We have previously reported a positive correlation between the body mass index (BMI) of mothers and the Kaup index of infants at birth and that this correlation may have a stronger influence on the male infants, born to older mothers. Therefore, in this study, we aimed to clarify the correlation between maternal age and gender of the infants as maternal BMI and the Kaup index of infants from birth till 18 mo of age. This study was conducted from April 2010 to September 2011 in Japan. Public health nurses and registered dietitians interviewed the mothers individually under anonymous conditions, and they transferred the required information from the maternity passbook at the 18-mo health checkup. In male infants, significant positive correlations were demonstrated between maternal BMI at the beginning of pregnancy and the Kaup index of infants in mothers older than 35 y when the infants were at birth, at 4 mo and at 18 mo old. In female infants, there was no correlation between maternal BMI and the Kaup index of infants at birth. However, significant positive correlations were demonstrated between maternal BMI and the Kaup index of infants in mothers in their 20s and older than 35 y old when the infants were 4 and 18 mo old. Women who plan on pregnancy and medical professionals need to know that the maternal physique at the beginning of pregnancy affects the physique of the infants at birth and at 4 mo and 18 mo old by gender of the infants.
Keywords: age; body mass index; infant; mother; physique.