Primary infertility and oral contraceptive steroid use.

OBJECTIVE

To determine the association between combined monophasic oral contraceptive (OC) use and primary infertility.

DESIGN

Case-control.

SETTING

Women serving as controls of the Cancer and Steroid Hormone Study.

PARTICIPANTS

Women were 19 to 40 years of age at first conception or infertility diagnosis. Based on 24 consecutive months of unprotected intercourse without a recognized conception, 419 nulligravid women had primary infertility; controls were 2,120 fertile women. A calendar of each women's reproductive history was used to determine fertility status and contraceptive use before infertility diagnosis or first conception.

MAIN OUTCOME MEASURE: Primary infertility.

RESULTS

Combined monophasic OC use was associated with a lower frequency of primary infertility, particularly among younger (age 20 years) compared with older women (age 30 years) after adjusting for barrier method use and education. A similar association was found for duration of OC use. When adjusted for age at first conception or infertility and barrier method, both higher (> 50 micrograms) and lower (< or = 50 micrograms) estrogen dose use were associated with decreased risk of primary infertility.

CONCLUSION

Combined monophasic OC use was associated with a lower frequency of primary infertility.