Gene mutation likely cause of unexplained female infertility

Scientists have not yet been able to identify the cause of the problem in an estimated 10 to 15 per cent of couples with infertility and 50 per cent of women with recurrent pregnancy loss. 

The findings, conducted in a mice model, showed that women who lacked the gene called Nlrp2 had a spectrum of negative reproductive outcomes including recurrent loss of pregnancies with abnormally developing placentas, loss of the embryo before implantation, or, more rarely, having a baby with developmental disabilities. 

Conversely, when male mice lacked the gene, there was no impact on fertility or offspring, the researchers said, in the paper appearing in the journal Scientific Reports. 

“Women carrying these mutations are healthy in all other physical aspects, so they are unaware that they have these mutations that do not allow them to carry a pregnancy,” said lead author Sangeetha Mahadevan, a postdoctoral fellow at Baylor College of Medicine in Texas, US. 

But, when the females lacking the Nlrp2 gene mated, three different types of outcomes were observed -- some did not get pregnant, others had stillborn pups with abnormalities and a third group of females gave birth to live pups of normal appearance, but fewer per litter. 

Some of the  pups were smaller or larger than expected. In addition, when the researchers attempted to grow the eggs of a female mouse carrying the mutation in the Nlrp2 gene in an artificial environment in the lab, they did not develop. 

“This finding has implications for in vitro fertilisation. It is important to recognise that there will be women who may not be candidates for this procedure because their embryos would likely be unable to grow in culture as a result of the females carrying these mutations in NLRP genes,” Mahadevan noted.