Research Methods · Study Design

Association of endometriosis and spontaneous abortion: effect of control group selection

Metzger DA, Olive DL, Stohs GF, Franklin RR

Fertility and Sterility, 45(1), 18-22, 1986
DOI 10.1016/s0015-0282(16)49090-4 PMID 3943647
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RRM Academy Synopsis

Miscarriage fell after endometriosis diagnosis with or without surgery

Miscarriage rates fell after diagnosis whether or not infertile women with endometriosis had surgery. In a 1986 chart review of 139 infertile women, about 6 out of 10 pregnancies ended in miscarriage before diagnosis. With expectant management, about 2 out of 10 did. After conservative surgery, none did.

Key Findings

  • Before diagnosis, 41 of 65 pregnancies ended in spontaneous abortion (loss before 20 weeks' gestation), a rate of 63.1%.
  • After conservative surgical resection, 0 of 32 pregnancies ended in spontaneous abortion (0.0%), with no miscarriages at any stage of disease. The pooled comparison with before diagnosis gave P < 0.000001.
  • With expectant management, 6 of 32 pregnancies ended in spontaneous abortion (18.7%), well below the rate before diagnosis (P < 0.0001).
  • Expectant management rates were 16.7% (3 of 18 pregnancies) in mild and 21.4% (3 of 14) in moderate disease.
  • In mild and moderate disease, surgical and expectant groups did not differ significantly in spontaneous abortion rate. The difference reached significance only when all stages were pooled.

Interpretation

The study is a retrospective chart review of consecutive infertility patients seen by one physician in 1977. Women who declined surgery, or became pregnant before it, formed the expectant group. Prior miscarriages were recorded mainly from patient history. Median total follow-up was 1.1 years (range 0.1 to 6.0). Each treatment path had 32 pregnancies. Severe disease had no pregnancies under expectant management. The authors offer possible explanations for the high pre-diagnosis rate: mostly unconfirmed histories, a preselected group who wanted pregnancy, and frequent infertility visits. They write that the data suggest but do not prove that endometriosis may not cause it.

RRM Context

Endometriosis occurs in women who may already have other problems thought to raise miscarriage risk. The authors name luteal phase deficiency and uterine anomalies. Restorative reproductive medicine looks at the whole cycle and both partners before blaming one condition. The authors write that without a control group, spontaneous recovery after early pregnancy loss may be credited to the treatment.

Abstract

Endometriosis has been associated with an increased incidence of spontaneous abortion, compared with the abortion rate of the general population. To assess whether a separate control group would affect these conclusions, we studied 139 consecutive infertility patients with laparoscopically proven endometriosis to determine the incidence of spontaneous abortion. Ninety-five of these patients underwent conservative surgical resection of endometriosis, and 44 patients opted for expectant management. There was no significant difference between these two groups in average age, duration of infertility, or proportion of patients with primary infertility. The average spontaneous abortion rate before diagnosis for all patients was 63.1%. After surgical treatment, the abortion rate dropped to 0% (P less than 0.000001) for all stages of disease. However, even in those patients who received expectant management only, the abortion rate fell to 16.7% and 21.4% for mild and moderate endometriosis, respectively (P less than 0.001). These results suggest that the spontaneous abortion rate in untreated endometriosis may not be as high as previously reported and may not be significantly different from the rate in the general population. The data also emphasize the need for well-defined control groups when assessing the effects of a treatment regimen.

Topics

By this author

Related research

Research Methods › Study Design › Cohort Studies · Endometriosis › Fertility and Outcomes › Conception After Excision · Pregnancy › Early Pregnancy › Miscarriage
PMID 3943647 3943647 DOI 10.1016/s0015-0282(16)49090-4 10.1016/s0015-0282(16)49090-4 Metzger et al. 1986, Metzger 1986

Cite this article

Metzger, D. A., Olive, D. L., Stohs, G. F., & Franklin, R. R. (1986). Association of endometriosis and spontaneous abortion: effect of control group selection. Fertility and sterility, 45(1), 18-22. https://doi.org/10.1016/s0015-0282(16)49090-4