Background: Segregation of the effect of maternal size and glycemia on fetal growth is difficult to understand in overweight-obese women with diabetes. Aim: To examine the effect of maternal size and degree of hyperglycemia on neonatal obesity-adiposity in the relatively thin Indian population. Study design: Analysis of real-life data collected in one diabetes clinic. Methods: We examined the association of maternal size (BMI) and degree of hyperglycemia (type of diabetes, type 1 being the thinnest and most hyperglycemic, type 2 and Gestational diabetes being overweight and obese but less hyperglycemic) with neonatal obesity-adiposity measurements (weight, ponderal index, abdominal circumference, and skinfold thickness) using multiple linear regression. Results: We included data on 772 pregnancies with diabetes (61 with type 1, 79 with type 2, and 632 with gestational) and 349 with normal glucose tolerance (NGT). Mothers with type 1 diabetes had the lowest BMI and highest HbA1c, however, their neonates were the most obese, centrally obese, and adipose. Compared to neonates of NGT mothers, those of mothers with type 1 diabetes were 370 g heavier, those of mothers with type 2 diabetes 265 g, and those of mothers with GDM by 200 g. Prediction models adjusted for gestational age at birth, neonatal sex, maternal age, parity, and year of birth confirmed that neonates of mothers with type 1 diabetes were the most obese-adipose, followed serially by those of mothers with type 2 diabetes, GDM, and NGT. Other obesity adiposity measurements showed a similar gradient. Compared to maternal type of diabetes, pre-pregnancy BMI and gestational weight gain (GWG) made a much smaller contribution to neonatal obesity-adiposity. Conclusion: Our findings provide a clear answer that maternal hyperglycemia rather than size is the primary driver of neonatal obesity-adiposity. Adequate control of maternal hyperglycemia will help control neonatal obesity-adiposity.

CSY is a visiting professor at the Danish Diabetes Academy (supported by Novo Nordisk, Denmark) and University of Southern Denmark during the conduct of the study. None of the authors declare any conflict of interest.

The study is largely intra-murally funded. The International Atomic Energy Agency, Vienna, Austria, provided financial support for the IAEA-B12 study (15382/R0). InDiaGDM study was funded by the Department of Biotechnology, New Delhi, India (BT/IN/Denmark/02/CSY/2014). Hinduja Foundation, Mumbai, Mukul Madhav Foundation, Pune and the Nityasha Foundation, Pune provide a generous grant for treatment of patients with type 1 diabetes.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Use of the real-life clinical data for research analysis was approved by King Edward Memorial Hospital Research Centre Pune, Ethics Committee, (DIP 2128/08-12- 2021). IAEA-B12 study (064/06-03-2006/15382/R0) and Indo-Danish study (BT/IN/Denmark/02/CSY/2014) also had King Edward Memorial Hospital Research Centre Ethics Committee approvals. Indo-Danish study was registered with the Clinical Trials Registry-India (NCT03388723). All participants signed an informed consent before participation.

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I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

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Prof. C.S.Yajnik 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. Data can be requested from Prof. C.S.Yajnik by applying with a 200 word plan of analysis, data sharing is subject to KEMHRC Ethics Committee approval and Govt. of India Health Ministry Screening Committee permission.