Metformin in Pregnancy Study (MiPS): protocol for a systematic review with individual patient data meta-analysis

Metformin in gestational diabetes: physiological actions and clinical applications

Metformin is an effective oral hypoglycaemic agent used in the treatment of type 2 diabetes mellitus; however, its use in pregnancy for the treatment of gestational diabetes mellitus (GDM) remains controversial owing to concerns around safety and efficacy. This comprehensive review outlines the physiological metabolic functions of metformin and synthesizes existing literature and key knowledge gaps pertaining to the use of metformin in pregnancy across various end points in women with GDM. On the basis of current evidence, metformin reduces gestational weight gain, neonatal hypoglycaemia and macrosomia and increases insulin sensitivity. However, considerable heterogeneity between existing studies and the grouping of aggregate and often inharmonious data within meta-analyses has led to disparate findings regarding the efficacy of metformin in treating hyperglycaemia in GDM. Innovative analytical approaches with stratification by individual-level characteristics (for example, obesity, ethnicity, GDM severity and so on) and treatment regimens (diagnostic criteria, treatment timing and follow-up duration) are needed to establish efficacy across a range of end points and to identify which, if any, subgroups might benefit from metformin treatment during pregnancy.

Metformin for pregnancy and beyond: the pros and cons

CONTEXT AND AIM

Metformin has been used in pregnancy since the 1970s. It is cheap, widely available and is acceptable to women. Despite its increasing use, controversy remains surrounding its benefits and risks. Metformin effectively reduces hyperglycaemia for the mother during pregnancy and it reduces rates of macrosomia and neonatal hypoglycaemia. However, concern exists surrounding an increase in the rate of SGA births and obesity in childhood. We aim to review the evidence and expert opinion behind metformin in pregnancy through to the post-partum period.

METHODS

We performed a literature review of relevant studies from online databases using a combination of keywords. We also searched the references of retrieved articles for pertinent studies.

RESULTS

There is strong evidence that metformin is safe in early pregnancy with no risk of congenital malformations. If used throughout pregnancy, it is likely to lead to reduced maternal weight gain and reduced insulin dose in women with type 2 diabetes. In infants, metformin reduces hypoglycaemia and macrosomia but may increase the rate of infants born SGA. There is some evidence of an increased risk of obesity and altered fat distribution in offspring. Metformin appears well tolerated in pregnancy and is more acceptable to women than insulin therapy.

CONCLUSION

Due to increasing rates of maternal obesity, GDM and type 2 diabetes, metformin use in pregnancy is increasing. Overall, it appears safe and effective but further research is needed to examine mechanisms linking metformin to obesity reported during childhood in some follow-up studies.

Endocrine and metabolic interactions in healthy pregnancies and hyperinsulinemic pregnancies affected by polycystic ovary syndrome, diabetes and obesity

During pregnancy, the fetoplacental unit is key in the pronounced physiological endocrine changes which support pregnancy, fetal development and survival, birth and lactation. In healthy women, pregnancy is characterized by changes in insulin sensitivity and increased maternal androgen levels. These are accompanied by a suite of mechanisms that support fetal growth, maintain glucose homeostasis and protect both mother and fetus from adverse effects of pregnancy induced insulin and androgen excess. In pregnancies affected by endocrine, metabolic disorders such as polycystic ovary syndrome (PCOS), diabetes and obesity, there is an imbalance of beneficial and adverse impacts of pregnancy induced endocrine changes. These inter-related conditions are characterized by an interplay of hyperinsulinemia and hyperandrogenism which influence fetoplacental function and are associated with adverse pregnancy outcomes including hypertensive disorders of pregnancy, macrosomia, preterm delivery and caesarean section. However, the exact underlying mechanisms and relationships of the endocrine and metabolic milieu in these disorders and the impact they have on the prenatal endocrine environment and developing fetus remain poorly understood. Here we aim to review the complex endocrine and metabolic interactions in healthy women during normal pregnancies and those in pregnancies complicated by hyperinsulinemic disorders (PCOS, diabetes and obesity). We also explore the relationships between these endocrine and metabolic differences and the fetoplacental unit, pregnancy outcomes and the developing fetus.

Metformin for gestational diabetes study: metformin vs insulin in gestational diabetes: glycemic control and obstetrical and perinatal outcomes: randomized prospective trial

BACKGROUND

Gestational diabetes that is not properly controlled with diet has been commonly treated with insulin. In recent years, several studies have published that metformin can lead to, at least, similar obstetrical and perinatal outcomes as insulin. Nevertheless, not all clinical guidelines endorse its use, and clinical practice is heterogeneous.

