Endometriosis may be tied to pregnancy complications


Researchers in Japan have found that endometriosis ups risks of certain complications.

Findings from a new large prospective cohort study provide further evidence that endometriosis is a risk factor for obstetrical complications and show that the increased risk affects both women with and without a history of assisted reproduction technology (ART) therapy.1

“A limited number of previous studies suggested a relationship between endometriosis and adverse pregnancy outcomes, but those investigations have been criticized because of the small number of cases included and inability to control for confounding variables that have also been associated with adverse pregnancy outcomes, such as infertility treatment,” said Tasuku Harada, MD, Professor and Chair, Department of OB GYN, Tottori University, Japan.

“To our knowledge, ours is the first study to show that endometriosis has an adverse impact on the occurrence of obstetrical complications after adjusting for the influence of ART, and we were surprised by the results.”

The research was conducted recognizing that because women with a history of endometriosis are often infertile, they may receive ART that by itself increases the risk of obstetrical complications.

The investigators reviewed data from 9,86 pregnant women who had a singleton pregnancy and gave birth, had a stillbirth, or whose pregnancy was terminated with abortion between February 2011 and December 2011. The women were identified from the Japan Environment & Children’s Study, which is an ongoing prospective birth cohort study created to investigate how environmental factors may affect childhood health and development.

Of the women included in the study, 4,119 (44.8%) had obstetrical complications-threatened abortion, threatened premature delivery, premature rupture of membranes (PROM), gestational diabetes, preeclamspia, placenta previa, and/or placental abruption. A total of 330 (8.0%) women had a self-reported history of endometriosis. The vast majority of women with a history of endometriosis conceived naturally (266/330, 80.6%).

The incidence of obstetrical complications among women with and without a history of endometriosis was 54.5% (180/330) and 44.5% (3,939/8,856), respectively. In a multivariable analysis adjusting for potential confounders of maternal age at time of delivery, smoking status, and alcohol ingestion, women with a history of endometriosis had a 1.5-fold significantly increased risk for obstetrical complications overall.

Analyses of specific types of complications found women with a history of endometriosis had significantly increased risks for threatened preterm delivery (1.5-fold), placenta previa (6.4-fold), and placental abruption (3.5-fold) compared to women without a history of endometriosis.

Logistic regression analyses were performed with women categorized into four groups based on history of endometriosis and receipt of infertility treatment in order to eliminate confounding by infertility treatment. After controlling for other confounders, women with endometriosis who conceived naturally had significantly increased risks for obstetrical complications, preterm PROM (2.5-fold), placenta previa (3.3-fold), and placental abruption (3.4-fold). In addition, women with a history of endometriosis had a significantly higher risk for preterm PROM and placenta previa compared with women without endometriosis who conceived naturally or after infertility treatment (other than ART therapy), 2.1-fold and 3.4-fold, respectively.

“Based on our findings, we think it may be important for obstetricians to inform women with a history of endometriosis that they have an increased risk of PROM and previa,” Dr Harada told Contemporary OB/GYN.

The investigators noted that determination of endometriosis by self-report is a limitation of their study. In addition, they were not able to determine whether endometriosis was active during pregnancy or if treatment and what kind was given before pregnancy.



1. Harada T, Taniguchi F, Onishi K, et al; Japan Environment & Children’s Study Group. Obstetrical complications in women with endometriosis: a cohort study in Japan. PLoS One. 2016 Dec 22;11(12):e0168476.

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