Endometriosis a risk factor for miscarriage

Women with endometriosis are at higher risk of pregnancy loss and recurrent pregnancy loss, with the risk increase commensurate to the number of losses, according to a study.

This nationwide historical cohort study with a nested case-control analysis used national health registers and included 29,563 women born between 1957 and 1997 and diagnosed with endometriosis between 1977 and 2017. They were age-matched to 295,630 women without endometriosis.

Researchers assessed the number of pregnancy losses in relation to endometriosis and used conditional logistic regression to estimate the associations. The primary endpoints were the numbers of pregnancy losses categorized as 0, 1, 2, and ≥3 losses. The secondary endpoints were the predefined types of pregnancy losses—pregnancy loss (spontaneous demise of a pregnancy until 22 weeks of gestation), primary recurrent pregnancy loss (three or more consecutive pregnancy losses with no prior live- or stillbirth), and secondary recurrent pregnancy loss (one or more births followed by three or more consecutive losses).

Among ever-pregnant women with endometriosis, 18.9 percent, 3.9 percent, and 2.1 percent had 1, 2 and ≥3 pregnancy losses, respectively. These numbers were significantly higher than among controls without endometriosis (17.3 percent, 3.5 percent, and 1.5 percent, respectively).

The gravidity-adjusted odds ratios for 1, 2 and ≥3 pregnancy losses associated with endometriosis were 1.37 (95 percent confidence interval [CI], 1.32–1.42), 1.75 (95 percent CI, 1.62–1.89), and 2.57 (95 percent CI, 2.31–2.85), respectively.

The predefined subgroups of recurrent pregnancy loss—primary, secondary, secondary after giving birth to a boy, after a complicated delivery, and ≥3 pregnancy losses before age 30—all showed a positive association with endometriosis.