The association between parents' unemployment and birthweight in Japan

The association between birthweight and parents' occupations was examined with the 1985 Japanese Vital Statistics, which recorded 1,419,465 live births delivered in Japan from April 1985 through March 1986. The mean birthweights [MBWs] were significantly different according to the paternal occupation as well as the maternal occupation after adjusting for the infants' sex and parity. The MBWs of children of unemployed fathers were significantly lighter than those of offspring of employed fathers. This was due to both retarded intrauterine growth and a shortened gestational period. By contrast, the MBWs were not affected by the unemployment of mothers. The possible reasons for the decreased MBW in the case of unemployed fathers were economical problems due to unemployment, less favorable characteristics of demography and obstetrics, and psycho-social stress among the wives of the unemployed.