Table III.

History of severe teenage acne and risk of laparoscopically confirmed endometriosis in the NHS II cohort, stratified by infertility history and BMI (<25, ≥25 kg/m²), 1989–2009.

	Never infertile		Ever infertile
	No acne	Acne	No acne	Acne
Number of cases/person-year	3136/986 301	331/82 842	815/57 519	100/5396	P inter
RRa	1.00	1.17 (1.04, 1.31)	1.00	1.28 (1.03, 1.60)	0.53
	BMI < 25		BMI ≥ 25
	No acne	Acne	No acne	Acne
Number of cases/person-year	2326/582 468	246/48 693	1413/414 253	158/35 544	P inter
RRa	1.00	1.14 (1.00, 1.30)	1.00	1.22 (1.03, 1.44)	0.90

^aAdjusted by age, BMI (<18.5, 18.5–22.4, 22.5–24.9, 25.0–29.9, 30.0–34.9, 35.0–39.9 and 40+), BMI at age 18 (<18.5, 18.5–22.4, 22.5–24.9, 25.0–29.9, 30.0–34.9, 35.0–39.9 and 40+), age of menarche (≤11 years, 12–13 years, 14+ years), parity (nulliparous, 1 pregnancies >6 months, 2 pregnancies >6 months, 3 pregnancies >6 months and 4+ pregnancies >6 months), menstrual cycle length at ages 18–22 (<21 days, 21–25 days, 26–31 days, 32–39 days and 40+ days), oral contraceptive use (never, current and past), smoking status (never, past and current), height (<1.60, 1.60–1.65 and 1.70+), age at first birth (<25, 25–29 and 30+), ibuprofen use (yes, no), alcohol drinking at ages 15–17 (non-drinker, 1–3/month, 1/week, 2–4/week, 5–6/week and 7+/week) and ancestry (Caucasian, African American, Hispanic, Asian and others).