OBJECTIVE: To assess the reproductive long-term prognosis of women with and without endometriosis, to explore changes over time, and to quantify the contribution of artificial reproductive techniques.

DESIGN: Cohort study.

SETTING: Denmark 1977-2009.

SAMPLE: Data retrieved from four national registries. Among 15-49-year-old women during the period 1977-82, 24 667 were diagnosed with endometriosis and 98 668 (1:4) women without endometriosis were age-matched.

METHODS: To assess long-term reproductive prognosis, all pregnancy outcomes were identified among the women with and without endometriosis until the end of 2009. To explore changes over time, the endometriosis cohorts were followed for 15 years from the years 1980, 1986, 1992 and 1998, with the corresponding control cohorts. All pregnancy outcomes were categorized into naturally or artificially conceived pregnancies.

MAIN OUTCOME MEASURES: Births, miscarriages, induced abortions, ectopic pregnancies and hydatidiform moles.

RESULTS: Compared with women without endometriosis, women with endometriosis had a lowered relative risk for childbirth of 0.93 (95% confidence interval 0.92-0.95), for miscarriages the relative risk was 1.2 (95% confidence interval 1.2-1.3), ectopic pregnancies were almost twice as many (relative risk 1.9, 95% confidence interval 1.8-2.1), while frequencies of induced abortions were equivalent. The chances for childbirth increased over time from 0.82 to 0.92 (p < 0.001) with successive cohorts, but this was restricted to pregnancies from assisted reproduction.

CONCLUSION: Women with endometriosis have slightly fewer children, but this lessened over time due to artificially conceived pregnancies. The risk for miscarriages and ectopic pregnancies was increased compared with women without the disease.