Table 2.

Preeclampsia, pregnancy-induced hypertension, and maternal breast cancer risk^a

First author and year	Study location	Cases/Controls	Attained age (years)	Comparison	OR/RR/HR (95% CI)	Comments
Case–control, registry-based
Polednak 1983 [29]	United States	314/628	<45	First birth: Preeclampsia/ toxemia (yes vs. no)	0.28 (0.08–1.00)b	Matched on location and time of first delivery. Adjusted for maternal age at first birth
Innes 2004 [16]	United States	2,522/10,052	22–55	First birth: Preeclampsia (yes vs. no)	0.85 (0.65–1.12)	Matched on county of residence and date of delivery. Adjusted for attained age, maternal age at first birth, race, education, infant birthweight, gestational age at delivery, infant sex, abruptio placentae, and multifetal gestation
Case–control, interview-based
Thompson 1989 [84]	United States	4,668/4,635	20–54	Before the end of the most recent term birth: Hypertension (yes vs. no)	0.73 (0.59–0.92)	Matched on attained age and geographic area. Adjusted for attained age, geographic region, parity, age at first birth, and duration of breastfeeding
Talamini 1997 [46]c	Italy	2,569/2,588	20–74	Any birth: First diagnosis of hypertension during pregnancy	By menopausal status: Premenopausal: 1.4 (0.6–3.4) Postmenopausal: 2.3 (1.0–5.4)	Adjusted for study area, attained age, education, parity, and BMI
Troisi 1998 [17]	United States	1,236/1,162	20–44	Any birth: Toxemia vs. never PIH vs. never	0.81 (0.61–1.1) 0.94 (0.73–1.4)	Matched on attained age and geographic area. Adjusted for attained age, site, race, parity/age at first birth, BMI, and menopausal status
Terry 2007 [83]	United States	1,310/1,385	20–98	Any birth: Preeclampsia vs. never	By menopausal status: Premenopausal: 0.99 (0.52–1.88) Postmenopausal: 0.63 (0.41–0.98)	Matched on attained age. Adjusted for attained age, age at first birth, BMI at age 20 and reference date, parity, smoking status, age at menarche, lactation, family history of breast cancer, ethnicity, education, preeclampsia, and PIH. Found stronger protective effects for multiple occurrences of preeclampsia alone or both conditions, but not PIH alone
				PIH vs. never	Premenopausal: 0.89 (0.51–1.56) Postmenopausal: 0.78 (0.51–1.19)
Cohort, registry-based
Richardson 2000 [80]d	United States	205/337	17–44 (baseline)	Index birth: Preeclampsia alone PIH alone Both preeclampsia/PIH	1.57 (0.63–3.88) 0.79 (0.40–1.57) 1.07 (0.60–1.90)	Matched on maternal birth date. Adjusted for age at index pregnancy, age at first full-term pregnancy, and race. Unknown reference group for ORs (assume never). It was not indicated if the index birth was first/last etc.
Vatten 2002 [77]	Norway	5,474/689,183	<30–80	First birth: Preeclampsia and/or PIH vs. neither	By attained age <50 years: 0.81 (0.7–0.9) ≥50 years: 0.81 (0.6–1.1)	Adjusted for attained age, calendar period of diagnosis, age at first birth, and parity
Vatten 2007 [78]	Norway	9,160/691,846	NR	First birth: Preeclampsia and/or PIH vs. neither	Overall: 0.86 (0.78–0.94) By offspring gender Male: 0.79 (0.60–0.90) Female: 0.94 (0.82–1.06)	Adjusted for attained age, age at first birth, length of gestation, parity, marital status and offspring gender. This study includes overlapping data with Vatten et al. [77], but is not an update and different exclusion criteria and modeling approaches were used
Calderon- Margalit 2009 [79]e	Israel	1,624/NR	<20 to ≥40 (baseline)	Any birth: Preeclampsia vs. never	1.37 (1.06–1.78)	Adjusted for age at first birth, and parity

CI confidence interval, OR odds ratio, HR hazard ratio, RR relative risk or rate ratio, PIH pregnancy-induced hypertension, NR not reported, BMI body mass index

^aStudies that did not report covariate-adjusted measures of association are not summarized in the Table {[55] (preeclampsia only), [15] (hypertensive disorders of pregnancy), [81] (preeclampsia only; used the same initial pregnancy cohort as Richardson et al. [80])}

^bThis is a 90% confidence interval

^cHospital-based case–control study

^dThis study was based on linking data from the Child Health and Development cohort to cancer registry data. Exposure assessment was based on medical records

^eUpdate of [82]