Point: Oral hypoglycemic agents should not be used to treat diabetic pregnant women

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

INTRODUCTION

Gestational diabetes mellitus (GDM) is a common disorder of pregnancy and contributes to adverse pregnancy outcomes. Metformin is often used for the prevention and management of GDM; however, its use in pregnancy continues to be debated. The Metformin in Pregnancy Study aims to use individual patient data (IPD) meta-analysis to clarify the efficacy and safety of metformin use in pregnancy and to identify relevant knowledge gaps.

METHODS AND ANALYSIS

MEDLINE, EMBASE and all Evidence-Based Medicine will be systematically searched for randomised controlled trials (RCT) testing the efficacy of metformin compared with placebo, usual care or other interventions in pregnant women. Two independent reviewers will assess eligibility using prespecified criteria and will conduct data extraction and quality appraisal of eligible studies. Authors of included trials will be contacted and asked to contribute IPD. Primary outcomes include maternal glycaemic parameters and GDM, as well as neonatal hypoglycaemia, anthropometry and gestational age at delivery. Other adverse maternal, birth and neonatal outcomes will be assessed as secondary outcomes. IPD from these RCTs will be harmonised and a two-step meta-analytic approach will be used to determine the efficacy and safety of metformin in pregnancy, with a priori adjustment for covariates and subgroups to examine effect moderators of treatment outcomes. Sensitivity analyses will assess heterogeneity, risk of bias and the impact of trials which have not provided IPD.

ETHICS AND DISSEMINATION

All IPD will be deidentified and studies contributing IPD will have ethical approval from their respective local ethics committees. This study will provide robust evidence regarding the efficacy and safety of metformin use in pregnancy, and may identify subgroups of patients who may benefit most from this treatment modality. Findings will be published in peer-reviewed journals and disseminated at scientific meetings, providing much needed evidence to inform clinical and public health actions in this area.

Metformin treatment of type 2 diabetes mellitus in pregnancy: update on safety and efficacy

With the increasing prevalence of type 2 diabetes mellitus (T2DM) in women of childbearing age, prescribing antidiabetic medications in first-trimester pregnancy is becoming more common. Metformin treatment during this time is usually avoided in countries with well-resourced healthcare. This is based on historical concerns about safety to the foetus and the widespread availability of insulin. However, there is now increasing interest in the potential benefits of metformin in pregnant women with T2DM. In this commentary, the main evidence supporting metformin safety in pregnancy is summarized, with an emphasis on the first trimester. Based on a structured literature search, the recent randomized controlled trials comparing metformin and insulin are reviewed. We then show that prescribing advice for metformin in pregnancy is inconsistent and product information/package inserts (PI) are universally out of date. This causes confusion and pushes some women and their clinicians to change from metformin to insulin. The potential advantages of metformin in pregnant women with T2DM are then discussed, including oral dosing and improved acceptability, lower resource utilization and cost, decreased insulin requirements, less maternal weight gain and less risk of maternal and neonatal hypoglycaemia. The conclusion is that metformin is a cheap and efficacious antidiabetic medication for many pregnant women with T2DM, with reasonable evidence for safety. Drug information resources should be updated so that metformin can be considered more broadly in women with T2DM who present for antenatal care.

Oral anti-diabetic agents for women with established diabetes/impaired glucose tolerance or previous gestational diabetes planning pregnancy, or pregnant women with pre-existing diabetes

BACKGROUND

While most guidance recommends the use of insulin in women whose pregnancies are affected by pre-existing diabetes, oral anti-diabetic agents may be more acceptable to women. The effects of these oral anti-diabetic agents on maternal and infant health outcomes need to be established in pregnant women with pre-existing diabetes or impaired glucose tolerance, as well as in women with previous gestational diabetes mellitus preconceptionally or during a subsequent pregnancy. This review is an update of a review that was first published in 2010.

OBJECTIVES

To investigate the effects of oral anti-diabetic agents in women with established diabetes, impaired glucose tolerance or previous gestational diabetes who are planning a pregnancy, or pregnant women with pre-existing diabetes, on maternal and infant health. The use of oral anti-diabetic agents for the management of gestational diabetes in a current pregnancy is evaluated in a separate Cochrane Review.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 October 2016) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs assessing the effects of oral anti-diabetic agents in women with established diabetes, impaired glucose tolerance or previous gestational diabetes who were planning a pregnancy, or pregnant women with pre-existing diabetes. Cluster-RCTs were eligible for inclusion, but none were identified.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility, extracted data and assessed the risk of bias of the included RCTs. Review authors checked the data for accuracy, and assessed the quality of the evidence using the GRADE approach.

