The Editor has retracted this article [1]. Following publication significant concerns regarding the study design and analysis were raised [2]. Post-publication review confirmed a number of these aspects, including inadequate description of the trial design and that potential confounding was not sufficiently accounted for. The results and conclusions are therefore unreliable.

Gideon Koren does not agree to this retraction; Daniella Gilboa and Rachel Katz have not responded to any correspondence about this retraction.

The online version of this article contains the full text of the retracted article as electronic supplementary material.

[1] Koren, G., Gilboa, D. & Katz, R. Fetal Safety of Dydrogesterone Exposure in the First Trimester of Pregnancy. Clin Drug Investig (2019). https://doi.org/10.1007/s40261-019-00862-w

[2] Koren, G., Gilboa, D. & Katz, R. Expression of Concern to: Fetal Safety of Dydrogesterone Exposure in the First Trimester of Pregnancy. Clin Drug Investig (2020). https://doi.org/10.1007/s40261-019-00884-4