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Exhibit L.1 reports the multivariate odds ratios comparing eachcategory to women who never had an induced abortion and had atleast one pregnancy. Researchers were able to interview 845 out of1,011 (83.5 percent) of the eligible cases and 961 out of 1,239 (78per- cent) of the eligible controls. Of the cases, only 689 (81.5percent) had complete information on abortion history, compared to781 (81.3 per- cent) of the eligible controls.

Abortion History	Cases	Controls	Crude OR2	Multivariate OR (95% CI)3
Ever had abortion	210	201		1.5 (1.2–1.9)
1 abortion only	150	142		1.5 (1.1–2.0)
2+ abortions	60	59		1.6 (1.0–2.4)
Age at first abortion
<18	20	15		2.5 (1.1–5.7)
18–19	34	36		1.7 (1.0–3.0)
20–29	115	123		1.3 (1.0–1.7)
30+	41	27		2.1 (1.2–3.5)
Timing of first abortion
Before 1st birth	69	76		1.4 (1.0–2.0)
After 1st birth	74	63		1.5 (1.0–2.2)
Never gave birth	67	62		1.7 (1.2–2.6)
Never had abortion	479	580		––
Never had an abortion and at least onepregnancy1	466	564		––

Note: 1. Estimated from the data. 2. Multivariate ORadjusts for age, family history of breast cancer, religion, age atfirst pregnancy. 3. Both crude and multivariate odds ratioestimates risk relative to women with a least one pregnancy whonever had an induced abortion. Source: Daling et al.(1994).

Calculate the crude odds ratios for each of the abortion historystrata in Exhibit L.1. What is the overall increased risk ofabortion after adjusting for several covariates?