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The indirect association of lactation with subsequent perimenopausal body weight
D Rush1, L H Lumey, A C Ravelli
1Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111, USA.
Objective:
We aimed to estimate the relationship of prior breastfeeding to perimenopausal body mass index (BMI) (kg/m2). While most long-term studies of women's body weight after reproductive experience have found a negative relationship between lactation and body weight, most short-term studies found either no impact of lactation on body weight, or decelerated postpartum weight loss among breastfeeding women.
Design:
We performed a retrospective cohort study.
Setting:
The study was done in The Netherlands between 1987 and 1990.
Subjects:
The 1067 singleton females who were born around the time of the Dutch famine (1 August 1944 through 15 April 1946) at The University of Amsterdam Teaching Hospital were all traced and accounted for. This analysis refers to the 671 who were interviewed and for whom all data elements were available.
Analysis:
We related parity and number of children breastfed at least 1 week to BMI at age 45 and at the time of marriage, both calculated from respondents: recall of weight and height, by linear multiple regression analysis, adjusting for potentially confounding variables.
Results:
Among parous women, each additional live birth was associated with a BMI increase of 0.69 kg/m2 (CI = 0.24 to 1.13, P = 0.003), and for each additional child breastfed, the BMI was lower by 0.41 kg m2 (CI = -0.77 to -0.04, P = 0.03) at age 45. However, BMI before any reproductive experience was 0.39 kg/m2 greater (CI = 0.08 to 0.71, P = 0.01) with each additional subsequent birth, and for each additional infant breastfed, 0.34 kg/m2 lower (CI = - 0.60 to - 0.09, P = 0.008).
Conclusions:
The negative relationship of prior breastfeeding to perimenopausal weight was probably not causally related to breastfeeding, since the relationship was present before any reproductive experience. The results could also arisen in part because of biased recall of weight; however, the relationship of parity to perimenopausal BMI was far less attenuated by adjusting for prior BMI than was the association with breastfeeding, lending support to an indirect association of breast- feeding with later BMI.