Childhood follow-up of the GRoW randomized trial: Metformin in addition to dietary and lifestyle advice for pregnant women with overweight or obesity

Long-term effects of metformin on offspring health: A review of current evidence and future directions

Metformin is widely prescribed for the management of type 2 diabetes mellitus, polycystic ovary syndrome, and gestational diabetes mellitus in pregnancy. Its use is driven by factors including oral administration, lower patient and health system burden and cost, and benefits including lower risk of excess gestational weight gain and hypoglycemia compared with insulin. Metformin use appears safe in pregnancy; however, there remain concerns regarding long-term effects of intrauterine metformin exposure on offspring health. Randomized controlled trial follow-up studies suggest that metformin-exposed offspring may have altered postnatal growth trajectories and increased adiposity in childhood, although data are limited. Whether this is a transient adaptation or a precursor to long-term metabolic dysfunction is unclear, as data on cardiometabolic and neurodevelopmental parameters, including glucose homeostasis, lipid metabolism, and cognitive function, are sparse and inconsistent. Methodological challenges include heterogeneous study designs, high attrition rates, and inadequate control for confounding variables. Given these uncertainties, further well-powered, long-term prospective studies and individual patient data meta-analyses, harmonizing data and adjusting for confounders, are needed to clarify risks and benefits of metformin use in pregnancy. Until such data are available, clinicians must weigh the benefits and advantages of metformin use in pregnancy against the unknowns regarding potential long-term impact on offspring health. PLAIN LANGUAGE SUMMARY: Metformin is a medicine often used during pregnancy to help manage conditions such as type 2 diabetes, gestational diabetes, and polycystic ovary syndrome (PCOS). It is commonly chosen because it is taken as a tablet rather than by injection, has a lower risk of causing low blood sugar, and is generally easier and less expensive to use than insulin. Research has shown that metformin is safe for use during pregnancy in the short term. However, there are still questions about whether it has any lasting effects on children who were exposed to it before birth. This review explores this topic in detail. Some studies have found that children exposed to metformin during pregnancy may have slightly different growth patterns, such as having more body fat or being heavier in early childhood. However, these results are inconsistent and most studies show no clear differences in overall health outcomes, including in heart health, metabolism, or brain development. The results are mixed, and many studies are small or have design limitations, which makes it difficult to draw strong conclusions. At this stage, there is no clear evidence that metformin causes harm to children in the long term. However, because some studies suggest there may be effects on childhood growth and development, researchers emphasize the need for further long-term research. These future studies should follow children into adolescence and adulthood to better understand any lasting impacts. Until more is known, doctors and patients will need to carefully consider the known benefits of metformin in pregnancy alongside the current uncertainties about long-term effects on child health.

Intrauterine metformin exposure and adiposity outcomes in children: a systematic review and meta-analysis

OBJECTIVE

The study aims to assess the effect of intrauterine metformin exposure on offspring adiposity measures in childhood.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Medline, Embase and Cochrane Central were searched from inception to 4 October 2024.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Follow-up studies of randomised-controlled trials and observational studies involving metformin use in pregnancy for any insulin-resistant maternal condition were included.

DATA EXTRACTION AND SYNTHESIS

Two reviewers independently extracted data and completed risk-of-bias assessments using either Cochrane Risk-Of-Bias tool V.2 or Risk of Bias in Non-Randomised Studies of Exposure depending on study design. Meta-analyses were conducted using the generic inversed variance method in a random-effects model. Grading of Recommendations Assessment, Development and Evaluation methodology was used to assess certainty of evidence.

