Background: Continuation of biologics for inflammatory disorders during pregnancy is still a difficult decision. Many women with inflammatory bowel diseases (IBDs) stop anti-tumor necrosis factor (anti-TNF) treatment after 24 weeks.

Objective: To evaluate the benefits and risks of anti-TNF continuation after 24 weeks of pregnancy for mothers with IBD and their offspring.

Design: Target trial emulation between 2010 and 2020.

Setting: Nationwide population-based study using the Système National des Données de Santé.

Patients: All pregnancies with birth exposed to anti-TNF between conception and 24 weeks of pregnancy in women with IBD.

Intervention: Continuation of anti-TNF after 24 weeks of pregnancy.

Measurements: Occurrence of maternal IBD relapse up to 6 months after pregnancy, adverse pregnancy outcomes, and serious infections in the offspring during the first 5 years of life was compared according to anti-TNF continuation after 24 weeks of pregnancy using inverse probability-weighted marginal models.

Results: A total of 5293 pregnancies were included; among them, anti-TNF treatment was discontinued before 24 weeks for 2890 and continued beyond 24 weeks for 2403. Continuation of anti-TNF was associated with decreased frequencies of maternal IBD relapse (35.8% vs. 39.0%; adjusted risk ratio [aRR], 0.93 [95% CI, 0.86 to 0.99]) and prematurity (7.6% vs. 8.9%; aRR, 0.82 [CI, 0.68 to 0.99]). No difference according to anti-TNF continuation was found regarding stillbirths (0.4% vs. 0.2%; aRR, 2.16 [CI, 0.64 to 7.81]), small weight for gestational age births (13.1% vs. 12.9%; aRR, 1.01 [CI, 0.88 to 1.17]), and serious infections in the offspring (54.2 vs. 50.2 per 1000 person-years; adjusted hazard ratio, 1.08 [CI, 0.94 to 1.25]).

Limitation: Algorithms rather than clinical data were used to identify patients with IBD, pregnancies, and serious infections.

Conclusion: Continuation of anti-TNF after 24 weeks of pregnancy appears beneficial regarding IBD activity and prematurity, while not affecting neonatal outcomes and serious infections in the offspring.

Primary funding source: None.