Swedish researchers, say the practice of female circumcision, which is practised in more than 30 countries and affects 2 million girls each year, could cause infertility.
The researchers examined nearly 300 women in Sudan where the practice is widespread, and say that women who had undergone circumcision, or female genital mutilation (FGM), were five to six times more likely to be infertile.
Dr Lars Almroth, a paediatrician and researcher at the Karolinska Institute in Stockholm, said that all female circumcision, and not only the severe forms, probably cause an increased risk of infertility, and this is a very important argument to be used in areas where this is practised.
Human rights campaigners have rightly described the practice as an atrocity against womanhood; female circumcision is practised in Africa and is common in some countries in the Middle East despite vigorous campaigns to stop it.
The practice involves the removal of part or all of the female genitalia.
According to the human rights group Amnesty International, an estimated 135 million women and girls have been circumcised.
It is often considered part of the culture, a tradition or a rite of passage to adulthood, and in some countries it is viewed as a means of reducing a woman's sexual desire and of safeguarding her fertility.
This new research is the first clinical study to show it has the opposite effect.
Almroth says they found that the more extensive form of genital mutilation, the higher the risk of primary infertility, and the risk is 5 to 6 times higher than in women who had not been not circumcised.
According to Almroth and his colleagues infertility may be caused by infection, inflammation, scarring or by the physical alterations resulting from the circumcision.
Almroth says in Sudan up to 90 percent of women have had some form of genital mutilation.
The average age of circumcision for women in the study was 7, but it is performed on girls as young as 4.
Crude instruments are often used in some countries to perform the circumcision, and nothing is given to relieve the girl's pain.
In their study the researchers examined 99 infertile women and 180 others who were pregnant for the first time, from two hospitals in Khartoum.
They controlled for other factors that could cause infertility, such as sexually transmitted infections, age and social and economic conditions.
Almroth says female circumcision was the only factor that stood out.
The study is published in The Lancet.