Ofatumumab is not approved for use during pregnancy, with current recommendations stating that effective contraception be used up to 6-months before conception. Offspring are potentially at risk of B-cell depletion, reduced immunity and the consequence of delaying vaccination with live vaccines.

11 pregnancies with median exposure duration of 15 days after LMP (Range: -94 to 47days) were inlcuded. 18.2%(2/11) were exposed in the 4-weeks prior to LMP and 72.7%(8/11) after LMP.

Neither B-cell depletion nor lymphopenia were detected with median B-cell counts of 700/μl(Range: 588/μl -2589/μl) and median absolute B-cell counts of 14%(5%-33.3%), as the percentage of lymphocytes. 72.7%(8/11) had umbilical cord blood analysed while 27.2%(3/11) of children had blood taken within 43 days postpartum. 30%(3/10) of children had an infection within the first 6-months postpartum including: covid-19, respiratory syncytial virus and a urinary tract infection. 30%(3/10) of children received the rotavirus attenuated live vaccine at a median of 58 days postpartum (Range: 56-71). One child (33.3%) developed respiratory syncytial virus post vaccination. For one child, no postpartum follow-up was available.

Neither B-cell depletion nor reduction was detected in our cohort of neonates among women exposed to ofatumumab in pregnancy or within the 6-months prior. Our data adds to the growing base of B-cell counts of neonates exposed to anti-CD20 therapy during early pregnancy with generally healthy newborns, not at increased risk of infection and without the need to postpone vaccination