A dose-response meta-analysis of the relationship between number of pregnancies and risk of gynecological cancers.

Background: Despite several investigations, the association between the number of pregnancies and gynecological cancers remains inconclusive. To address this issue, we conducted a dose-response meta-analysis of observational studies.

Methods: We searched PubMed, Web of Science, and Scopus databases up to Jun 8, 2023, to identify observational studies that examined the association between the number of pregnancies and gynecologic cancers. To assess the heterogeneity across studies, we used the χ² test and I² statistics. We also explored the possibility of publication bias using Begg's and Egger's tests. The overall effect sizes were reported as odds ratios (ORs) with a 95% confidence interval (CI) using a random-effects model.

Results: Out of the 87,255 studies initially identified, a total of 101 studies involving 8,230,754 participants were included in the final meta-analysis. Our analysis revealed a positive trend between the number of pregnancies and cervical cancer; however, this association was not found to be statistically significant except for fifth pregnancy. Conversely, our findings showed a significant decreasing trend between the number of pregnancies and the risk of endometrial and ovarian cancers. There was insufficient evidence to establish a relationship between the number of pregnancies and the risk of vaginal, vulvar, and fallopian tube cancers.

Conclusions: Our study found a positive trend between the number of pregnancies and cervical cancer and a significant decreasing trend between the number of pregnancies and endometrial and ovarian cancers. These findings may have implications for counseling women about their reproductive health and the potential risks and benefits of pregnancy.