Table 1.
The characteristics of the 18 included studies, mean ± SD
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Ref.
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Study design
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Study period
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Population
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Age of all patients (years)
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Sample size, (n)
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Breastfeeding duration
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Follow-up period
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Disease reported: Diabetes or hypertension
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Data of outcomes (OR/HR)
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Adjustment factors
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| Adam et al[36] (2021), Sudan | Case-control study | May-December 2019 | Women with preeclampsia + healthy controls | Median (range) cases: 33.0 (28.0-38.0), controls: 30.0 (25.0-33.0) | 348 | Yes/No | N/A | Hypertension | Adjusted OR = 0.31 (95%CI: 0.15-0.67) | Age, parity, education level, occupation, history of preeclampsia, history of miscarriage, and BMI |
| Bajaj et al[37] (2017), Canada | Prospective observational cohort study | Not specified | Women recruited from antepartum GDM screening | ≤ 3 months lactation: 34 ± 4, 3-12 months lactation: 35 ± 4, ≥ 12 months lactation: 35 ± 4 | 330 | Breastfed for ≤ 3 months (n = 70), for 3–12 months (n = 140), and for ≥ 12 months (n = 120) | 3 years | Diabetes | Lactation for ≥ 6 months: OR = 0.49 (95%CI: 0.24-1.00); Lactation for ≥12 months: OR = 0.37 (95%CI: 0.18–0.78) | Age, ethnicity, family history of diabetes, GDM, and physical activity |
| Blair et al[38] (2024), United States | Secondary analysis | July 2016-July 2018 | Women with recent Gestational Diabetes Mellitus | Not breastfeeding: 31.5 ± 5.7, Breastfeeding: 33.7 ± 5.0 | 178 | Yes/No | 8 weeks | Hypertension | Adjusted OR = 0.56 (95%CI: 0.19-1.60) | Age, race/ethnicity, low household income, pre-pregnancy BMI, and weeks since delivery |
| Gunderson et al[22] (2015), United States | Prospective observational study | August 2008-December 2011 | Women diagnosed with GDM | Exclusive formula: 33.0 ± 4.9, mostly formula: 33.4 ± 5.0, mostly breastfeeding: 33.4 ± 4.8, exclusively breastfeeding: 33.5 ± 4.4 | 1035 | Yes/No | 2 years | Diabetes | Adjusted HR = 0.53 (95%CI: 0.36-0.77) | Selected groups of baselines, perinatal, and newborn covariates |
| Gunderson et al[39] (2018), United States | Prospective observational cohort study | 1986-2016 | Women without diabetes before pregnancy who delivered an infant after baseline | Incident diabetes: 24.2 ± 3.7, no diabetes: 24.0 ± 3.7 | 1238 | Time-dependent lactation duration categories (none, > 0 to 6 months, > 6 to < 12 months, and ≥ 12 months) | 30 years | Diabetes | Pool adjusted HR = 0.63 (95%CI: 0.48-0.83) | Examination years (time), race, family history of diabetes, baseline age, fasting glucose, BMI and waist circumference, time dependent GDM, party, physical activity, and dietary quality score |
| Jäger et al[27] (2014), Germany | Prospective observational cohort study | 1994-1998 | Women who gave birth | Median (interquartile range) No breastfeeding: 47 ± 15, < 3 weeks of breastfeeding: 46 ± 15, 3 weeks-2 months of breastfeeding: 47 ± 16.5, 2-6 months, 47 ± 17, 6+ months: 49 ± 19 | 1059 | Duration and Yes/No | Not specified. | Diabetes | Adjusted HR = 0.77 (95%CI: 0.47-1.25) | Age, marital status, education, occupation, smoking behavior, etc. |
| Kim et al[40] (2016), Korea | Cross-sectional | Not specified | Women who gave birth | 39.9 (SD not specified) | 1053 | Yes/No | N/A | Hypertension | Adjusted OR = 0.63 (95%CI: 0.36-1.08) | The first childbirth age, the last childbirth age, gravidity, natural childbirth, and cesarean section |
| Ley et al[29] (2020), United States | Prospective cohort study | 1989-2014 | Female registered nurses with a history of GDM | Median age 31.8 (95%CI: 25.2–40.2) | 4372 | Duration: No breastfeed, 1, 1-3, 4-6, 7-11, 12-17, 18-23, 23-35, 36-47, ≥ 48 months, and cannot remember | 87,411 person-years of follow-up | Diabetes | Pool adjusted HR = 1 (95%CI: 0.96-1.04) for lactation | Age, parity, primipara, pre-pregnancy BMI, and age at index GDM diagnosis |
