Thiopurine Exposure During Pregnancy is Not Associated With Anemia in Infants Born to Mothers With IBD

Thiopurines are commonly used to treat inflammatory bowel disease (IBD). Thiopurines are considered safe throughout pregnancy. However, a published study suggested the risk of neonatal anemia was increased if exposed to thiopurines in utero. This prospective cohort study aimed to determine if there is an increased risk of cytopenia among infants born to pregnant people with IBD, exposed or unexposed to thiopurines, compared to infants born to those without IBD.

Pregnant IBD patients, with and without thiopurine exposure, and one cohort of control individuals were recruited over a 5-year period. Consenting individuals completed a questionnaire and infants had a complete blood cell count at the newborn heel prick. Anemia was defined as hemoglobin (Hb) < 140g/L. Descriptive statistics were used to characterize the study population. Fisher exact tests were used to examine differences in outcomes between groups, a P-value of < 0.05 was deemed significant.

Three cohorts were recruited: 19 IBD patients on thiopurines, 50 IBD patients not on thiopurines, and 37 controls (total of 106). Neonatal median Hb was not different with 177g/L (IQR 38g/L) for the IBD thiopurine group, 180.5g/L (IQR 40g/L) for the IBD non-thiopurine group, and 181g/L (IQR 37g/L) for the controls. Nineteen infants (18%) were cytopenic with 12 (11%) anemic, 6 (5.6%) thrombocytopenic, and 1 (0.94%) lymphopenic. Thiopurine exposure was only in one, mildly anemic, infant.

These findings further support physicians and IBD patients contemplating pregnancy that current guidelines recommending thiopurine adherence do not lead to increased perinatal risk of anemia or cytopenia.