Women with gestational diabetes mellitus (GDM) continue to face challenges in initiating breastfeeding despite its many benefits (1). Neonatal intensive care unit/special care nursery (NICU/SCN) admission is particularly associated with reduced breastfeeding uptake (2). In the recent Treatment of Booking Gestational Diabetes Mellitus (TOBOGM) randomized controlled trial (RCT), early diagnosis and immediate management of GDM control (deferred treatment) decreased the risk of adverse neonatal outcomes by 1.2–10.1% and reduced NICU/SCN duration of stay (3). It is unclear whether early diagnosis and treatment of GDM influences breastfeeding uptake. We have now compared breastfeeding initiation as the first step toward longer-term breastfeeding within the TOBOGM cohort. The RCT study design was reported previously (3). The protocol was approved by local ethics committees in each country commencing with South-Western Sydney Local Health District Research and Ethics Office, Australia (15/LPOOL/551). Uptake of breastfeeding as the first feeding method was the primary outcome in this secondary analysis. We also compared, within the complete TOBOGM recruitment cohort, breastfeeding initiation in women with early treated GDM (eGDM) (from <20 weeks’ gestation), GDM treated from 24–28 weeks’ gestation (lGDM), and those with no GDM (noGDM). For the cohort study, women in the TOBOGM RCT randomized to the control (deferred treatment) group but no GDM at 24–28 weeks’ gestation were allocated to the noGDM group. Women with overt diabetes in pregnancy were excluded. At all study institutions, breastfeeding is strongly advocated to all pregnant women, with and without GDM. Adjusted odds ratios (AORs) were estimated for two outcomes (breastfeeding as the first feeding method [irrespective of subsequent feeding] and initiation of breastfeeding within 1 h of birth) using multivariable logistic regression models adjusted for maternal characteristics (hospital, age, education, ethnicity, current smoking, parity, and prepregnancy BMI). Birth and neonatal characteristics (gestation at time of birth, birth weight, neonatal sex, birth method, NICU/SCN admission, and neonatal hypoglycemia [defined as heelprick glucose <2.2 mmol/L (40 mg/dL) within 2 h performed in those with GDM] and a random selection of others [3]) were then added stepwise to ascertain their impact on between-group differences in both the RCT and in the complete TOBOGM recruitment cohort. Model 5 is the fully adjusted model. Statistical analyses were conducted using IBM SPSS Statistics (version 29).
Overall, 3,323 (85.9%) participants with available breastfeeding data were included. Their mean age was 31.3 ± 5.1 years, mean prepregnancy BMI 28.9 ± 7.5 kg/m2, 41.5% were of European descent, and their first clinic visit was at 14 ± 3 weeks’ gestation. Individuals without breastfeeding data were similar in terms of these characteristics besides being 0.6 years older and more likely to be South Asian.
With regard to breastfeeding outcomes by randomization group, the unadjusted breastfeeding initiation rates were 297 or 357 (83.2%) in the early treatment group and 279 or 355 (78.6%) in the deferred treatment group. The AOR for not breastfeeding initially in the deferred treatment group was 0.64 (95% CI 0.42–0.98) after adjusting for maternal characteristics and 0.68 (95% CI 0.40–1.16) after adjusting for birth and neonatal characteristics. There was no difference in breastfeeding initiation within 1 h (overall, 254 of 572 [44.4%]; AOR 1.01 [95% CI 0.71–1.45]).
