Women who have had tonsillectomies or appendectomies appear to be more likely to get pregnant and get pregnant earlier, according to a study in the journal Fertility and Sterility. The effect is even more pronounced when women have had both procedures.

That could be because eliminating one or both of these mostly useless but potentially inflammatory organs brings the body’s overall inflammation levels down, increasing health and boosting fertility chances.

While previous studies had shown increased fertility rates among women who had appendectomies, the study authors explained that researchers did not expect tonsil removal would have similar results. Though the two organs are similar in function and propensity for inflammation and removal, the tonsils are nowhere near as close to reproductive organs as the appendix. Researchers had assumed it was the appendix’s proximity to the fallopian tubes and uterus that made its inflammation possibly affect fertility.

The study examined the primary care records of nearly 177,000 women under age 45 who had had appendectomies, tonsillectomies or both between 1987 and 2012 through the U.K.’s Clinical Practice Research Datalink. They then compared surgical and pregnancy rates to another 355,000 women in a comparison group.

The researchers found that within an average of about 15 years after their operations, about 54 percent of women without appendices became pregnant, 53 percent of women without tonsils became pregnant and nearly 60 percent of women who had had both operations became pregnant. Contrarily, only about 43 percent of the women in the comparison group became pregnant within the same average time frame. The time to pregnancy rates of these women followed a similar pattern, with women who had both tonsillectomies and appendectomies showing the shortest time to pregnancy of the women studied.

The researchers said it is possible that the women who had these procedures also happened to be more sexually active and so more likely to get pregnant than the women who did not have these procedures.

But it’s also possible the resulting decreased overall inflammation in the body explains why women who have had these operations are more likely to get pregnant.

"A degree of systemic or uterine inflammation is essential for normal implantation and pregnancy. However, when inflammation becomes too excessive, chronic or consists of specific mediators in high concentration, it might cause degeneration of the embryo and impaired implantation,” the study authors explained.

It is also possible that because the tonsils and the appendix are immune-associated organs, their removal precipitates a decreased or different immune response than in people who have one or both of these organs left. A slightly decreased immune response (without causing more active disease that would make pregnancy less likely) could make pregnancy more likely because the pregnant woman can more easily tolerate the foreign body of a fetus.

Though both operations are still fairly common, the study authors noted that their incidence “has decreased markedly” in recent years. The authors called for more research to tease out the exact mechanisms by which this organ removal-fertility association is possible to provide more information about one factor when deciding for or against appendectomy and/or tonsillectomy.

If nothing else, they pointed out, this study is good evidence to allow surgeons to tell women who need appendectomies and tonsillectomies that there is no increased risk of infertility after these operations.