Erica P. Gunderson1
(1)
Division of Research, Epidemiology and Prevention Section, Kaiser Permanente Northern California, Oakland, CA, USA
Erica P. Gunderson
Email: epg@dor.kaiser.org
Abstract
Lactating women exhibit more favorable cardiometabolic profiles than non-lactating women, yet lasting effects on future disease risk remain unclear. Among women in general, lactation may protect against development of the metabolic syndrome and type 2 diabetes in midlife. However, studies of lactation and metabolic disease after pregnancy among women with gestational diabetes mellitus (GDM) are limited by reliance on self-report of type 2 diabetes or variable time intervals for screening after GDM pregnancy. Among the offspring, consensus expert panels have concluded that breastfeeding reduces the risk of overweight by 22% to 24% among children and adolescents in developed countries. Yet, breastfeeding may not have similar effects on the offspring of women with GDM during pregnancy. Studies of breastfeeding and future diabetes in the offspring have mostly involved heterogeneous samples that combined offspring of mothers who had GDM and mothers who had pre-gestational diabetes. Given that lactation and breastfeeding promote lasting health benefits among women and children in the general population, further research targeting women with a history of GDM and their offspring is recommended.
22.1 Introduction
Lactation has been associated with more favorable cardiometabolic risk factor profiles during the postpartum period among women in general, and those with a history of gestational diabetes mellitus (GDM) during pregnancy.1, 2Among women in general, evidence suggests that extended lactation may protect against future development of type 2 diabetes3 and the onset of the metabolic syndrome in midlife.4,5However, among women with a history of GDM, evidence is based on two studies which have yielded inconsistent results. Studies examining increasing months of lactation have reported a null association with incident type 2 diabetes3, and a 44 to 86% lower incidence of the metabolic syndrome.6
Evidence is also equivocal that breastfeeding influences the long-term health of the offspring of mothers with GDM during pregnancy. Breastfeeding has been associated with beneficial, adverse, or no effects on development of overweight and type 2 diabetes for the offspring of women with diabetes during pregnancy.7 Early infant feeding practices and postnatal influences may be particularly important for offspring of mothers with GDM, because they are more likely to become overweight, and to develop impaired glucose tolerance, the metabolic syndrome, and type 2 diabetes later in life.8–13
In this chapter, we critically examine the available data that lactation influences the development of cardiometabolic risk factors, the metabolic syndrome, and type 2 diabetes among women in general and those with a history of GDM. In addition, we examine the evidence that breastfeeding may affect development of overweight and diabetes among the offspring of mothers with a history of GDM pregnancy. Finally, we provide recommendations for future research.
22.2 Lactation and Women’s Health
22.2.1 Effects of Lactation on Cardiometabolic Risk Factors and Long-term Disease Risk
Lactation has favorable effects on cardiometabolic risk profiles during the postpartum period among women with and without a history of GDM. The maternal risk factors that may be influenced by lactation include plasma lipid, insulin and glucose profiles, body fat distribution and postpartum weight loss. Although the effects of lactation on cardiometabolic risk factors may persist postweaning, one study6provides direct biochemical evidence that these favorable changes in postpartum risk factor profiles persist years later to lower risk of incident disease in women later in life.
22.2.2 Studies of Risk Factors Among Women in General
Lower blood glucose and insulin concentrations, along with higher rates of glucose production and lipolysis, have been observed among lactating women compared with nonlactating women.14 Moreover, plasma total cholesterol and triglyceride levels declined more rapidly from delivery to 3–5 months postpartum in lactating women,15,16 and their lipid profiles were more favorable (i.e., lower plasma low-density lipoprotein cholesterol or LDL-C, triglycerides and higher high-density lipoprotein cholesterol or HDL-C) by 6 months postpartum.17,18 However, these studies did not control for differences in preconception lipid profiles and obesity, postpartum weight loss, or lifestyle behaviors. Recently, in 67 Brazilian women given oral glucose tolerance tests at 12–18 months postpartum, increasing duration of lactation was inversely associated with the area under the insulin curve independent of body adiposity.19 These data suggest that lactation may be an important factor in reversal of gestational hyperlipidemia and have lasting favorable effects on women’s health. However, these studies do not provide evidence for lasting effects because they did not examine postweaning levels.
