaneous abortions. CONCLUSION: Achieving weight gains between the 50th and 75th percentiles for gestational age was considered adequate for optimal fetal growth in Japanese pregnant women.