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RNA, or ribonucleic acid, is a molecule used by the body to help code, decode and produce genetic information. Recent research has shown that sperm cells harbor a surprisingly rich amount of RNA, which appears to play a distinct role in fertilization and early development of the embryo, the study authors said.
The researchers then turned to 96 couples who seemed completely healthy but had been unable to conceive. The investigators performed an RNA analysis of the men's sperm, and then provided a series of increasingly invasive fertility treatments for the couple.
Most infertile men did not carry a complete set of sperm RNA elements, the researchers found, and lacking some RNA elements reduced the success rate of natural pregnancy from 73 percent to 27 percent. The greater the number of RNA elements missing from the sperm cell, the lower the likelihood of conception, the researchers said.
However, that didn't mean these couples could not conceive, Krawetz said -- just that they would need more medical assistance.
"When we took those same individuals and went to assisted reproductive technologies, their rate of fertilization and live birth approached that of the group that was successful by the relatively non-invasive techniques," he said.
Dr. Rebecca Sokol, president of the American Society for Reproductive Medicine, praised the researchers' efforts to figure out a man's contribution to conception.
"As a specialist in male reproduction, I think I can say the field of male infertility is in desperate need of a biomarker like this," said Sokol, a professor of obstetrics and gynecology at the University of Southern California Keck School of Medicine. "As far as the field of infertility is concerned, not enough focus is put on the male."
But the results of this preliminary research need to be reproduced, Sokol said. The trial was small, involved a select group of patients, and did not include a truly random control group, she said.
"It's not perfect," she said. "Nothing's perfect. But it's a good first step."
Krawetz hopes that RNA analysis ultimately will prove a useful early test in fertility treatment. Sokol noted that such analysis is time-consuming and potentially expensive, but she could not put a price tag on the procedure.