Low birthweight and prematurity in relation to paternal factors: a study of recurrence

Background The importance of paternal determinants in the occurrence of low birthweight and prematurity is not well known. We investigated these outco mes in siblings and paternal half siblings as a function of changes in puta tive external determinants between two births in fathers who had experience d the birth of a premature and/or low birthweight (PTB/LBW) infant. Methods All fathers who, between 1980 and 1992, had an infant born before 3 7 completed weeks' gestation or weighing <2500 g and a following child were studied. We identified 14 147 pairs of siblings from Danish national regis ters. The recurrence risk was studied in three sub-cohorts defined by the o utcome in the index child (PTB only, PTB/LBW, LBW only). We estimated the r ecurrence risk in the younger sibling according to changes of female partne r, municipality type, occupation, and father's social status. Results The overall recurrence risk was 16.7% for preterm delivery and 16.8 % for LBW. Changing female partner was, as expected, associated with a redu ction in the recurrence risk for both outcomes (RR = 0.40; 95% CI : 0.27-0. 60 for preterm delivery and RR = 0.38; 95% CI : 0.26-0.56 for LBW). None of the other studied factors was associated with changes in the recurrence ri sk. Fathers who changed partner had offspring with similar birthweight and gestational length between the three sub-cohorts, while a difference was ev ident in offspring to fathers whose female partner was unchanged. Conclusions We did not identify any paternal factor of importance in the oc currence of LBW and preterm delivery.