Perinatal mortality and mother's marital status at birth in subsequent siblings

The effect of marital status on perinatal mortality is studied for births in Norway, 1967-1981, in terms of relative risk (RR) of unmarried vs. married mothers. The births were linked in units of sibships. At first birth, RR decreased from 1.86 in 1967-1971 to 1.32 in 1977-1981. At second birth the perinatal mortality varied greatly according to marital history with a RR of 2.03 when comparing sibships where mothers were unmarried at both pregnancies with mothers married at both pregnancies. Almost no excess risk was demonstrated for mothers that were married at second birth, but unmarried at first. These mothers appeared to have no excess risk even at the first birth in spite of being unmarried. The results suggest that marital status is still a risk factor to be considered, even in the Scandinavian countries where the marginal effect of marital status in recent years has been reported to be low. To an increasing extent, the high risk women, previously identified by marital status, are now hidden in a larger low risk group which apparently has more stable family relations, e.g. tending to be married at second birth.