OBJECTIVE

This study aimed to test whether metformin could achieve the same glycemic control as insulin and similar obstetrical and perinatal results, with a good safety profile, in women with gestational diabetes that is not properly controlled with lifestyle changes.

STUDY DESIGN

The metformin for gestational diabetes study was a multicenter, open-label, parallel arms, randomized clinical trial performed at 2 hospitals in Málaga (Spain), enrolling women with gestational diabetes who needed pharmacologic treatment. Women at the age of 18 to 45 years, in the second or third trimesters of pregnancy, were randomized to receive metformin or insulin (detemir or aspart). The main outcomes were (1) glycemic control (mean glycemia, preprandial and postprandial) and hypoglycemic episodes and (2) obstetrical and perinatal outcomes and complications (hypertensive disorders, type of labor, prematurity, macrosomia, large for gestational age, neonatal care unit admissions, respiratory distress syndrome, hypoglycemia, jaundice). Outcomes were analyzed on an intention-to-treat basis.

RESULTS

Between October 2016 and June 2019, 200 women were randomized, 100 to the insulin-treated group and 100 to the metformin-treated group. Mean fasting and postprandial glycemia did not differ between groups, but postprandial glycemia was significantly better after lunch or dinner in the metformin-treated-group. Hypoglycemic episodes were significantly more common in the insulin-treated group (55.9% vs 17.7% on metformin; odds ratio, 6.118; 95% confidence interval, 3.134-11.944; P=.000). Women treated with metformin gained less weight from the enrollment to the prepartum visit (36-37 gestational weeks) (1.35±3.21 vs 3.87±3.50 kg; P=.000). Labor inductions (45.7% [metformin] vs 62.5% [insulin]; odds ratio, 0.506; 95% confidence interval, 0.283-0.903; P=.029) and cesarean deliveries (27.6% [metformin] vs 52.6% [insulin]; odds ratio, 0.345; 95% confidence interval, 0.187-0.625; P=.001) were significantly lower in the metformin-treated group. Mean birthweight, macrosomia, and large for gestational age and babies' complications were not different between treatment groups. The lower cesarean delivery rate for women treated with metformin was not associated with macrosomia, large or small for gestational age, or other complications of pregnancy.

CONCLUSION

Metformin treatment was associated with a better postprandial glycemic control than insulin for some meals, a lower risk of hypoglycemic episodes, less maternal weight gain, and a low rate of failure as an isolated treatment. Most obstetrical and perinatal outcomes were similar between groups.

Metformin for Preventing Type 2 Diabetes Mellitus in Women with a Previous Diagnosis of Gestational Diabetes: A Narrative Review

Women with a history of gestational diabetes mellitus (GDM) are at greater risk of developing type 2 diabetes mellitus (T2DM) when compared with women who have not had GDM. To delay or prevent T2DM, guidelines recommend regular screening in the primary care setting and lifestyle interventions that are largely focused on dietary and physical activity modifications. As the postpartum period can be challenging for women, uptake and engagement in screening and lifestyle interventions have been poor. Poor uptake and engagement places women with a history of GDM at heightened risk for future morbidity and development of T2DM. Metformin has been a longstanding and safe treatment for the control of blood glucose in people with T2DM. Research has supported the efficacy of metformin, used as an adjunct to a lifestyle intervention or as a stand-alone treatment, in preventing T2DM in people at high risk of T2DM. Findings from longitudinal studies have demonstrated the potential for metformin to reduce conversion to T2DM when used by women with a previous diagnosis of GDM. This review examines the potential effectiveness of metformin to reduce the incidence of T2DM among women with a previous diagnosis of GDM in the "real-world" setting.

Effects of metformin treatment on pregnancy outcomes in patients with polycystic ovary syndrome

INTRODUCTION

This review covers the current evidence regarding the use of metformin as a therapeutic intervention for optimizing pregnancy outcomes in women with polycystic ovary syndrome (PCOS).

AREAS COVERED

After searching Medline, Embase and CINAHL, all important large clinical trials and observational studies plus systematic reviews, meta-analyses and Cochrane reviews have been summarized here. The results have been compared to culminate in a thorough review and discussion on the use of metformin in relation to reproductive outcomes for women with PCOS. The role of metformin in PCOS is explored both in terms of achieving conception and during pregnancy. The existing evidence around metformin use is summarized both during the preconceptual period and during pregnancy, in relation to reproductive outcomes.

EXPERT OPINION

Metformin is a widely used medication, often prescribed to improve reproductive outcomes for women with PCOS. However, the evidence remains equivocal regarding its efficacy both in optimizing fertility and pregnancy outcomes. More research is required with special emphasis on metformin use within different populations, including ethnic groups and women with varying BMI ranges.