A recent study, published in the journal Neurology assessed foetal risk after pregnancy exposure to natalizumab (Tysabri) in women with multiple sclerosis (MS). The Italian study specifically focused on spontaneous abortion and congenital anomalies.
Data of all pregnancies occurring between 2009 and 2015 in patients with MS treated with natalizumab and referring to 19 participating sites, were collected and compared with those of pregnancies in untreated patients and patients treated with injectable immunomodulatory agents (interferon-β (IFN-β)).
Rates of spontaneous abortion and congenital anomalies were also compared with those reported in the Italian population.
A total of 92 pregnancies were tracked in 83 women. Researchers followed up with these women every six months, when they had a relapse and one year after giving birth. The results showed that exposure to natalizumab during the first three months of pregnancy was associated with a 17.4% risk of miscarriage. A higher risk than women who were untreated or treated with IFN-β. The risk of major birth defects was also higher (3.7%) than those untreated or treated with IFN-β.
However, although the risk of miscarriage and birth defects were higher in women taking natalizumab these statistics were still within the estimates for the general population.
Both natalizumab and IFN-β was associated with lower length and weight of the babies.
Researchers concluded that natalizumab exposure to up 12 weeks of gestation is associated with an increased risk of spontaneous abortion, although within the limits expected in the general population, whereas the risk of congenital anomalies needs further investigation. Taking into account the high risk of disease reactivation after natalizumab suspension, the researchers concluded that pregnancy could be planned continuing natalizumab while strictly monitoring conception.