Gunderson et al2 examined changes in cardiometabolic risk factors from preconception to an average of 13 months postweaning (range of 2–24 months) among women who gave birth during a 3-year interval. Postweaning levels of HDL-C were 6 mg/dL higher among women who lactated for 3 months or longer vs. less than 3 months (p < 0.01), and parous women who did not lactate had a 2.6 uU higher fasting insulin postpartum (p = 0.06) given similar preconception levels and weight gain.2 These lasting effects on plasma HDL-C levels associated with lactation (i.e., postweaning) are important because low plasma HCL-C is a strong predictor of type 2 diabetes in women.
Obesity and weight gain contribute to development of type 2 diabetes. Yet, evidence is equivocal about whether lactation promotes greater loss in fat mass.20 One study of body composition found a 2 kg greater loss in total body fat mass for lactating vs. nonlactating women that did not reach statistical significance.21 Studies that measured body weight changes from before or during early pregnancy (not self-reported) consistently reported that lactating vs. nonlactating women had lower postpartum weight retention, greater weight loss, and more rapid return to pregravid weight within 6–12 months.22–25 These studies carefully assessed lactation and demonstrate that both intensity and duration of lactation are important determinants of postpartum weight loss. Longer duration of lactation has also been associated with lower maternal weight gain 10–15 years later.26,27
22.2.3 Lactation and Future Diabetes Risk Among Women in General
To our knowledge, only two studies have examined lactation duration and future risk of diabetes among women in general. The Nurses’ Health Study II (NHS II) found that lactation for 4–6 months and up to 2 years was associated with a 25–40% lower incidence of self-reported DM among women aged 24–43 yrs at baseline who reported a birth within the past 15 years of follow-up.3 The association was independent of current BMI and other risk factors, and risk reductions were stronger with exclusive lactation.3 In the Shanghai Women’s Health Study, Villegas et al. found that lactation for 4 years or longer reported when women were aged 40–70 was associated with a 10–12% lower incidence of DM that varied by years since last birth and number of children.28 However, plasma glucose levels were not measured before, during, and/or after pregnancy in either study of the long-term effects of lactation on development of diabetes in mid and late life.
22.2.4 Lactating versus Non-Lactating Women with a Recent GDM Pregnancy
Lactation also favorably affects maternal glucose tolerance and lipid profiles after GDM pregnancy. Fourteen lactating compared with 12 nonlactating women with previous GDM had higher insulin sensitivity, glucose effectiveness and first phase insulin response to glucose (AIRg) assessed by Bergman’s Minimal Model, but statistical significance was not reached.29 However, the disposition index (insulin sensitivity multiplied by AIRg) was 2.5 times higher (129.9 ± 26.0 vs. 53.4 ± 18.0 × 10(−4) min(−1); p < 0.05) in lactating vs. nonlactating women matched for age, weight, postpartum weight loss, and exercise habits.29 These data suggest that women who lactated after GDM pregnancy had improved insulin sensitivity and β-cell function.
A series of cross-sectional and follow-up studies (Table 22.1) of Latinas with history of GDM provide evidence that lactation influences glucose metabolism.1, 30–32 For example, lactating women had better glucose tolerance at 4–12 weeks postpartum; a lower total area under the glucose tolerance curve (AUC) (17.0 ± 4.2 vs. 17.9 ± 5.0 g/min/dL), and lower fasting serum glucose (93 ± 13 vs. 98 ± 17 mg/dL) and 2-h OGTT glucose levels (124 ± 41 vs. 134 ± 49 mg/dL) after controlling for BMI, maternal age and insulin use during pregnancy.1 The prevalence of type 2 diabetes was lower for lactating (4.2%) vs. nonlactating (9.4%) women with recent GDM.1 Buchanan et al examined 122 Latinas with normal fasting glucose and no insulin use during GDM pregnancy and found that those diagnosed with diabetes within 6 months postpartum were less likely to be currently lactating (42%) than those with normal glucose tolerance (71%); p = 0.03.31 These data suggest that lactation may have favorable effects on glucose tolerance during the postpartum period.