| Luo et al[41] (2019), United States | Prospective cohort study | 1993-1998 | Postmenopausal women | Nulliparous: 62.4 ± 7.8, 1-4 parities: 62.8 ± 7.3, 5+ parities: 64.7 ± 6.2 | 136652 | Duration: No breastfeed, 1-6, 7-12, 13-23, and ≥ 24 months | 14.2 years | Diabetes | Adjusted HR = 0.88 (95%CI: 0.78-0.99) for < 6-month lactation; adjusted HR = 0.96 (95%CI: 0.92-1.01) for 6 to 12 months’ lactation | Age, race and ethnicity, level of education, BMI, waist circumference, physical activity, smoking, alcohol intake, family history of diabetes, history of hormone therapy use, and age at menopause, etc. |
| Martens et al[42] (2016) Canada | Retrospective cohort study | 1987-2011 | Women who gave birth in Manitoba | 27.74 ± 5.55 | 180107 | Yes/No | Up to 24 years | Diabetes | Adjusted HR = 0.73 (95%CI: 0.68-0.79) | Age at birth of child, sex, residence, parity, ethnicity, and income |
| Mazariegos et al[43] (2019), Mexico | Prospective cohort study | 2006–2008 | Female teachers who are 25 years old and older | 0 months: 47.4 ± 6.9, < 3 months: 46.2 ± 7.3, 3-6 months: 45.7 ± 7.2, 6-12 months: 45.0 ± 7.2, > 12 months: 44.4 ± 7.3) | 66573 | Duration: No breastfeed, 1-6, 7-12, and 13-24 months | 157,510 person years of follow-up | Diabetes | Adjusted HR = 0.71 (95%CI: 0.60-0.84) for < 6-month lactation; adjusted HR = 0.81 (95%CI: 0.68-0.97) for 6 to 12 months’ lactation | Age, age at first birth, age at menarche, smoking, diet, physical activity, educational level, socio-economic status, and marital status |
| Pettitt et al[44] (1997), United States | Prospective cohort study | 1950-1978 | Women who gave birth | 23-65 | 720 | Yes/No | Not specified. | Diabetes | Adjusted OR = 0.41 (95%CI: 0.17-0.98) | Age, birth year (police related), sex, parental diabetes, relative weight, birthweight |
| Ra et al[47] (2020), Korea | Cross-sectional | 2004-2016 | Postmenopausal women older than 40 years | > 40 years | 1983 | Duration and Yes/No | N/A | Hypertension | Adjusted OR = 1.23 (95%CI: 0.81-1.86) | Age, family history, BMI, age of menarche, socioeconomic status, alcohol consumption, and smoking |
| Ram et al[48] (2008), United Kingdom | Longitudinal observational study | 1995–1997 | Midlife women transitioning through menopause | 46.4 ± 2.7 | 2516 | Yes/No | Not specified. | Hypertension | Adjusted OR = 0.83 (95%CI: 0.68-0.998) | Age, physical activity, daily caloric intake, high school BMI, parity, socioeconomic status, study site, current smoking, and ethnicity |
| Schwarz et al[46] (2009), United States | Prospective observational study | Began in 1994 | Postmenopausal women | Range: 50-79 | 139681 | Duration: No breastfeed, 1-6, 7-12, and 13-23, and ≥ 24 months | Mean = 35 years | Hypertension and diabetes | Hypertension: Adjusted HR = 0.87 (95%CI: 0.82-0.93) for 6 to 12 months’ lactation; Diabetes: Adjusted HR = 0.69 (95%CI: 0.58-0.84) for 6 to 12 months’ lactation | Age, race, parity, age at menopause, education, income, family history (of diabetes mellitus, myocardial infarction or stroke), physical activity, energy, cholesterol, fat, fiber, and sodium intakes, tobacco history, hormone replacement therapy use, aspirin use, and multivitamin use |
| Stuebe et al[49] (2006), United States | Prospective cohort study | 1989-2001 | Female registered nurses | Range: 25-55 | 83585 | Duration: No breastfeed, 1-3, > 3-6, > 6-11, > 11-23, 13-23, and > 23 months | 1,239,709 person-years of follow-up | Diabetes | Adjusted HR = 0.73 (95%CI: 0.54-0.99) for < 6-month lactation; adjusted HR = 0.62 (95%CI: 0.48-0.81) for 6 to 12 months’ lactation | Age, parity, BMI at 18 years, Dietary score quintile, physical activity, family history of diabetes, smoking status, birth weight of participants, and multivitamin use |
| Shen et al[50] (2019), China | Prospective observational study | 1999-2008 | Women diagnosed with GDM | Not specified | 1260 | Duration | Mean = 3.65 years | Diabetes | Adjusted HR = 0.7 (95%CI: 0.4-1.22) for < 6-month lactation; adjusted HR = 0.34 (95%CI: 0.19-0.6) for 6 to 12 months’ lactation | Pregnant age, education, family income, family history of diabetes, treatment of GDM, smoking, passive smoking, alcohol drinking, leisure-time physical activity, sleeping time, dietary fiber, sweetened beverage drinking, energy intakes of fat, protein, carbohydrate, and prepregnancy, BMI, and 2-hour glucose during pregnancy |
| Ziegler et al[45] (2012), Germany | Prospective observational study | 1989-1999 | Women diagnosed with GDM | Not specified | 304 | Yes/No | From delivery for up to 19 years | Diabetes | Adjusted HR = 0.54 (95%CI: 0.34-0.85) | Diabetes treatment during pregnancy, BMI, and duration of breastfeeding |
HR: Hazard ratio; OR: Odds ratio; BMI: Body mass index; DIE: Deep infiltrative endometriosis; GDM: Gestational diabetes mellitus; IVF: In vitro fertilization.