In fact, UK researchers found women who'd had their appendix removed were more likely to get pregnant later on than women who hadn't had the common surgery.

Dr. Alan B. Copperman, who heads the division of reproductive endocrinology at Mount Sinai Medical Center in New York and was not involved in the new work, called the results "reassuring."

"We always assume that appendectomy is a risk factor for infertility," he told Reuters Health. "This study showed us it wasn't necessarily the appendectomy that put patients at risk."

Still, he warned, "I would not conclude that your fertility is enhanced by appendectomy."

The procedure is one of the most common surgeries in the U.S. and is usually done to treat appendicitis, a potentially life-threatening inflammation of the appendix.

One in 14 people nationally will have appendicitis at some point in their life. It most commonly occurs in young people age 10 to 30.

Ruptured appendixes and bad pelvic infections after appendectomies are known to increase the risk of infertility. Some reports have also suggested the appendectomy itself might hurt a woman's fertility, presumably because it could leave scar tissue sticking to the fallopian tubes, snagging the egg on its way to the uterus.

"A lot of patients thought they would become infertile after appendicectomy (appendectomy)," said Dr. Sami Shimi, a surgeon at the University of Dundee in Scotland, who worked on the new study. "But when I looked at the reports supporting this, they were really weak."

He and his colleagues decided to do a bigger study, using a limited patient database. They were taken aback by the results.

"I was completely surprised that patients who had had an appendicectomy or appendicitis were more fertile, they had more subsequent pregnancies," Shimi told Reuters Health. "And I thought, OK, I have done something wrong here."

So the team tapped into one of the world's largest digital repositories of medical records from primary care, the General Practice Research Database from the UK.

Out of more than 76,000 women who'd undergone an appendectomy, 39 percent had a first pregnancy in the decade following the procedure, according to results published in the journal Fertility and Sterility.

The rate for twice as many women who hadn't had the surgery was only 28 percent. Although the follow-up time was slightly shorter for this group, the fertility gap remained after accounting for age, birth control use, number of previous hospitalizations and other factors.

But Copperman cautioned against making too much of that finding.

"When you go back and retrospectively look at even really large databases, you wonder whether there are confounding factors or biases that cloud the results," he said.

Shimi and his colleagues are still scratching their heads over the strange finding and are currently working to find out if it's a real biological phenomenon or if there is something unique about women who get appendectomies.

For now, Shimi said, what seems certain is that women shouldn't fret about fertility problems if they need an appendectomy.

"That fear is unfounded," the researcher said.

SOURCE: bit.ly/L2v0eB Fertility and Sterility, online June 7, 2012.

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