NEW YORK, Apr 27 (Reuters Health) - A variation in the size of a gene expressed in the lining of the womb could be the cause of infertility in some women, UK researchers reported on Thursday.

The gene is called MUC1, and it appears to play a key role in the attachment and implantation of an embryo in the uterus. If the embryo fails to attach correctly, the pregnancy will fail.

Researchers at the Imperial College School of Medicine in London, UK, found that a group of women with unexplained fertility had MUC1 genes about 75% of the length of the MUC1 gene in women who had successful pregnancies.

The findings are published in the April 28th issue of The Lancet.

"Attachment and implantation [of an embryo] is a complex process involving many different genes working together to ensure a successful pregnancy," Dr. El-Nasir Lalani, one of the authors in the study, told Reuters Health. "There can be no doubt that major future advances in the treatment of infertility will emanate from a better understanding of the molecules controlling implantation."

Lalani and colleagues looked at the size of the MUC1 gene in 10 women who had a history of unexplained infertility and 10 women who delivered at least two children. The infertile women had MUC1 genes that were an average of 2,500 DNA base pairs long, compared with 3,400 units long in the fertile women.

The MUC1 gene makes a protein called MUC1 mucin that extends into the womb. The protein "is probably the first molecule that the embryo encounters on attachment," according to the report.

Lalani said that the extra DNA seen in the gene in fertile women might lead to more effective implantation of the embryo.

The researchers stress that their results are preliminary and that further research will be necessary to determine what exactly MUC1 mucin does in the womb. John White, a co-investigator in the study, is optimistic that further investigation is likely to "help us develop biological strategies to enhance embryo implantation and successful pregnancies."

From ReutersHealth