MAIN RESULTS

We identified six RCTs (707 women), eligible for inclusion in this updated review, however, three RCTs had mixed populations (that is, they included pregnant women with gestational diabetes) and did not report data separately for the relevant subset of women for this review. Therefore we have only included outcome data from three RCTs; data were available for 241 women and their infants. The three RCTs all compared an oral anti-diabetic agent (metformin) with insulin. The women in the RCTs that contributed data had type 2 diabetes diagnosed before or during their pregnancy. Overall, the RCTs were judged to be at varying risk of bias. We assessed the quality of the evidence for selected important outcomes using GRADE; the evidence was low- or very low-quality, due to downgrading because of design limitations (risk of bias) and imprecise effect estimates (for many outcomes only one or two RCTs contributed data).For our primary outcomes there was no clear difference between metformin and insulin groups for pre-eclampsia (risk ratio (RR) 0.63, 95% confidence interval (CI) 0.33 to 1.20; RCTs = 2; participants = 227; very low-quality evidence) although in one RCT women receiving metformin were less likely to have pregnancy-induced hypertension (RR 0.58, 95% CI 0.37 to 0.91; RCTs = 1; participants = 206; low-quality evidence). Women receiving metformin were less likely to have a caesarean section compared with those receiving insulin (RR 0.73, 95% CI 0.61 to 0.88; RCTs = 3; participants = 241; low-quality evidence). In one RCT there was no clear difference between groups for large-for-gestational-age infants (RR 1.12, 95% CI 0.73 to 1.72; RCTs = 1; participants = 206; very low-quality evidence). There were no perinatal deaths in two RCTs (very low-quality evidence). Neonatal mortality or morbidity composite outcome and childhood/adulthood neurosensory disability were not reported.For other secondary outcomes we assessed using GRADE, there were no clear differences between metformin and insulin groups for induction of labour (RR 1.42, 95% CI 0.62 to 3.28; RCTs = 2; participants = 35; very low-quality evidence), though infant hypoglycaemia was reduced in the metformin group (RR 0.34, 95% CI 0.18 to 0.62; RCTs = 3; infants = 241; very low-quality evidence). Perineal trauma, maternal postnatal depression and postnatal weight retention, and childhood/adulthood adiposity and diabetes were not reported.

AUTHORS' CONCLUSIONS

There are insufficient RCT data to evaluate the use of oral anti-diabetic agents in women with established diabetes, impaired glucose tolerance or previous gestational diabetes who are planning a pregnancy, or in pregnant women with pre-existing diabetes. Low to very low-quality evidence suggests possible reductions in pregnancy-induced hypertension, caesarean section birth and neonatal hypoglycaemia with metformin compared with insulin for women with type 2 diabetes diagnosed before or during their pregnancy, and no clear differences in pre-eclampsia, induction of labour and babies that are large-for-gestational age. Further high-quality RCTs that compare any combination of oral anti-diabetic agent, insulin and dietary and lifestyle advice for these women are needed. Future RCTs could be powered to evaluate effects on short- and long-term clinical outcomes; such RCTs could attempt to collect and report on the standard outcomes suggested in this review. We have identified three ongoing studies and four are awaiting classification. We will consider these when this review is updated.

Comparison of glyburide with metformin in treating gestational diabetes mellitus: a systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

Controversy has surrounded the treatment of gestational diabetes mellitus (GDM) for a long time. Although the use of both glyburide and metformin are recommended as an alternate to insulin if dietary therapy fails in GDM patients, it remains unclear whether both drugs are equally safe and efficacious. Therefore, in this review we compared the efficacy and safety of glyburide with metformin in treating GDM.

METHODS

A systematic review and meta-analysis of randomized controlled trials was conducted that compared the efficacy and safety of glyburide with metformin in GDM patients. Electronic databases were used to conduct the literature search for study identification along with a hand search of pertinent journals and conference proceedings. The effect measure used to present the results was risk ratio (RR) with 95% confidence interval (CI). A fixed-effects model was used to pool the data if no significant heterogeneity was reported and a random-effects model was used in the case of significant heterogeneity being reported for an outcome.

