Table 1.

(Continued)

First author, year, study name, reference	T2DM definition	T2DM evaluation time	T2DM incidence among GDM women	Adjusted co‐variables for the analysis of lactation and T2DM incidence	Conclusion
Prospective cohort
Gunderson, 2015, SWIFT,26, 27, 28, 29	ADA criteria	OGTT at 1 and 2 y postpartum	113 of 959 (11.8%) developed T2DM. Overall incidence rate was 5.64 cases per 1000 person‐mo (95% CI; 4.60‐6.68).	Age; race/ethnicity; education; pre‐pregnancy BMI; GDM treatment; sum of prenatal 3‐h, 100‐g OGTT Z score; gestational age at GDM diagnosis; subsequent birth during follow‐up; total PA, GI, animal fat intake; weight change from delivery to 1 y; LGA vs not LGA, newborn's hospital stay >3 d, NICU admission	The lactation intensity and duration of breastfeeding inversely associated with T2DM incidence in a graded manner (all P < .05).
Gunderson, 2014, CARDIA,30	NG	Questionnaire at 7, 10, 15, 20, and/or 25 y after enrollment	46 of 154 (29.9%) developed T2DM. Overall incidence rate was 17.9 per 1000 person‐years.	Pre‐pregnancy BMI; age; parity; family history; race; education.	Shorter lactation (0‐1 mo vs >9 mo) was associated with higher incidence of T2DM (Adjusted RH 3.0, 95% CI; 2.1‐13.3).
Ziegler, 2012,31	ADA criteria	OGTT at 2 and 9 mo; 2, 5, 8, 11, 15, and 19 y postpartum	147 of 304 (48.4%) developed T2DM. The 15‐year cumulative risk was 63.6% (95% CI 55.8‐71.4).	Age at delivery; insulin treatment during pregnancy; BMI at early pregnancy; smoking during pregnancy; parity status; recruitment year	Longer lactation (>3 mo vs no or <3 mo) was associated with 30% risk reduction in 15‐y DM incidence (P = .0002). Full lactation duration was inversely associated with DM incidence (P = .001).
Cross‐sectional
Buchanan, 1998,32, 33	NG	OGTT within 6 mo postpartum	12 of 122 (9.8%) developed T2DM.	Not adjusted	Lactation rate 42% in DM, 49% in IGT and 71% in NGT group (P = .03)
Kim, 2011,34	ADA criteria	OGTT at 6 to 12 wk postpartum	30 of 573 (5.2%) developed T2DM.	Not adjusted	Lactation status did not affect postpartum glycemic status.
Kjos, 1993,35	NDDG criteria	OGTT at 4 to 12 wk postpartum	55 of 809 women (6.8%) developed T2DM	Not adjusted	T2DM incidence rate was 4.2% in lactating group and 9.4% in non‐lactating group (P = .01).
Urs, 2015, NHANES,36	NG	NA	NG	Age; BMI; race/ethnicity; income; education; age at DM; number of live births	Adjusted OR for incident DM after GDM (vs no GDM) was 0.6 lower in women who breastfed compared to women who did not breastfeed.
Retrospective cohort
Kjos, 1998,23, 37	NDDG criteria	OGTT within 7.5 y	Average annual incidence rate was 8.7% (non‐hormonal group).	insulin treatment during index pregnancy; glucose AUC at initial postpartum OGTT; weight change from initial postpartum weight; completion of additional pregnancy; and prior use of OC	No significant difference in T2DM risk between women who were breastfeeding vs who were not breastfeeding.
Steube, 2005, NHS II,38	Self‐report	Questionnaire up to 12 y	Incidence rate: 624 cases per 100 000 person‐years	parity, BMI at age 18 years, current BMI, dietary score quintile, PA, family history of DM, smoking status, birth weight of mother, and multivitamin use.	Lifetime lactation duration did not affect diabetes risk.

¹ Duration, evaluation of any lactation period; Initiation, evaluation of lactation experience; Intensity, evaluation of lactation or formula feeding exclusiveness; Status, evaluation of the lactation practice at the point of survey.

Abbreviations: ADA, American Diabetes Association; GI, glycemic index; IGT, impaired glucose tolerance; LGA, large for gestational age; NICU, neonatal intensive care unit; OC, oral contraceptive; NDDG, National Diabetes Data Group; OGTT, oral glucose tolerance test; OR, odds ratio; PA, physical activity; RH, relative hazards; T2DM, type 2 diabetes mellitus.