Elevated cord levels of ustekinumab following its use in the treatment of Crohn's disease in pregnancy.

Ustekinumab (USK) was used in the treatment of two pregnant patients with Crohn's disease. It was given in the third trimester and restarted postnatally for both women. One woman remained on USK and in remission throughout pregnancy. The second woman, took a treatment break, flared, and then had remission induced with reintroduction of USK. Both women delivered healthy term infants. The interval from last dose to birth was 11 and 8 weeks respectively. Interestingly, USK levels in cord blood was observed in higher concentrations than in the maternal serum taken in third trimester. While no adverse effect in infants has been observed, clinicians should remain aware of fetal transfer when using USK in pregnancy. An evaluation of risk and benefit may favour continuing USK in pregnancy in patients with refractory disease.