We also conducted secondary analysis of breastfeeding outcome in the complete cohort. Unadjusted breastfeeding initiation prevalence decreased across groups from noGDM (1,806 of 2,031; 88.9%) to treated eGDM (314 of 381; 82.4%) to lGDM (503 of 630; 79.8%) groups (P < 0.001). While neonatal sex was similar across the three groups, gestational age (38.8 ± 1.6 vs. 38.2 ± 1.8 vs. 38.3 ± 1.6 weeks, respectively; P < 0.001) and birth weight (3.4 ± 0.7 vs. 3.3 ± 0.7 vs. 3.3 ± 0.6 kg, respectively, P < 0.001) were highest in the noGDM group. After adjusting for potential confounders (see Table 1 for multivariable analysis models), compared with the noGDM group (reference = 1), the AOR among women in the eGDM group was 0.96 (95% CI 0.66–1.38), but it was significantly less (AOR, 0.62; 95% CI 0.47–0.83) among women in the lGDM group. Adding neonatal hypoglycemia (where measures were available; n = 963) to the analysis did not change the AOR. After excluding preterm babies (<37 weeks’ gestation) as a sensitivity analysis, the model 5 AORs were 0.79 (95% CI 0.54–1.16) for women in the eGDM group and 0.54 (95% CI 0.40–0.73) for women in the lGDM group. Initiation of breastfeeding within 1 h was not different between groups: 74.6% in the noGDM group, 62.2% in the eGDM group, and 65.9% in the lGDM group (P = 0.235). In the multivariable model, no association was found between eGDM or lGDM and initiating breastfeeding within 1 h of birth.
Multivariable association between GDM groups and breastfeeding outcomes (first feeding method and initiation of breastfeeding within 1 h)
| Cohort and GDM group | Model 1 | Model 2 | Model 3 | Model 4 | Model 5 | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| AOR (95% CI) | P value | AOR (95% CI) | P value | AOR (95% CI) | P value | AOR (95% CI) | P value | AOR (95% CI) | P value | ||
| First feeding method (breastfed vs. not) | |||||||||||
| eGDM | 0.62 (0.45, 0.86) | 0.003 | 0.70 (0.50, 0.97) | 0.034 | 0.78 (0.56, 1.10) | 0.157 | 0.81 (0.57, 1.14) | 0.226 | 0.96 (0.66, 1.38) | 0.807 | |
| lGDM | 0.48 (0.37, 0.62) | <0.001 | 0.50 (0.38, 0.64) | <0.001 | 0.57 (0.43, 0.75) | <0.001 | 0.57 (0.43, 0.74) | <0.001 | 0.62 (0.47, 0.83) | 0.001 | |
| noGDM | Ref | Ref | Ref | Ref | Ref | Ref | Ref | Ref | Ref | Ref | |
| Initiation of breastfeeding within 1 h | |||||||||||
| eGDM | 0.94 (0.73, 1.22) | 0.645 | 0.96 (0.73, 1.25) | 0.752 | 1.05 (0.80, 1.38) | 0.711 | 1.07 (0.81, 1.42) | 0.622 | 1.14 (0.86, 1.51) | 0.379 | |
| lGDM | 0.88 (0.71, 1.09) | 0.235 | 0.91 (0.72, 1.13) | 0.383 | 0.97 (0.78, 1.22) | 0.815 | 0.98 (0.78, 1.24) | 0.888 | 1.03 (0.81, 1.3) | 0.810 | |
| noGDM | Ref | Ref | Ref | Ref | Ref | Ref | Ref | Ref | Ref | Ref | |
| Cohort and GDM group | Model 1 | Model 2 | Model 3 | Model 4 | Model 5 | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| AOR (95% CI) | P value | AOR (95% CI) | P value | AOR (95% CI) | P value | AOR (95% CI) | P value | AOR (95% CI) | P value | ||
| First feeding method (breastfed vs. not) | |||||||||||
| eGDM | 0.62 (0.45, 0.86) | 0.003 | 0.70 (0.50, 0.97) | 0.034 | 0.78 (0.56, 1.10) | 0.157 | 0.81 (0.57, 1.14) | 0.226 | 0.96 (0.66, 1.38) | 0.807 | |
| lGDM | 0.48 (0.37, 0.62) | <0.001 | 0.50 (0.38, 0.64) | <0.001 | 0.57 (0.43, 0.75) | <0.001 | 0.57 (0.43, 0.74) | <0.001 | 0.62 (0.47, 0.83) | 0.001 | |
| noGDM | Ref | Ref | Ref | Ref | Ref | Ref | Ref | Ref | Ref | Ref | |
| Initiation of breastfeeding within 1 h | |||||||||||
| eGDM | 0.94 (0.73, 1.22) | 0.645 | 0.96 (0.73, 1.25) | 0.752 | 1.05 (0.80, 1.38) | 0.711 | 1.07 (0.81, 1.42) | 0.622 | 1.14 (0.86, 1.51) | 0.379 | |
| lGDM | 0.88 (0.71, 1.09) | 0.235 | 0.91 (0.72, 1.13) | 0.383 | 0.97 (0.78, 1.22) | 0.815 | 0.98 (0.78, 1.24) | 0.888 | 1.03 (0.81, 1.3) | 0.810 | |
