Second generation follow-up of the Danish perinatal study women: study design and factors affecting response.

To study the mother-infant correlation of fetal growth and duration of pregnancy, women who were born as subjects in the Danish Perinatal Study (1959-61) were traced and interviewed, and the pregnancy and birth records of their children were abstracted. The study population consisted of 159 women who were small-for-gestational age (SGA) at birth, 162 who were preterm, 38 who were both preterm and SGA, and 939 term, appropriately-grown control women. Methods for sample selection, measuring gestational age and fetal growth in both generations, locating and interviewing the women, abstracting the records of their children, and obtaining paternal birth and adult stature are described. A total of 84.5% of the selected women were successfully interviewed; the fraction interviewed did not differ by maternal birth status. The medical records of over 98% of pregnancies to the study women were abstracted, making it possible to study various factors associated with completion of an interview. By a variety of measures, women of higher socio-economic status were more likely to be interviewed. Birthweight and adult weights were available for 63 and 73% of the children's fathers.