Women with endometriosis are less likely to conceive and they are also at a greater risk of recurrent pregnancy losses, according to a study of more than 30,000 Danish women published in the January 2023 issue of the journal Fertility and Sterility.¹

A team of Danish researchers collaborated on this research to investigate the association of endometriosis with pregnancy loss and recurrent pregnancy loss. Data for the study was obtained from the National health registers in Denmark. A total of 29,563 women who were diagnosed with endometriosis between 1977 and 2017 were enrolled in this study. 295,630 age-matched women without endometriosis were selected as controls.

More women with endometriosis (14.1%) used assisted reproductive technology to conceive compared to 4.4% of women who did not have endometriosis. Around 20% of women with endometriosis had never been pregnant when compared to 17.5% women without endometriosis.

Nearly 19% of ever-pregnant women with endometriosis had one pregnancy loss, defined as the spontaneous demise of a pregnancy until 22 weeks of gestation compared to 17.3% women who did not have endometriosis with odds ratio of 1.13. More women with endometriosis had greater odds of suffering a greater number of pregnancy losses with 3.9% vs 3.5% experiencing two pregnancy losses with OR of 1.18 and 2.1% vs 1.5% experiencing ≥3 pregnancy losses with OR of 1.44. When adjusted for gravidity, women who had endometriosis had higher odds of suffering 1, 2 and ≥3 pregnancy losses with adjusted ORs of 1.37, 1.75 and 2.57, respectively.

Compared to women without endometriosis, those who had endometriosis were more likely to have primary recurrent pregnancy loss defined as ≥3 pregnancy losses with no history of previous stillbirth or live birth (OR 1.8), secondary recurrent loss, defined as ≥1 births followed by ≥3 successive pregnancy losses with no history of previous stillbirth or live birth (OR 1.3), secondary after giving birth to a boy (OR 1.41), after a complicated delivery (OR 1.57) and ≥3 pregnancy losses before age 30 (OR 1.47). A similar strong association between endometriosis and pregnancy loss was noted on subgroup analyses of women diagnosed in the four decades between 1977-2017, women with adenomyosis and women with adenomyosis only.

Evidence has shown an association between endometriosis and pregnancy loss. However, the present study has also demonstrated an association of endometriosis with recurrent pregnancy losses. As the number of pregnancy losses increased, the strength of the association increased. Presence of adenomyosis alone was also found to be linked to pregnancy losses, particularly recurrent losses. Hence, it is important to make a distinction between endometriosis and adenomyosis.

Reference

1. Boje AD, et al. Endometriosis is associated with pregnancy loss: A nationwide historical cohort study. Fertil Steril. 2023 Jan 3;S0015-0282(22)02134-3. doi: 10.1016/j.fertnstert.2022.12.042.