Testosterone may protect against the harmful effects of inflammation and increase male embryo survival in mice, reports a paper published online this week in Nature. The protective effects of testosterone were replicated by administering ibuprofen to pregnant mice, although this does not mean that ibuprofen could protect embryos in human pregnancies.

During pregnancy, inflammation responses are usually repressed to prevent harm to the fetus. Although it is established that chronic DNA damage during embryo development can lead to inflammation, little is known about the consequences of maternal or fetal inflammation during pregnancy.

John Schimenti and colleagues investigated the survival rates of mouse embryos with a mutated genotype that caused defective DNA replication and repair during embryo development. This process subsequently led to DNA damage and inflammation. The authors observed that female mouse embryos were much less likely to survive than male mouse embryos in this scenario. This survival bias was probably due to the presence in male embryos of testosterone, which has a protective, anti-inflammatory effect. When pregnant mice were administered with testosterone, the survival of female embryos increased markedly.

The authors additionally report that the administration of ibuprofen, a non-steroidal anti-inflammatory drug (NSAID), to pregnant mice also ensured equal survival rates of male and female embryos. Further research will be needed to investigate the specific causes of inflammation, and to establish whether these findings could be applied to humans.