Table 22.1
Association of lactation status or lactation duration with Risk of Type 2 Diabetes Mellitus (DM) or the Metabolic Syndrome among Women with a history of GDM
|
Reference |
Study design, years |
n, GDM pregnancy |
Study population |
Lactation measure |
Type 2 DM definition |
Time since delivery |
Type 2 DM outcome |
Conclusion |
|
Kjos et al1 |
Cross-sectional 1990–1991 |
809 |
Latinas attending family planning clinic |
Yes/no at 4–16 weeks postpartum |
2-h 75-g OGTT |
4–16 weeks |
Prevalence: 9.4% in nonlactating 4.2% in lactating |
Lower prevalence of diabetes p = 0.01 in lactating |
|
Kjos et al30 |
Retrospective analysis 1987–1994 |
671 |
Latinas in central Los Angeles |
Yes/no at 4–16 weeks postpartum |
2-h 75-g OGTT |
Variable follow-up, Within 7.5 years |
Incidence rate: 1.1 cases/1,000 person-years (95%CI: 0.9–1.9) |
No association of lactation with DM in bivariate analyses |
|
Buchanan et al31 |
Cross-sectional 1993–1995 |
122 normal fasting glucose, diet-control |
Latinas in central Los Angeles |
Yes/no at 1–6 months |
75-g OGTT and FSIGTs |
1–6 months |
Overall prevalence 10% |
DM less likely to be lactating than non-DM (42% vs. 71%) p= 0.03 |
|
Buchanan et al32 |
Longitudinal 1993–1997 |
91 |
Latinas in central Los Angeles |
Yes/no at 11–26 months postpartum |
75-g OGTT and FSIGTs |
15-month interval, 11–26 months |
Overall cumulative incidence 15% |
No differences in lactation prevalence for DM vs. normal (25% vs. 15.4%) p = 0.41 |
|
Stuebe et al3 |
Retrospective cohort 1989–2003 |
Not reported age 24–43 years in 1989 |
The Nurses’ Health Study cohort |
Total lifetime months of lactation for pregnancies |
Self-report |
Variable, up to 14 years |
Incidence rate: 6.24 cases per 1000 person-years |
No significant association |
|
Gunderson6 |
Prospective Cohort 1985-2006 |
84, Aged 18–30 in 1985 |
CARDIA, Multi-center 50% White 50% Black |
Total months of lactation, all pregnancies |
Fasting and 75-g OGTT and other measures* |
Average 8 years |
Metabolic Syndrome Incidence rate*: 22.1 per 1,000 person-years |
44% to 86% lower incidence; p= 0.03 >1 to >9 months versus 0–1 month |
DM diabetes mellitus; GDM gestational diabetes mellitus, *The Metabolic Syndrome instead of Type 2 DM
22.2.5 Lactation and Future Diabetes Risk Among Women with a History of GDM
Less evidence is available to determine whether lactation has lasting effects on glucose metabolism to prevent development of type 2 diabetes in women with a history of GDM. Studies that examined lactation and incidence of diabetes among women with a history of GDM are shown in (Table 22.1). However, several studies assessed lactating versus non-lactating women at the early postpartum glucose tolerance test (i.e., 1–4 months postpartum) rather than lactation duration. Specifically, among Latinas in central Los Angeles, lactation at 4–16 weeks postpartum was not associated with development of type 2 diabetes within 7.5 years after delivery.30 For 91 Latinas, lactation status (yes/no) at testing did not differ by type 2 diabetes diagnosis at 11–26 months after GDM pregnancy.32 Only two studies have assessed lactation duration and disease incidence years later specifically among women with a history of GDM. A retrospective analysis of women with a history of GDM in the NHS cohort found no association between lifetime lactation or other lifestyle behaviors (i.e., diet, exercise habits) and incidence of type 2 diabetes several years after delivery.3 However, limitations of these studies included retrospective analysis, limited assessment of lactation, nonuniversal postpartum screening for diabetes, no plasma glucose measurements before, during, or after pregnancy, self-report of subsequent type 2 diabetes, and no data on lifestyle behaviors. In the NHS cohort, diabetes screening was not conducted prospectively after delivery and diabetes status was ascertained by self-report. The Coronary Artery Risk Development in Young Adults (CARDIA) study,6 measured cardiometabolic risk