Current prevalence of and obstetric outcomes in underweight Japanese women

We compared the current prevalence of and obstetric outcomes in underweight Japanese women with data from 16 years ago. We reviewed the obstetric records of singleton pregnant Japanese women who delivered at our institute at ≥ 22 weeks’ gestation from 2000 through 2002 and those from 2016 through 2018. From 2000–2002 to 2016–2018, numbers of pregnant women in their twenties decreased and pregnant women in their forties increased significantly (p < 0.01). There were no significant changes in the prevalence of underweight pregnant women between the 2 periods. The prevalence of women whose weight gain during pregnancy was less than optimal increased (p = 0.049). There was no difference in obstetric outcomes between the 2 periods. Based on the current results, we cannot judge the necessity of further education to curb the increasing trend of Japanese women who desire slimness. Maternal weight may not have a high priority as an indicator of the gestational nutritional status associated with obstetric outcomes in Japan.