Obstetrics & Gynecology 2007;109:729-738
Lactation and Changes in Maternal Metabolic Risk Factors
Erica P. Gunderson, PhD1, Cora E. Lewis, MD, MSPH2, Gina S. Wei, MD, MPH3,
Rachel A. Whitmer, PhD1, Charles P. Quesenberry, PhD1 and Steve Sidney, MD,
MPH 

OBJECTIVE: To examine the relationship between duration of lactation and
changes in maternal metabolic risk factors. 

METHODS: This 3-year prospective study examined changes in metabolic risk
factors among lactating women from preconception to postweaning and among
nonlactating women from preconception to postdelivery, in comparison with
nongravid women. Of 1,051 (490 black, 561 white) women who attended two
consecutive study visits in years 7 (1992-1993) and 10 (1995-1996), 942 were
nongravid and 109 had one interim birth. Of parous women, 48 (45%) did not
lactate, and 61 (55%) lactated and weaned before year 10. The lactated and
weaned women were subdivided by duration of lactation into less than 3
months and 3 months or more. Multiple linear regression models estimated
mean 3-year changes in metabolic risk factors adjusted for age, race,
parity, education, and behavioral covariates. 

RESULTS: Both parous women who did not lactate and parous women who lactated
and weaned gained more weight (+5.6, +4.4 kg) and waist girth (+5.3, +4.9
cm) than nongravid women over the 3-year interval; P<.001. Low-density
lipoprotein cholesterol (+6.7 mg/dL, P<.05) and fasting insulin (+2.6
microunits, P=.06) increased more for parous women who did not lactate than
for nongravid and parous women who lactated and weaned. High-density
lipoprotein cholesterol decrements for both parous women who did not lactate
and parous women who lactated and weaned were 4.0 mg/dL greater than for
nongravid women (P<.001). Among parous, lactated and weaned women, lactation
for 3 months or longer was associated with a smaller decrement in
high-density lipoprotein cholesterol (-1.3 mg/dL versus -7.3 mg/dL for less
than 3 months; P<.01). 

CONCLUSION: Lactation may attenuate unfavorable metabolic risk factor
changes that occur with pregnancy, with effects apparent after weaning. As a
modifiable behavior, lactation may affect women's future risk of
cardiovascular and metabolic diseases. 

LEVEL OF EVIDENCE: II 

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