Pregnancy weight gain from 1960s to 2000 in Finland.

OBJECTIVE: To study secular trends in average pregnancy weight gain between the 1960s and 2000 in Finland, and whether the changes were related to body mass index (BMI), age or parity.
DESIGN: Three cross-sectional population surveys in Finland from three different periods.
SUBJECTS: Women who were pregnant in Helsinki in the period 1954-1963 (N=2262), or in Tampere in the period 1985-1986 (N=1771) or in 2000-2001 (N=371). MEASUREMENTS: Pregnancy weight gain was determined from self-reported prepregnancy weight and measured weights during pregnancy.
RESULTS: The mean age and prepregnancy BMI of all pregnant women increased between the 1960s and 2000 (from 26.5 to 29.6 y, from 21.9 to 23.7 kg/m(2)). The mean pregnancy weight gain, adjusted for mother's age, BMI and parity, increased from the 1960s to the mid-1980s from 13.2 to 14.3 kg. The increase was observed in all BMI categories. Compared to the 1960 cohort, the proportion of women with a pregnancy weight gain of less than 10 kg decreased and the proportion of women with a weight gain of 15 kg or more increased in the 1980 cohort. After the mid-1980s, the average pregnancy weight gain remained the same. In all cohorts, overweight women gained least weight during pregnancy, but age and parity were not associated with BMI and parity-/age-adjusted pregnancy weight gain. Higher pregnancy weight gain was associated with higher mean child's birthweight and higher proportion of high birthweight babies in all cohorts.
CONCLUSIONS: The mean pregnancy weight gain has increased since the 1960s, which may be of importance with regard to the development of later obesity. Factors other than changes in prepregnancy BMI, age and parity must explain the increased pregnancy weight gain over time.