Microgravity May Block Reproduction, Complicating Space Colonization

A study using a clinostat to simulate microgravity found that sperm navigation, fertilization, and embryo development are impaired in mammals (humans, mice, and pigs) under near-zero gravity, with fertilization dropping by about 30% in mice and 15% in pigs and embryos showing developmental delays. Progesterone helped sperm navigate but required unusually high concentrations, and safety concerns remain. These findings highlight gravity’s deep role in reproductive biology and suggest that long-term space settlements face significant fertility challenges, underscoring the need for further research before space colonization can be considered viable.