factors prospectively, both before and after pregnancies during 20 years of follow-up, and assessed lactation duration in relation to incidence of the metabolic syndrome among women with and without a history of GDM. In 702 nulliparas who went on to give birth during follow-up, increasing months of lactation was associated with lower incidence of the metabolic syndrome; 44 to 86% lower among women with a history of GDM and 39 to 56% lower among women with no history of GDM several years post-weaning. These findings suggest that lactation may have persistent favorable effects on women’s cardiometabolic health, and effects may be stronger among women with a history of GDM.6
22.2.6 Lactogenesis and History of GDM
Effects of GDM pregnancy on lactogenesis have rarely been studied. One small clinical study of women with recent GDM reported no marked delays in lactogenesis based on similar concentration of lactose in the colostrum at 40–50 h postpartum for GDM women compared with control women.33 However, GDM women had more difficulty expressing colostrum from their breasts during the first 2 days of lactation.33 Moreover, maternal obesity may delay the onset of lactogenesis34,35 due to lower physiological levels of prolactin in response to suckling.34 Delayed milk production has been associated with lower rates of breastfeeding and shorter duration among obese women.35Furthermore, medical management of newborns that involves provision of supplemental milk feedings (i.e., neonatal hypoglycemia) may also interfere with maternal milk production.
Preliminary evidence suggests that lactation may confer long-term protection against development of type 2 diabetes later in life, among women in general. The evidence for an association between lactation and lower risk of cardiometabolic disease in women with a history of GDM is inconclusive given that prospective, population-based studies have not been conducted. Future studies should employ standardized screening methods for diabetes diagnosis at regular intervals, assess both lactation duration and exclusivity, and control for potential confounders including gestational glucose tolerance, maternal lifestyle and sociodemographics.
22.3 Breastfeeding and Health of the Offspring
22.3.1 General Population and Development of Overweight
In developed countries, evidence supports a robust protective association between breastfeeding and becoming overweight during childhood and adolescence, even after accounting for maternal obesity and family lifestyle behaviors.36,37 In 2007, consensus expert panels concluded that breastfeeding reduces the risk of overweight by 22–24% in children and adolescents,38,39 with attenuation after adjustment for parental anthropometry, socioeconomic status, and birth weight.39 The consistency of these associations from infancy to adulthood, suggests that breastfeeding may have lasting protective effects independent of dietary intake and physical activity later in life.37 Because studies have been conducted primarily in European and Caucasian populations, whether breastfeeding protects against overweight in childhood and adolescence among minority groups is unclear. A caveat arises from the observational data that breastfeeding may be a marker for more healthful behaviors in families rather than by exerting a true biological effect.
Nonetheless, biologic mechanisms may explain breastfeeding’s protection against future overweight. Breast milk’s unique biochemical constituents and nutrient composition may favorably affect infant growth and regulate energy balance. For example, relative to formula feeds, breast milk contains lower protein levels. Higher protein levels in early life have been linked to higher BMI later in life in some,40,41 but not all studies.42 Higher insulin levels have also been reported in formula fed compared with breastfed babies.43 Behavioral aspects may also contribute the favorable effects of breastfeeding on optimal growth and development of energy balance.
