Pregnancy outcome after first-trimester exposure to JAK inhibitors - an evaluation of the German Embryotox cohort.
- 1Charité - University Medical Center Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Clinical Pharmacology and Toxicology, Embryotox Center of Clinical Teratology and Drug Safety in Pregnancy, Augustenburger Platz 1, 13353, Berlin, Germany. [email protected].
- 2Charité - University Medical Center Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Clinical Pharmacology and Toxicology, Embryotox Center of Clinical Teratology and Drug Safety in Pregnancy, Augustenburger Platz 1, 13353, Berlin, Germany.
Abstract
Background
Janus kinase inhibitors (JAKi) are increasingly being used in the management of autoimmune diseases across rheumatology, gastroenterology, and dermatology, including in women of childbearing age. Consequently, pregnancies occurring during JAKi treatment are becoming more common. However, uncertainties regarding their safety during pregnancy remain, and current human data are insufficient to allow a comprehensive assessment of fetal risk.Methods
Observational data of pregnancies with first trimester JAKi exposure, recorded in the German Embryotox database, was analyzed. Pregnancies were prospectively enrolled between January 1, 2017, and November 15, 2025. Study endpoints included major congenital anomalies, pregnancy loss, and neonatal parameters.Results
The cohort comprised a total of 44 pregnancies exposed to baricitinib (n = 17), filgotinib (n = 3), tofacitinib (n = 8), or upadacitinib (n = 16). A total of 32 live births were recorded. Among these, two major congenital anomalies were observed, one ventricular septal defect and one hypospadias. Five spontaneous abortions occurred, including one case of fetal anencephaly, and seven elective terminations of pregnancy were reported. Additional neonatal assessments revealed two preterm births at 36 weeks' gestation, three infants born small for gestational age, and two newborns large for gestational age.Conclusions
The current evidence is insufficient to establish or exclude an association between JAK inhibitor exposure and adverse fetal outcomes. To date, the potential for harmful effects cannot be ruled out due to the limited available data. Therefore, routine use of JAKi during pregnancy is not recommended and treatment should be approached with caution, and requires a critical risk-benefit assessment until further data is obtained.Trial registration
The study was retrospectively registered in the German Clinical Trials Register on March 16, 2026 (DRKS00039622).
Related
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BibTeX
@article{habbel2026pregnancy,
title = {{Pregnancy outcome after first-trimester exposure to JAK inhibitors - an evaluation of the German Embryotox cohort.}},
author = {Anna-Sophia Habbel and Evelin Beck and Anne Mueller and Katarina Dathe},
journal = {BMC pharmacology \& toxicology},
year = {2026},
month = oct,
doi = {10.1186/s40360-026-01263-4},
url = {https://europepmc.org/article/MED/42908038},
note = {CC BY},
}
RIS
TY - JOUR
TI - Pregnancy outcome after first-trimester exposure to JAK inhibitors - an evaluation of the German Embryotox cohort.
AU - Anna-Sophia Habbel
AU - Evelin Beck
AU - Anne Mueller
AU - Katarina Dathe
PY - 2026
DA - 2026/10/20
JO - BMC pharmacology & toxicology
DO - 10.1186/s40360-026-01263-4
UR - https://europepmc.org/article/MED/42908038
AB - Background Janus kinase inhibitors (JAKi) are increasingly being used in the management of autoimmune diseases across rheumatology, gastroenterology, and dermatology, including in women of childbearing age. Consequently, pregnancies occurring during JAKi treatment are becoming more common. However, uncertainties regarding their safety during pregnancy remain, and current human data are insufficient to allow a comprehensive assessment of fetal risk.Methods Observational data of pregnancies with first trimester JAKi exposure, recorded in the German Embryotox database, was analyzed. Pregnancies were prospectively enrolled between January 1, 2017, and November 15, 2025. Study endpoints included major congenital anomalies, pregnancy loss, and neonatal parameters.Results The cohort comprised a total of 44 pregnancies exposed to baricitinib (n = 17), filgotinib (n = 3), tofacitinib (n = 8), or upadacitinib (n = 16). A total of 32 live births were recorded. Among these, two major congenital anomalies were observed, one ventricular septal defect and one hypospadias. Five spontaneous abortions occurred, including one case of fetal anencephaly, and seven elective terminations of pregnancy were reported. Additional neonatal assessments revealed two preterm births at 36 weeks' gestation, three infants born small for gestational age, and two newborns large for gestational age.Conclusions The current evidence is insufficient to establish or exclude an association between JAK inhibitor exposure and adverse fetal outcomes. To date, the potential for harmful effects cannot be ruled out due to the limited available data. Therefore, routine use of JAKi during pregnancy is not recommended and treatment should be approached with caution, and requires a critical risk-benefit assessment until further data is obtained.Trial registration The study was retrospectively registered in the German Clinical Trials Register on March 16, 2026 (DRKS00039622).
SN - 2050-6511
ER -