Reproductive biomedicine in space: implications for gametogenesis, fertility and ethical considerations in the era of commercial spaceflight.

As the era of commercial and frequent spaceflight advances, the question of human fertility in space is no longer theoretical but urgently practical. Despite over 65 years of human spaceflight activities, little is known of the impact of the space environment on the human reproductive systems during long-duration missions. Extended time in space poses potential hazards to the reproductive function of female and male astronauts, including exposure to cosmic radiation, altered gravity, psychological and physical stress, and disruption to circadian rhythm. This review encapsulates current understanding of the effects of spaceflight on reproductive physiology, incorporating findings from animal studies, a recent experiment on sperm motility, and omics-based insights from astronaut physiology. Female reproductive systems appear to be especially vulnerable, with implications for oogenesis and embryonic development in microgravity. Male reproductive function reveals compromised DNA integrity, even when motility appears to be preserved. This review examines the limited embryogenesis studies in space, which show frequent abnormal cell division and impaired development in rodents. Alongside physiological findings, this review explores ethical issues of space work, particularly with increasing spaceflights involving non-professional astronauts and individuals of all ages. This convergence of space medicine, reproductive biology and bioethics represents a novel and critical intersection that warrants attention. Drawing from multidisciplinary fields, a collaborative framework is proposed for future research, aiming to catalyse cross-disciplinary dialogue and guide the next generation of reproductive biomedical research in space.