Women who have had their appendix or tonsils removed appear to be more fertile, a 15-year study suggests.
The researchers, at the University of Dundee, analysed medical records from more than half a million British women.
They argue the operations could directly affect fertility or there may be a "behavioural" explanation.
Experts said the findings might lead to new treatments, but advised women not to have their tonsils and appendix taken out unnecessarily.
The study found that for every 100 pregnancies in women who had had no procedures there were:
- 134 pregnancies in women who had had their appendix removed - 149 pregnancies in women who had had their tonsils removed - and 143 pregnancies in women who had had both removed
One of the researchers, Dr Sami Shimi, said most doctors were wrongly taught that having an appendix removed damaged fertility.
'Reassuring'
He told BBC News: "This [study] is very important in reassuring young women that appendicectomy will not reduce their chances of future pregnancy.
"More importantly, looking at both the appendix and tonsils together, this study confirms beyond doubt that removal of inflamed organs or organs likely to suffer from repeated inflammation, in women, improves their chances of pregnancy."
Explaining the findings, published in Fertility and Sterility, is more of a challenge.
One biological possibility is that regularly infected tonsils or appendixes raise levels of inflammation in the body, which affects the ovaries and womb.
The Dundee team favour a behavioural explanation such as women enjoying more "liberal sexual activity", being both more likely to get pregnant and have pelvic inflammatory disease, which could lead to an appendix being removed.
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