RESULTS

Three studies involving 508 patients met the inclusion criteria of this review. A significant increase in the risk of the composite outcome, i.e., macrosomia and large for gestational age (LGA) births (RR 1.94; 95% CI 1.03-3.66, p = 0.04), was observed in the glyburide group, whereas a non-significant increase in the risk of neonatal hypoglycemia (RR 1.92; 95% CI 0.31-12.02) was also noticed. Results remained statistically non-significant for preterm births (RR 0.65; 95% CI 0.24-1.77), neonatal birth weight (mean difference (MD) 120.63 g; 95% CI -62.08 to 303.33), and cesarean section (RR 0.86; 95% CI 0.55-1.34). A significant decrease in fasting glucose levels (MD -2.40 mg/dL; 95% CI -4.60 to -0.21; p = 0.03) was noticed in glyburide group while the difference was non-significant for postprandial glucose levels (MD -0.84 mg/dL; 95% CI -4.03 to 2.35).

CONCLUSION

Metformin seems to be a superior choice to glyburide if oral antidiabetic drug therapy is to be initiated in GDM patients.

Safety considerations with pharmacological treatment of gestational diabetes mellitus

The number of women with gestational diabetes mellitus (GDM: diabetes first diagnosed in pregnancy) continues to grow, as do the associated risks of antenatal and postnatal complications and the chance of future diabetes and obesity in both mother and offspring. Recent randomised controlled trials have demonstrated clear benefits for intensive management of GDM using lifestyle modification, self blood glucose monitoring, close clinical supervision and, where glycaemia remains inadequately controlled, insulin therapy. More recently, metformin and glibenclamide have been shown to adequately reduce hyperglycaemia as part of a stepped approach to GDM management, with a switch to insulin therapy where necessary. Other oral medications have not been shown to be safe in pregnancy. Human insulin therapy is safe within the limits of hypoglycaemia and weight gain. Most insulin analogues are also now considered safe for use in pregnancy (insulin lispro, aspart and detemir). Metformin therapy is oral, and therefore preferred to insulin, but is associated with more gastrointestinal adverse effects, although not hypoglycaemia or weight gain. Conversely, glibenclamide is also an oral therapy but is associated with hypoglycaemia and weight gain. However, metformin crosses the placenta and it remains unclear whether glibenclamide crosses the placenta or not: long-term risks have not been shown, and are thought to be minimal, but further studies are needed. Metformin is seen by some as the treatment of choice where weight gain is an issue, providing that the unanswered questions over the long-term safety of oral agents have been discussed.

Recent advances in the diagnosis and management of gestational diabetes

Gestational diabetes is a condition which is seen in 7% of pregnancies and have potential risks for both mother and fetus. Despite its importance, there is not any golden standard approaches to the diagnosis and management of the disease. The aim of this review was to investigate the advances in the diagnosis and management of gestational diabetes in recent years.

Prevalence of diagnosed and undiagnosed type 2 diabetes mellitus among US adolescents: results from the continuous NHANES, 1999-2010

Although prevalence and incidence of type 2 diabetes mellitus (T2DM) are reportedly increasing among adolescents, national data are lacking, particularly in regard to undiagnosed T2DM. To estimate the prevalence of diagnosed and undiagnosed T2DM among US adolescents, we analyzed a nationally representative cross-section of 11,888 adolescents aged 12-19 years who received a diabetes interview in the Continuous National Health and Nutrition Examination Survey during 1999-2010. Among them, a random subsample of 4,661 adolescents also had fasting blood samples collected. Persons who reported a previous diabetes diagnosis and were either taking no medication or taking an oral hypoglycemic agent (with or without insulin) were classified as having T2DM; persons who reported using insulin alone were classified as having type 1 diabetes. Undiagnosed diabetes was defined as a fasting plasma glucose concentration of ≥126 mg/dL and was assumed to be type 2. In the fasting subsample, 31 diabetes cases (types 1 and 2) were identified, representing a prevalence of 0.84% (weighted 95% confidence interval (CI): 0.51, 1.40) (276,638 cases; 95% CI: 134,255, 419,020). Estimates of the prevalences of type 1 and type 2 diabetes were 0.48% (95% CI: 0.23, 1.02) and 0.36% (95% CI: 0.20, 0.67), respectively, indicating that T2DM accounted for 43% of all cases. Further, undiagnosed T2DM prevalence was 0.12% (95% CI: 0.05, 0.31), representing 34% of T2DM cases (40,611 cases; 95% CI: 2,850, 78,373). T2DM accounts for approximately half of adolescent diabetes in the United States, and one-third of these cases are undiagnosed.