22.3.2 Offspring of Mothers with Diabetes During Pregnancy: Development of Overweight
Evidence is equivocal that breastfeeding affects the future health of offspring whose mothers who had diabetes during pregnancy.44 Of four studies (Table 22.2), the risk of childhood or adolescent overweight was higher,45,46 not different,47 and lower48 for breastfeeding vs. not breastfeeding among offspring whose mothers had diabetes (either GDM or pregestational diabetes) during pregnancy. One nonrandomized, longitudinal study compared early intake of breast milk from diabetic mothers (83 type 1 diabetes, 29 GDM) with banked donor breast milk during the first week of life45 and during the second to fourth weeks of life, controlling for the first week.46 Highest vs. lowest breast milk intake from diabetic mothers during the first week of life was associated with a twofold higher (OR = 1.91; 95%CI:1.10–3.30) risk of overweight at age 2, defined as relative body weight above 110%. The association was strengthened (OR = 2.59; 95%CI:1.32–5.04) after adjusting for age, sex, type of maternal diabetes, and maternal BMI.45 The prevalence of impaired glucose tolerance was lower among 2-year-olds who were fed highest vs. lowest amounts of banked donor breast milk in the first week of life (OR = 0.19; 95%CI:0.05–0.70).45 In the same cohort, breast milk intake during the second to fourth weeks of life (OR = 1.61; 95%CI:0.76–3.42) and duration of breastfeeding were not associated with risk of overweight or with impaired glucose tolerance at age 2 adjusted for early neonatal breast milk intake and other covariates.46 However, study subjects were not randomized to donor-banked breast milk, which may have introduced selection bias and residual confounding. Further, the first study did not report the total volume of diabetic breast milk in the first week of life, and neither study assessed the severity of maternal gestational and postpartum hyperglycemia.45
Table 22.2
Association of breastfeeding with risk of overweight among offspring of mothers with diabetes during pregnancy
|
Author (reference) |
Study design |
n, mothers type of DM during pregnancy |
Study population |
Breastfeeding measure |
Obesity definition |
Offspring age range |
OR 95% CI |
Covariates adjusted |
|
Mayer-Davis et al47 |
Retrospective cohort, 1996 |
GDM 417 PG 56 (self-report) |
Nurses’ Health Study, GUTS |
Exclusive breastfeeding vs. exclusive formula |
BMI ≥25 kg/m2 (self-reported weight and height) |
9–14 years in 1996 |
0.62 (0.24–1.60) |
Age, sex, race, Tanner stage, maternal BMI, smoking, income, birth order, diet, physical activity, gestational age |
|
Schaefer-Graf et al48 |
Prospective cohort, 1995–2000 |
GDM 324 |
Berlin, Germany |
Retrospective duration >3 months vs. ≤3 months |
BMI ≥90th percentile in cohort |
2–8 years (mean 5.4 years) |
0.55 (0.33–0.91) |
Parental obesity, birth weight percentile |
|
Rodekamp et al46 |
Lontitudinal 1980–1989 |
T1DM 83 GDM 26 |
Berlin, Germany |
2nd–4th week of life, highest tertile of donor-banked breast milk |
RW >110% |
2 years |
1.61 (0.76–3.42) |
Diabetic breast milk volume 1–7 day life and other covariates from Plagemann et al30 |
|
Plagemann et al45 |
Longitudinal 1980–1989 |
T1DM 83 GDM 26 |
Berlin, Germany |
1–7 days of life, highest tertile of donor-banked breast milk |
RW >110% |
2 years |
2.59 (1.32–5.04) |
Birth weight, gestational age, sex, maternal BMI, type of maternal diabetes |
DM diabetes mellitus; RW relative weight; T1DM type 1 diabetes mellitus; GDM gestational diabetes mellitus; BMI body mass index; PG pregestational diabetes
Other studies found that breastfeeding protected against overweight during childhood and adolescence in the offspring of mothers with GDM. The NHS of Offspring examined youth aged 9–14 years whose mothers had diabetes during pregnancy (417 GDM, 56 pregestational diabetes) and found a lower, but nonsignificant association for ever vs. never breastfed with risk of overweight (OR = 0.62; 95%CI:0.24–1.60).47 Among German mothers with GDM and their offspring (n = 324, aged 2–8 years), exclusive breastfeeding for 3 months or longer was associated with a lower risk of overweight (0.55; 95%CI:0.33–0.91), but only among offspring of obese mothers.48
These conflicting findings may be related to the differences in the age that overweight was ascertained for subjects (i.e., early ages of 2–3 years are much less predictive of overweight status than at older ages). Another limitation is that most studies involved heterogeneous samples where offspring of mothers with pregestational diabetes during pregnancy were included along with offspring of mothers with GDM. Further, none of the studies controlled for the intrauterine metabolism (i.e., degree of maternal glycemic control) or postnatal environment.