| noGDM | Ref | Ref | Ref | Ref | Ref | Ref | Ref | Ref | Ref | Ref | |
Model 1 was adjusted for hospital, age, qualification, ethnicity, current smoking, and parity. Model 2 is model 1 plus pregrenancy BMI. Model 3 is model 2 plus gestation at time of birth, birth weight, and neonatal sex. Model 4 is model 3 plus birth method. Model 5 is model 4 plus NICU/SCN admission (neonatal hypoglycemia was run within a separate analysis due to lower numbers of babies having a heelprick). In the RCT, the unadjusted breastfeeding initiation rates were 297/357 (83.2%) in the early treatment group and 279/355 (78.6%) in the deferred treatment group. The AOR for not breastfeeding initially in the deferred treatment group was 0.64 (95%CI 0.42–0.98) after adjusting for maternal characteristics (model 2) and 0.68 (95%CI 0.40–1.16) after adjusting for birth and neonatal characteristics (model 5). Ref, reference value.
After adjusting for maternal factors, uptake of breastfeeding as the first feeding method was lower in those with GDM diagnosed later in both our RCT of deferred (vs. early) GDM treatment and in our cohort study comparing GDM diagnosed later or earlier with controls. After adding neonatal factors to the model, the association was attenuated to null in the RCT but not the cohort study. This association with late diagnosis and treatment of GDM could not be explained by higher NICU/SCN admission, as this was adjusted for in the cohort multivariable analysis. One possible mechanism is that earlier improvement in metabolic management in the eGDM group corresponded to an early critical gestational time point in the physiological preparation for lactation that includes breast remodeling and maturation. The difference in breastfeeding initiation between the two GDM groups also could be explained by a longer duration and more frequent interactions with the antenatal care team (including education by a midwife and/or lactation consultant) for women with eGDM, providing more opportunities to reinforce messages about the benefits of breastfeeding (4). While prepregnancy maternal overweight or obesity has previously been shown to be independently associated with breastfeeding outcomes in the long-term (5), the comparisons included adjustment for BMI.
This study is not without limitations, as breastfeeding data were collected only for the period before discharge from hospital, and breastfeeding initiation does not have the strength of association with breastfeeding outcomes, such as exclusive breastfeeding to hospital discharge. Breastfeeding intention, other social determinants of health, and measures of glycemia achieved were also not available. Further research is required to understand the impact of early diagnosis and immediate treatment of GDM on longer-term breastfeeding and long-term metabolic outcomes in the mothers and their offspring.
Clinical trial reg. no. ACTRN12616000924459, www.anzctr.org.au.
*A complete list of TOBOGM Research Group Members can be found in the appendix.
This article is part of a special article collection available at https://diabetesjournals.org/collection/2624/TOBOGM-Collection.
Article Information
Acknowledgments. We would like to thank the study participants involved in TOBOGM, the trial coordinators, research midwives, and nurses at each site; the maternity service and laboratory staff who assisted the project; the trial coordination staff; and the personnel at Roche for the donation of the glucose-monitoring meters used for the trial participants. We thank Professor Anand Hardikar for conceptualizing, drawing, and revising the graphical abstract.
