Women expected to give birth in 1966 in the provinces of Oulu and Lapland were invited to participate in the Northern Finland Birth Cohort of 1966 (NFBC1966). Data were collected in pre-natal clinics and at birth (e.g. birth weight, length, n = 12,058 live births) [27],[28]. Details of the measurement protocols are published elsewhere [27],[29]. Additional data were collected via health clinics at age 1 y (n = 10,821), postal questionnaire at 14 y (n = 11,010) and 31 y (n = 8,690), and further data on postnatal growth were obtained from communal health clinics.