22.3.3 Offspring of Women with Diabetes during Pregnancy: Development of Type 2 Diabetes
Breastfeeding may be associated with a lower prevalence of type 2 diabetes in adulthood and lower incidence of type 2 diabetes in childhood (Table 22.3) among offspring whose mothers had diabetes during pregnancy. The studies included indigenous North American populations with high prevalence of type 2 diabetes and a multiethnic US population. In Pima Indians, exclusive breastfeeding compared with exclusive bottle-feeding was associated with a lower prevalence of type 2 diabetes (OR = 0.41; 95%CI:0.18–0.93) among offspring 10–39 years of age adjusted for age, sex, parental diabetes, and birth weight,49 but the study did not examine maternal diabetes during pregnancy. A subsequent analysis of Pima Indians found that exclusive breastfeeding (>2 months) vs. nonbreastfeeding was associated with a lower prevalence of type 2 diabetes (OR = 0.56; 95%CI:0.41–0.76) in 551 offspring of mothers without diabetes during pregnancy.50 But no association was found for 21 offspring of Pima mothers with diabetes during pregnancy; prevalence of type 2 diabetes was 30.1% for exclusively breastfed and 43.5% for not breastfed adjusted for age, sex, birth weight, birth date, and the presence of DM in either parent.50
Table 22.3
Association of breastfeeding with risk of type 2 diabetes or impaired glucose tolerance among offspring of mothers with diabetes during pregnancy (mixed GDM and pregestational diabetes)
|
Reference |
Study design |
n, Mother’s type of DM during pregnancy |
Study population |
Breastfeeding measure |
T2DM outcome definition |
Offspring age range |
OR (95%CI) or percent with DM |
Covariates adjusted |
|
Mayer-Davis et al52 |
Case–control |
Any DM: Cases 16 Controls 8 |
SEARCH Diabetes in youth |
Ever vs. Never BF |
Provider diagnosed, T2DM 80 Control 167 |
10–21 years |
0.43 (0.19–0.99) |
Sex, age, race, family history DM, maternal attributes, child BMI z-score |
|
Young et al51 |
Case–control 2000–2001 |
T1DM 14 GDM 22 None 102 |
Native Canadian, Manitoba |
Duration >12 months vs. none |
T2DM 46 Control 92 Diagnosis <18 years, FPG ≥126 mg/dl |
<18 years |
0.24 (0.13–0.99) |
Age, sex-matched type of maternal diabetes |
|
Pettit et al50 |
Longitudinal 1978 |
75-g OGTT during pregnancy GDM 21 None 551 |
Pima Indians |
Exclusive BF for ≥2 months vs. none |
75-g OGTT WHO criteria Child every 2 years since age 5 years |
10–39 years |
30.1 vs. 43.5% |
None |
|
Pettit et al49 |
Longitudinal 1978 |
Not measured during pregnancy n = 720 |
Pima Indians |
Exclusive BF for >2 months vs. none |
75-g OGTT WHO criteria, Prevalent T2DM |
10–39 years |
0.41 (0.18–0.93) |
Age, sex, birth year, parental diabetes, relative weight, birth weight |
|
Plagemann et al45 |
Longitudinal nonrandomized 1980–1989 |
T1DM 83 GDM 29 |
Berlin, Germany |
1st–7th days of life donor-banked breast milk vs. diabetic breast milk |
IGT based on 2-h OGTT 1.75-g glucose/kg body weight |
2 years |
0.19 (0.05–0.70) |
Birth weight, sex, age, gestational age, relative birth weight, maternal BMI, type of maternal DM |
|
Rodekamp et al46 |
Longitudinal nonrandomized 1980–1989 |
T1DM 83 |
Berlin, Germany |
2nd–4th week of life donor-banked breast milk |
IGT based on 2-h OGTT 1.75-g glucose/kg body weight |
2 years |
0.66 (0.22–2.02) |
Volume of diabetic breast milk in first week of life and others |
OGTT oral glucose tolerance test; IGT impaired glucose tolerance; BF breastfed; T1DM type 1 diabetes mellitus; T2DM type 2 diabetes mellitus; GDM gestational diabetes mellitus
Case–control studies have consistently reported that breastfeeding is associated with lower rates of offspring diabetes. A case–control study of 46 Native Canadian children diagnosed with diabetes before age 18 years and 92 age- and sex-matched controls found a lower OR of type 2 diabetes among offspring who were breastfed 12 months or more vs. none (OR = 0.24;95% CI:0.13–0.84) adjusted for type of maternal diabetes during pregnancy (type 1 diabetes, GDM, or none).51 A case–control study of African American, Hispanic, and non-Hispanic white youth with type 2 diabetes (n = 80) and 167 controls aged 10–21 years, SEARCH for Diabetes in Youth, found a protective association between breastfeeding duration and incidence of type 2 diabetes (OR = 0.43; 95%CI:0.19–0.99) adjusted for 12 covariates.52
