Reproductive Factors and Risk of Uterine Fibroids

Abstract

We analyzed the relation between reproductive history and risk of uterine fibroids using data from a case-control study. Cases were 621 women with histologically confirmed diagnosis of uterine fibroids. Controls were 1,051 non-hysterectomized patients. Compared with nulliparae, parous women had a relative risk (RR) of fibroids of 0.5 [95% confidence interval (CI) = 0.4-0.6], and the risk declined with number of births. The risk of fibroids also decreased with number of induced abortions (RR = 0.8 and 0.6 for women reporting one or two or more abortions, respectively). A total of 24 cases (3.9%) and 19 controls (1.8%) reported a history of infertility (RR = 2.0; 95% CI = 1.1-3.7).

Epidemiological Risk Factors For Fibroid Uterus -A Case Control Study From Kerala

“…There were a higher risk of 13.5 times for women not exposed to passive smoking to develop fibroid. This observation is also similar to other studies in literature 8,13 . Positive family history of fibroid had a 3 times more risk for the occurrence of fibroid, though only 5.6% of cases had a positive family history.…”

“…Similar association is well described in other studies 8,11 . An explanation for this finding is that pregnancy reduces the time of exposure to unopposed oestrogens, whereas nulliparity or reduced fertility may be associated with anovulatory cycle characterized by long term unopposed oestrogens.…”

Etiology and pathogenesis of uterine leiomyomas: a review.

“…A relative risk of fibroids among parous women of 0.5, compared with nulliparae (Parazzini et al 1988), and a progressive decline in risk relative to the number of births have been reported (Lumbiganon et al 1996;Marshall et al 1998a;Parazzini et al 1996a;Ross et al 1986;Sato et al 2000a). An explanation that has been sometimes cited in the literature (Parazzini et al 1996a;Ross et al 1986) for these findings is that pregnancy reduces the time of exposure to unopposed estrogens, whereas nulliparity or reduced fertility may be associated with anovulatory cycles characterized by long-term unopposed estrogens. The alternative possibility exists that uterine fibroids are actually the cause of the infertility, rather than the consequence of it; however, the diminished relative risk of fibroids associated with parity remains essentially the same after exclusion of women with a history of infertility (Marshall et al 1998a).…”

“…Several studies have shown an inverse relationship between parity and the risk of fibroids (Lumbiganon et al 1996;Parazzini et al 1996a;Ross et al 1986;Samadi et al 1996). A relative risk of fibroids among parous women of 0.5, compared with nulliparae (Parazzini et al 1988), and a progressive decline in risk relative to the number of births have been reported (Lumbiganon et al 1996;Marshall et al 1998a;Parazzini et al 1996a;Ross et al 1986;Sato et al 2000a).…”

“…This supposition has been based in part upon the clinical observations that fibroids occur only after menarche, develop during the reproductive years, may enlarge during pregnancy, and frequently regress following menopause. Furthermore, because the risk of fibroids is greater in nulliparous women who might be subject to a higher frequency of anovulatory cycles and obese women with greater aromatization of androgens to estrone in the fat, the concept of unopposed estrogens as an underlying cause of uterine fibroids has sometimes been proposed in the literature (Cramer 1992;Parazzini et al 1996a;Romieu et al 1991;Ross et al 1986). Increased growth of myomas among women taking tamoxifen or receiving transdermal or injected estrogenreplacement therapy further supports the importance of estrogen.…”