Funding. This study is supported by the National Health and Medical Research Council (grants 1104231 and 2009326), the Region Örebro Research Committee (grants Dnr OLL-970566 and OLL-942177), the Medical Scientific Fund of the Mayor of Vienna (projects 15205 and 23026), the South Western Sydney Local Health District Academic Unit (grant 2016), and a Western Sydney University Ainsworth Trust Grant (2019).
Neither the funding sources nor the author-affiliated institutions took part in the trial design, the collection, analysis, and interpretation of the data, manuscript writing, or the decision to submit it for publication.
Duality of Interest. No potential conflicts of interest relevant to this article were reported.
Author Contributions. D.S. conceived the project and C.N.S. drafted the paper. J.I. assisted with the initial paper draft. All authors contributed to the writing and reviewed and edited the manuscript. All authors approved the final version of the manuscript. D.S. is the guarantor of this work and, as such, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Prior Presentation. Parts of this study were presented in poster form at the Australasian Diabetes in Pregnancy Society Annual Scientific Meeting, Adelaide, Australia, 25–27 August 2023.
Handling Editors. The journal editors responsible for overseeing the review of the manuscript were Steven E. Kahn and Camille E. Powe.
Appendix
Members of the TOBOGM Research Group include David Simmons (Western Sydney University, Campbelltown, New South Wales, Australia), N. Wah Cheung (Westmead Hospital, Sydney, New South Wales, Australia), Jincy Immanuel (Western Sydney University, Campbelltown, New South Wales, Australia), William M. Hague (Robinson Research Institute, The University of Adelaide, Adelaide, South Australia, Australia), Helena Teede (Monash Health and Monash University, Melbourne, Victoria, Australia), Christopher J. Nolan (Canberra Hospital and Australian National University, Canberra, Australian Capital Territory, Australia), Michael J. Peek (Australian National University, Canberra, Australian Capital Territory, Australia), Jeff R. Flack (Bankstown-Lidcombe Hospital, Sydney, New South Wales, Australia), Mark McLean (Blacktown Hospital, Sydney, New South Wales, Australia), Vincent Wong (Liverpool Hospital, Sydney, New South Wales, Australia), Emily Hibbert (Nepean Clinical School, University of Sydney and Nepean Hospital, Sydney, New South Wales, Australia), Emily Gianatti (Department of Endocrinology, Fiona Stanley Hospital, Murdoch, Western Australia, Australia), Arianne Sweeting (Department of Endocrinology, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia), Suzette Coat (Robinson Research Institute, The University of Adelaide, Adelaide, South Australia, Australia), Raiyomand Dalal (Campbelltown Hospital, Campbelltown, New South Wales, Australia), Georgia Soldatos (Monash Health and Monash University, Melbourne, Victoria, Australia), Suja Padmanabhan (Westmead Hospital, Sydney, New South Wales, Australia), Rohit Rajagopal (Campbelltown Hospital, Campbelltown, New South Wales, Australia), Victoria Rudland (Westmead Hospital, Sydney, New South Wales, Australia), Jürgen Harreiter (Gender Medicine Unit, Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria), Alexandra Kautzky-Willer (Gender Medicine Unit, Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria), Herbert Kiss (Division of Feto-Maternal Medicine, Department of Obstetrics and Gynecology, Medical University of Vienna, Vienna, Austria), Helena Backman (Department of Obstetrics and Gynecology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden), Erik Schwarcz (Department of Internal Medicine, Faculty of Medicine and Health, Örebro University, Örebro, Sweden), Glynis Ross (Royal Prince Alfred Hospital, Sydney, New South Wales, Australia), Viswanathan Mohan (Dr. Mohan’s Diabetes Specialities Centre and Madras Diabetes Research Foundation, Chennai, India), Ranjit Mohan Anjana (Dr. Mohan’s Diabetes Specialities Centre and Madras Diabetes Research Foundation, Chennai, India), and Uma Ram (Seethapathy Clinic & Hospital, Chennai, India).
