Using data from the compulsory Medical Birth Registry of Norway, the authors investigated the effect of maternal multiple sclerosis (MS) on pregnancy, delivery, and birth outcome in 649 births by MS mothers and 2.1 million control births. The mothers with MS had a higher proportion of neonates small for gestational age and also more frequent induction and operative interventions during delivery.

To investigate the influence of maternal multiple sclerosis (MS) on pregnancy, we compared pregnancy, delivery and birth outcome in births prior to onset of MS (pre MS), between MS onset and diagnosis (early MS), and after diagnosis of MS (manifest MS). Mothers with MS were identified through linkage of the Norwegian MS Registry and the Medical Birth Registry of Norway (1967-2002). All pre MS births (n = 1910), early MS births (n = 555), and manifest MS births (n = 308) were compared. There was a significantly lower mean birth weight in term births (adjusted for gestation in weeks, mother's age, time period and caesarean section) in the manifest MS compared to the pre MS group (P = 0.046). The rate of birth complications and interventions did not differ between the three groups. Manifest MS in birth-giving mothers seems to affect birth weight.

Maternal MS affects the birth process and the neonate prenatally, even when the births with planned caesarean section are excluded. MS-related neuronal dysfunction linked to the uterus, is postulated as the most likely mechanism.