Who is at risk of inadequate weight gain during pregnancy? Analysis by occupational status among 15,020 deliveries in a regional hospital in Japan

A lower bodyweight may be associated with adverse birth outcomes, such as low birth weight and being small for a given gestational age. In Japan, the rate of low birth weight has been increasing over the last two decades, such that both low pre-pregnancy weight and inadequate weight gain during pregnancy are viewed as critical issues in terms of the reproductive health of Japanese women. The aim of our study was to evaluate the relationship between socioeconomic status (SES) and inadequate weight gain during pregnancy. A cross-sectional, hospitalbased study using data from a large hospital in Hamamatsu city, Japan, from 1997 to 2010 was conducted. Among a total of 21,855 deliveries, 15,020 participants were analyzed. Odds ratios and confidence intervals were estimated using a logistic regression model. We defined maternal occupational status as follows: home-maker married to a salaried-spouse, home-maker married to a self-employed spouse, home-maker married to a professional, all other home-makers, office worker, professional, and all other occupations. In the high SES groups (home-makers married to self-employed spouse and professional spouse, as well as office workers and professional workers), we found an association with inadequate weight gain during pregnancy, especially among underweight women. There was no association between SES and inadequate weight gain among normal-weight and overweight women. Japanese women from higher socioeconomic backgrounds appear to be at greater risk for inadequate weight gain. This result may contribute to enhancing prenatal education on pregnancy-related weight gain in Japan.