The contribution of circadian, sleep and hormonal rhythms to pregnancy outcomes: an opportunity for improved management of women during pregnancy

Abstract Circadian rhythms are fundamental regulators of physiology and play a critical role in reproductive success. During pregnancy, precise temporal coordination of endocrine, metabolic, and immune processes is required to support maternal adaptation, placental function, and foetal development. Disruption of circadian rhythms through environmental factors such as light at night, shift work, or sleep disorders has emerged as a significant risk factor for adverse pregnancy outcomes, including preterm birth, gestational diabetes, and preeclampsia. In this review, we synthesize current evidence linking circadian and sleep disruption to pregnancy complications, with a particular focus on the temporal regulation of key hormones, including progesterone, oestrogen, cortisol, oxytocin, and melatonin. We discuss how altered rhythmicity of hormone production and tissue responsiveness may impair target tissue function, maternal cardiovascular adaptation, and the development of gestational diabetes. We highlight emerging mechanistic insights into molecular clock regulation across reproductive tissues and its interaction with environmental cues. Finally, we outline opportunities for clinical translation, including chronobiology-informed diagnostics and chronotherapeutic strategies, to improve pregnancy management and reduce the burden of adverse outcomes.