Background In the literature it is well known that acitretin is highly teratogen when used in pregnant women. Therefore, several restrictions to all fertile women prior, during and up to three years after ended treatment are recommended. However, as for paternal acitretin exposure data is very limited leading to worries and anxiety among couples planning or already pregnant.

Methods We conducted a nationwide cohort study during the period between 1996–2016 investigating paternal acitretin exposure and the risk of spontaneous abortions and the association to major malformation. Data were obtained from the Medical Birth Registry and the National Hospital Registry. All fathers exposed to acitretin were identified by the Danish National Prescription Registry.

Results We identified in total 1.477.252 registered pregnancies with known father identity. Of these 244 pregnancies and 205 children were exposed to paternal acitretin treatment between one year prior to conception to the end of first trimester. The adjusted hazard risk (HR) of spontaneous abortion was 0.71 (95% CI: 0.43–1.17). When analysing exposure three months prior to conception and during first trimester only, the adjusted HR was 0.76 (95% CI:0.38–1.51) and 1.06 (95% CI:0.55–2.04), respectively. As for the association between major malformation and paternal acitretin exposure between one year prior to conception to the end of first trimester the adjusted odds ratio (OR) was 1.15 (95% CI: 0.57–2.34). When stratifying for the period of acitretin exposure the same insignificant trend was detected. In addition, both spontaneous abortions and major malformation were independent of dosage.

Conclusion We found no increased risk of spontaneous abortions or major malformation in pregnancies exposed to paternal acitretin one year before to three months after conception. This was persistent when sub-analysing exposure period and dosage. These data are an important contribute to the sparse evidence suggesting that paternal acitretin exposure during fertility is safe.

Disclosure(s) Nothing to disclose