Splish Splash, Genetic Backlash

by Pregnancy.org Staff

strand of DNAIs making a baby taking longer than expected? Scientists have found that some men have a genetic change which makes them less fertile.

Research from the University of California at Davis shows that some sperm lack a protective protein, beta-defensin. This protein coats the swimmer and helps it to move through the mucus found in the female reproductive tract. It acts kind of like a "Klingon cloaking device," study author Gary Cherr said, "helping sperm attach to the surface and sneak their way to an egg. It also keeps the female immune system from attacking sperm cells."

Studies carried out in people from the US, UK, China, Japan and Africa, found the gene mutation is common around the world. About half of all men carry one copy of the defective gene; while a quarter have two defective copies.

Couples trying to conceive found a big drop in pregnancies if a man had two defective genes. They were 30% less likely to become pregnant in any given month. The defective sperm looks normal under a microscope, but struggles to get through to an egg.

What's on the research horizon? A possible intervention for couples might ultimately be a synthetic form of beta-defensin. The protein would be concentrated and applied as a vaginal cream or gel. Sperm would pick up this defensin coat as they advanced into the cervix.

Future research might lead to both clinical and home infertility tests looking for this mutation. If found, the couple could be treated with a procedure such as "intracytoplasmic sperm injection" or ICSI.

For now, Dr Edward Hollox, co-author of the study suggests that if you've got this gene variant you should allow that "little bit longer" if you're trying to get your partner pregnant. For some, all it takes is that extra bit of time and patience.

About the study: Theodore L. Tollner, Scott A. Venners, Edward J. Hollox, Ashley I. Yudin, Xue Liu, Genfu Tang, Houxun Xing, Robert J. Kays, Tsang Lau, James W. Overstreet, Xiping Xu, Charles L. Bevins, and Gary N. Cherr. A Common Mutation in the Defensin DEFB126 Causes Impaired Sperm Function and Subfertility. Although sperm from men carrying two mutated copies of DEFB126 showed no signs of defect or shape change, they were 84% slower moving through a gel. Couples where the man carried two mutated copies of DEFB126 were 30% less likely to conceive a baby in a given month than couple with at least one normal copy of the gene.

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