Composition of the breast milk of diabetic mothers may vary based on glucose control. For example, higher and more variable glucose levels in breast milk have been found for moderately controlled diabetic women vs. nondiabetic women.53 Based on these limited data, evidence is insufficient to determine whether breastfeeding prevents type 2 diabetes in the offspring of women with GDM, or whether breast milk from diabetic mothers has beneficial or detrimental effects on the growth and health of their infants.44
22.4 Conclusions
Lactation is a modifiable health behavior with the potential to beneficially affect the long-term health of women and their offspring. Whether lactation confers the same benefits to women with a history of GDM and their children has yet to be determined conclusively. The American Academy of Pediatrics recommends that all infants should be exclusively breastfed through 6 months of age and that breastfeeding should continue until the infant is 1 year of age.54Although 80% of US women initiate lactation, 45% report “any” breastfeeding at 6 months and less than 20% report “exclusively” breastfeeding their infants at 6 months. Thus, increasing lactation rates among women may have positive effects on both infant and maternal health in the general population.
Clinical and epidemiologic evidence support the hypothesis that lactation has lasting effects on maternal glucose tolerance for the general population. In the NHS, women who lactated for 4–6 months and up to 2 years experienced a 25–40% lower incidence of self-reported type 2 diabetes, and exclusive lactation was associated with a 35–40% lower risk. In the NHS retrospective analysis, similar associations were not found among women with GDM. In CARDIA, longer duration of lactation was associated with a 2- to 7-fold lower incidence of the metabolic syndrome within 8 years after delivery among both women with a history of GDM, and among women without at history of GDM. Lactation has favorable effects on maternal glucose tolerance during the postpartum period after GDM pregnancy, but evidence is insufficient to conclude that these effects endure post-weaning, or that lactation influences development of type 2 diabetes in women years later.
An abundance of evidence from developed countries supports a robust association between breastfeeding and lower risk of becoming overweight during childhood and adolescence, even after accounting for maternal obesity and family lifestyle behaviors. However, evidence is inconclusive that breastfeeding confers the same protection against obesity for offspring of women with a history of GDM as is reported in the general population. Since 1986, the American Diabetes Association has recommended that women with GDM be encouraged to breastfeed.55,56 The Fourth International Workshop-Conference on Gestational Diabetes Mellitus recommended that women with previous GDM breastfeed, although it was acknowledged that data to demonstrate efficacy were lacking.57 In 2007, the Fifth International Workshop-Conference made the same recommendation and stated the need for research on breastfeeding’s effects on health of GDM offspring.58 Identification of modifiable risk factors in early life that prevent childhood obesity is important among GDM offspring because they are more likely to become overweight, and develop impaired glucose tolerance, the metabolic syndrome, and type 2 diabetes.8–13
Prospective studies of women with a history of GDM and their offspring are needed to gather evidence related to breastfeeding and infant growth, as well as development of diabetes, controlling for parental attributes, intrauterine metabolic milieu, maternal postpartum glucose tolerance, and postnatal behavioral traits. Further research is needed to determine whether favorable effects of lactation persist years after delivery to influence development of type 2 diabetes in women. Specifically, biochemical measurements from before to after pregnancy may provide important clues to mechanisms related to lactation’s influence on type 2 diabetes in women beyond the childbearing years. Breastfeeding is a modifiable health behavior that may play an important role in future disease risk for women with a history of GDM and their offspring.
Acknowledgments
Supported by Career Development Award, Grant number K01 DK059944 from the National Institute of Diabetes, Digestive and Kidney Diseases, R01 HD050625 from the National Institute of Child Health and Human Development, and a Clinical Research Award from the American Diabetes Association.
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