RESULTS

18 studies reporting on 7975 children with metformin exposure in utero and over 1 million children without metformin exposure were included. At the oldest age of follow-up reported (weighted mean age of 4.4 years), children with metformin exposure for any maternal indication had comparable body mass index (BMI) with their non-exposed peers (standardised mean difference (SMD) -0.02; 95% CI: -0.11, 0.07; low certainty). When stratified by age at follow-up, while metformin-exposed children had slightly higher BMI at 1-3 years of age (SMD 0.15; 95% CI: 0.04, 0.27; low certainty), no difference remained between the two groups by ages 3-6 and 6-11 years. When stratified by maternal diagnosis, no difference in BMI was found in the diabetes and obesity subgroups, while in the polycystic ovary syndrome subgroup metformin-exposed children were heavier than non-exposed peers (SMD 0.31; 95% CI: 0, 0.62; low certainty). No difference was seen in overweight, obesity or waist circumference.

CONCLUSIONS

Metformin-exposed children did not differ in adiposity measures compared with their non-exposed peers in later childhood. This adds to the growing body of evidence supporting the long-term safety of metformin use in pregnancy.

PROSPERO REGISTRATION NUMBER

CRD42023394464.

Is metformin safe in pregnancy: a focus on offspring outcomes

INTRODUCTION

Metformin has been part of treatment algorithms for type 2 diabetes mellitus (T2DM) for decades. While it has formal approval in the U.S.A. for treatment of T2DM, it is used off-label in gestational diabetes mellitus (GDM), polycystic ovarian syndrome (PCOS), and ovarian hyperstimulation prevention. Its role as an insulin sensitizer has made it an attractive therapeutic to address the insulin resistance seen in these syndromes. In 2022, the European Union approved metformin as the only oral antidiabetic medication for diabetes in pregnancy. While its safety and benefits for the mother are well documented, it does cross the placenta with plasma concentrations comparable between mother and child at delivery.

AREAS COVERED

This special report will focus on major randomized control trials investigating metformin use in pregnancies impacted by PCOS, GDM, T2DM, and obesity and their offspring follow-up trials.

EXPERT OPINION

For the mother, metformin can be beneficial, with reduction in insulin therapeutic burden, weight gain, hypoglycemia and in certain situations, pre-eclampsia. For the neonate, benefits may include reduction in hypoglycemia and no increased risk of congenital anomalies. It is the long-term data in the offspring that remains unknown with some areas of concerns (SGA, altered anthropometrics) requiring continued research.

Metformin in pregnancy and childhood neurodevelopmental outcomes: a systematic review and meta-analysis

OBJECTIVE

This study aimed to examine the impact of maternal metformin use during pregnancy on offspring neurodevelopmental outcomes.

DATA SOURCES

MEDLINE, Embase, and Web of Science (Core Collection) were searched from inception until July 1, 2023.

STUDY ELIGIBILITY CRITERIA

Studies of women who received treatment with metformin at any stage of pregnancy for any indication with neurodevelopmental data available for their offspring were included. Studies without a control group were excluded. Randomized controlled trials, case-control, cohort, and cross-sectional studies were included in the review.

METHODS

Studies were screened for inclusion and data were extracted independently by 2 reviewers. Risk of bias was assessed using a modified version of the Newcastle-Ottawa Scale for nonrandomized studies, and the Risk of Bias 2 tool for randomized trials.

RESULTS

A total of 7 studies met the inclusion criteria, including a combined cohort of 14,042 children with 7641 children who were exposed and followed for up to 14 years of age. Metformin use during pregnancy was not associated with neurodevelopmental delay in infancy (relative risk, 1.09; 95% confidence interval, 0.54-2.17; 3 studies; 9668 children) or at ages 3 to 5 years (relative risk, 0.90; 95% confidence interval, 0.56-1.45; 2 studies; 6118 children). When compared with unexposed peers, metformin use during pregnancy was not associated with altered motor scores (mean difference, 0.30; 95% confidence interval, -1.15 to 1.74; 3 studies; 714 children) or cognitive scores (mean difference, -0.45; 95% confidence interval, -1.45 to 0.55; 4 studies; 734 children). Studies that were included were of high quality and deemed to be at low risk of bias.

