Pregnancy weight gain and breast cancer risk

BMC Women's Health

Table 4 Incidence (per 100,000 person years) and unadjusted and adjusted rate ratios (RR)¹ and confidence intervals (CI) on the Cox model for breast cancer by tertiles of estimated total weight gain (kg) in pregnancy (weeks 0–40), and by tertiles of postpartum weight retention.

	Breast cancer cases	Number of women	Incidence	p-value	Unadjusted RR (95% CI)	Adjusted RR (95% CI)¹
Pregnancy weight gain (kg)				0.09
<11	39	696	143		1.18 (0.74–1.88)	1.11 (0.68–1.83)
11–15	33	697	121		1.00 (ref.)	1.00 (ref.)
> 15	51	696	190		1.59 (1.03–2.47)	1.62 (1.03–2.53)
Postpartum weight retention (kg) ²				0.33
<3	26	558	121		1.00 (ref.)	1.00 (ref.)
3–5	35	539	170		1.29 (0.72–2.34)	1.36 (0.73–2.54)
>5	35	545	170		1.54 (0.87–2.74)	1.56 (0.85–2.86)
Pregnancy weight gain (kg), case-control study ³
<11	19	167	-	-	1.01 (0.54–1.91)	0.95 (0.49–1.84)
11–15	19	170	-	-	1.00 (ref.)	1.00 (ref.)
> 15	27	159	-	-	1.50 (0.83–2.69)	1.48 (0.81–2.69)

¹ Adjusted for age at menarche, age at first birth, age at index pregnancy, parity (at index birth) and body mass index (BMI) before pregnancy. For the RR for postpartum weight retention, adjusted also for pregnancy weight gain (weeks 0–40).
² Weight on postpartum day 51, range 40–78, compared to pre-pregnancy weight.
³ Adjusted for age at menarche, age at first birth, age at index pregnancy, parity (at index birth), BMI before pregnancy, and BMI during the hospital visit in average 29 years after pregnancy.

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