Biology: Microgravity hinders egg fertilisation and early embryo development (Communications Biology)

Sperm cell navigation, egg cell fertilisation, and early embryo development are negatively affected by simulated low gravity (microgravity) conditions, according to a study involving human, mice and pig cells published in Communications Biology. The findings highlight some of the potential challenges around mammalian reproduction in microgravity.

Crewed missions to the Moon and Mars — both low gravity environments — are planned within the next decade. Microgravity has previously been shown to affect male sex-hormone levels in humans and stem cell specialisation in mice, but its effects on sex cell behaviour and early embryo development remain unclear.

Nicole McPherson and colleagues compared the behaviour of sperm cells from humans, mice, and pigs under simulated microgravity — generated using a continuously rotating device known as a Clinostat — and standard Earth gravity as they moved through a narrow channel designed to model the cervix. The authors found that significantly fewer human sperm were able to navigate the channel under microgravity conditions, compared to standard Earth gravity, although their overall movement strength was similar in both conditions. However, when 100 micromolar of progesterone — a hormone emitted by developing eggs that can aid sperm navigation and that is typically present at 10 micromolar — was introduced to the system, sperm performance was partially restored to levels seen under standard Earth gravity. Mice and pig sperm were also less able to navigate the channel under simulated microgravity, although pig sperm movement efficiency was not affected.

When the authors compared egg fertilisation success and embryo development in mice and pig cells, they found that 30% fewer mouse eggs were successfully fertilised after four hours exposure to microgravity, compared to the same experiments under standard Earth gravity. Additionally, fewer pig embryos reached the blastocyst stage of development after four hours of microgravity exposure, compared to standard Earth gravity.

Together, the findings suggest that while mammalian reproductive processes can occur under simulated microgravity, they are negatively affected by these conditions. The authors note that it remains unclear whether embryos fertilised and developed entirely in microgravity can give rise to sustained pregnancies, and suggest future research should assess the long-term reproductive sustainability of humans and animals in space.

• Article
• Open access
• Published: 26 March 2026

Lyons, H.E., Nikitaras, V., Arman, B.M. et al. Simulated microgravity alters sperm navigation, fertilization and embryo development in mammals. Commun Biol 9, 401 (2026). https://doi.org/10.1038/s42003-026-09734-4

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