Endometriosis linked to reduction in live births before diagnosis of the disease, study finds

Endometriosis may be linked to a reduction in fertility in the years preceding a definitive surgical diagnosis, researchers from Finland have found.

In the first study to look at birth rates in a large group of women who received a surgical verification of endometriosis, scientists discovered that the number of first live births in the period before diagnosis was half that of women without the painful condition, regardless of the form of endometriosis.

The research team also found evidence that the number of babies women had before endometriosis was diagnosed was significantly reduced, compared to women without an endometriosis diagnosis.

“Our findings suggest that doctors who see women suffering from painful menstruation and chronic pelvic pain, should keep in mind the possibility of endometriosis and treat them effectively,” said Professor Oskari Heikinheimo of Helsinki University Hospital, who led the study.

“Doctors should discuss with these women the possible effects on their fertility, in addition to the effects of their age, and the impairment of fertility should be minimised by offering relevant treatment for endometriosis without delay.”

Endometriosis is a chronic inflammatory condition where tissue similar to the lining of the womb grows in other places, such as the ovaries and fallopian tubes, affecting up to about 10 per cent of women of child-bearing age.

Typical symptoms include painful menstruation, pain in the pelvic area, difficult or painful sexual intercourse, and difficulty getting pregnant. Surgery has traditionally been the “gold standard” for diagnosing the condition and classifying the type of endometriosis, although diagnosis by ultrasonographic findings or the symptoms alone is currently accepted.

Until now, there has been little information about the live birth rate among women with endometriosis, and little is known about the possible effects of different types of endometriosis on fertility, especially in the years before a diagnosis.

“Given the chronic nature and typical long delay in diagnosis of endometriosis, we wanted to find out if there were differences in first birth rates before diagnosis in a large group of women in the population,” Professor Heikinheimo explained.

He and his colleagues looked at 18,324 women in Finland, aged between 15 and 49 years, who had surgical verification of endometriosis between 1998 and 2012. They matched them with 35,793 women of similar age who did not have an endometriosis diagnosis.

The follow-up period started at the age of 15 years, and continued until the first live birth, sterilisation, removal of the ovaries or womb, or until the surgical diagnosis of endometriosis, whichever came first.

The group of women with endometriosis were also divided into four groups according to the type of endometriosis.

A total of 7,363 women (40 per cent) with endometriosis and 23,718 women (66 per cent) without endometriosis delivered a live born baby during the follow-up period. The incidence rate of first live births among women with endometriosis was half that of women without the condition.

When analysed according to women’s birth decade from 1940s to 1970s, the birth rate decreased in both groups of women. Importantly, over the decades, an increasingly lower first live birth rate was seen in women with endometriosis, compared to women without.

In those women born in 1940-1949, the difference in live birth rates between the two groups was 28 per cent before surgically diagnosed endometriosis, but this difference increased steadily to 87 per cent by 1970-1979, the study showed.

“We assume that this is associated with the older age of women when they have their first baby, earlier surgical diagnosis of endometriosis and accumulating adverse effects of endometriosis in women affected by the condition,” said Heikinheimo.

“The possible effect of endometriosis on the desired number of children highlights the importance of early diagnosis and treatment of the disease,” he said, noting that the number of children that women had before their diagnosis of endometriosis was 1.93 and 2.16 for women without endometriosis.

“It is important to note that this study reports on live births before a definitive diagnosis of endometriosis,” the researcher added.

“Next, we will be reporting on the fertility rates after the surgical diagnosis and treatment of endometriosis. We hope that the fertility of women with endometriosis catches up with that of the women without the condition after surgical management.”

Although important, the study comes with some limitations. These include its focus on only surgically-confirmed endometriosis, which may have ruled out women with milder symptoms who were treated for the condition.

There were no data available on whether or not women wanted to become pregnant. The researchers could not rule out the possible effect of fertility treatments or the effect of adenomyosis, which is known to occur often with endometriosis, and which also affects fertility and pregnancy outcomes.

Differences in socioeconomic and educational backgrounds between the two groups of women might have also affected the findings, the researchers noted.