CONCLUSION

In utero exposure to metformin does not seem to be associated with adverse neurodevelopmental outcomes in children up to the age of 14 years. These findings provide reassurance to clinicians and pregnant women considering metformin use during pregnancy.

The role of the placenta-brain axis in psychoneuroimmune programming

Gestational exposures have enduring impacts on brain and neuroimmune development and function. Perturbations of pregnancy leading to placental structure/function deficits, cell stress, immune activation, and endocrine changes (metabolic, growth factors, etc.) all increase neuropsychiatric risk in offspring. The existing literature links obstetric diseases with placental involvement to offspring neuroimmune outcomes and neurodevelopmental risk. Psychoneuroimmune outcomes in offspring brain include changes to microglia, cytokine/chemokine production, cell stress, and long-term immunoreactivity. These outcomes are altered by structural, anti-angiogenic/hypoxic, inflammatory, and metabolic diseases of the placenta. This fetal programming occurs via direct placental passage or production of factors which can act directly on fetal brain substrates, or indirectly via action of circulating factors on intermediates in the placenta. Placental neuroendocrine, vascular/angiogenic, immune, and extracellular vesicular mechanisms are detailed. These mechanisms interact within various placental and pregnancy conditions. An increased understanding of the placental origins of psychoneuroimmunology will yield dividends for human health. Identifying maternal and placental biomarkers for fetal neuroimmune health may also revolutionize early diagnosis and precision psychiatry, empowering patients to make the best healthcare decisions for their families. Targeting placental mechanisms may be a valuable approach for the prevention and mitigation of intergenerational, lifelong neuropathology.

Position paper of the Italian Association of Medical Diabetologists (AMD), Italian Society of Diabetology (SID), and the Italian Study Group of Diabetes in pregnancy: Metformin use in pregnancy

OBJECTIVE

This document purpose is to create an evidence-based position statement on the role of metformin therapy in pregnancy complicated by obesity, gestational diabetes (GDM), type 2 diabetes mellitus (T2DM), polycystic ovary syndrome (PCOS) and in women undergoing assisted reproductive technology (ART).

METHODS

A comprehensive review of international diabetes guidelines and a search of medical literature was performed to identify studies presenting data on the use of metformin in pregnancy. The document was approved by the councils of the two scientific societies.

RESULTS

In condition affecting the fertility, as PCOS, metformin use in pre-conception or early in pregnancy may be beneficial for clinical pregnancy, even in ART treatment, and in obese-PCOS women may reduce preterm delivery. In obese women, even in the presence of GDM or T2DM, metformin use in pregnancy is associated with a lower gestational weight gain. In pregnancy complicated by diabetes (GDM or T2DM), metformin improves maternal glycemic control and may reduce insulin dose. Neonatal and infant outcomes related to metformin exposure in utero are lacking. Metformin use in women with GDM or T2DM is associated with lower birth weight. However, an increased tendency to overweight-obesity has been observed in children, later in life.

CONCLUSIONS

Metformin may represent a therapeutic option in selected women with obesity, PCOS, GDM, T2DM, and in women undergoing ART. However, more research is required specifically on the long-term effects of in utero exposition to metformin.

Focus on Metformin: Its Role and Safety in Pregnancy and Beyond

Metformin is used worldwide in the treatment of type 2 diabetes and has been used in the treatment of diabetes in pregnancy since the 1970s. It is highly acceptable to patients due to its ease of administration, cost and adverse effect profile. It is effective in reducing macrosomia, large-for-gestational-age infants and reduces maternal weight gain. Despite its many advantages, metformin has been associated with reductions in foetal size and has been associated with an increase in infants born small-for-gestational-age in certain cohorts. In this article, we review its efficacy, adverse effects and long-term follow-up before, during and after pregnancy for both mother and infant. We also evaluate the other forms of treatment for gestational diabetes, including oral therapies, insulin therapy and emerging treatments.