Oral anti-diabetic agents for women with pre-existing diabetes mellitus/impaired glucose tolerance or previous gestational diabetes mellitus

BACKGROUND

While most guidelines recommend the use of insulin in women whose pregnancies are affected by pre-existing diabetes, oral agents have obvious benefits for patient acceptability and adherence. It is necessary, however, to assess the effects of these anti-diabetic agents on maternal and infant health outcomes. Additionally, women with previous gestational diabetes mellitus are increasingly found to be predisposed to impaired glucose tolerance and, despite the potential need for intervention for these women, there has been little evidence about the use of oral anti-diabetic agents by these women pre-conceptionally or during a subsequent pregnancy.

OBJECTIVES

To investigate the effect of oral anti-diabetic agents in women with pre-existing diabetes mellitus, impaired glucose tolerance or previous gestational diabetes planning a pregnancy or pregnant women with diabetes mellitus on maternal and infant health.The use of oral antidiabetic agents for management of gestational diabetes in a current pregnancy is evaluated in a separate Cochrane review.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (March 2010).

SELECTION CRITERIA

We included randomised and quasi-randomised trials.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial eligibility for inclusion.

MAIN RESULTS

We identified 13 trials published as 25 papers using the Cochrane Pregnancy and Childbirth group literature search, and an additional ongoing trial. We have not included any trials in the review. One trial is awaiting assessment and we have excluded twelve trials because they evaluated treatment of women with gestational diabetes or women with polycystic ovary syndrome, were not randomised controlled trials or data were not available.

AUTHORS' CONCLUSIONS

Little randomised evidence is available evaluating the use of oral anti-diabetic agents in women with diabetes mellitus, impaired glucose tolerance, previous gestational diabetes mellitus planning a pregnancy or pregnant women with pre-existing diabetes mellitus. Large trials comparing any combination of oral anti-diabetic agent, insulin and dietary and lifestyle advice in these women, reporting on maternal and infant health outcomes, glycaemic control, women's views on the intervention and long-term health outcomes for mother and child, are required to guide clinical practice.

Technology and pregnancy

In the USA, depending upon the diagnosis criteria used, 135,000-200,000 women annually develop gestational diabetes mellitus, adding to the number of pregnant women already suffering from either type 1 or type 2 diabetes. Maternal hyperglycaemia and the resultant fetal hyperinsulinaemia are central to the pathophysiology of diabetic complications of pregnancy. These complications include congenital malformations and an increase in neonatal intensive care unit admission and birth trauma. In addition, there is an increased rate of accelerated fetal growth, neonatal metabolic complications and risk for stillbirth. Importantly, during the last century there were two breakthroughs in diabetes management and monitoring that changed the course of treatment: the discovery of insulin and the progress in the understanding of glucose monitoring. As technology has evolved, both glucose monitoring and insulin administration can now be achieved in a continuous fashion. In this review of the literature we focus on the utility of new technologies in the management and monitoring of diabetes in pregnancy.

Metformin treatment for Type 2 diabetes in pregnancy?

Metformin lowers blood glucose by reducing hepatic glucose output, increasing insulin sensitivity and enhancing peripheral glucose uptake. Metformin is widely used in women with Type 2 diabetes of child-bearing age, many of whom become pregnant. Studies to date in Type 2 diabetes in pregnancy, gestational diabetes and polycystic ovarian syndrome are reassuring. Metformin is not considered teratogenic. There is sufficient evidence that metformin is safe used throughout pregnancy, with no worsening of obstetric or perinatal outcomes. Women may benefit from the lesser weight gain. The long-term risks to the offspring remain inadequately researched, with no evidence of harm up to 2 years, and no suggestions of later complications in countries using metformin for many years. Metformin is recommended for use in pregnancies complicated by Type 2 diabetes, but women should be informed of the evidence regarding its associated risks and benefits to enable an informed choice over its use.

Approach to the patient with diabetes during pregnancy

The epidemics of obesity and type 2 diabetes mellitus (T2DM) globally are paralleling an increase in the number of women with T2DM becoming pregnant. Because T2DM is frequently undiagnosed before pregnancy, the risk of major malformations in the developing fetus is increased due to uncontrolled hyperglycemia. The lack of preconception care and the increase in complications of pregnancy due to the coexistence of obesity and T2DM are of concern from both an individual and a public health standpoint. Rapid achievement of normoglycemia with limited weight gain is critical to optimize maternal and fetal outcomes in all women with diabetes during pregnancy, regardless of the type of diabetes. This article will focus on T2DM preceding pregnancy due to its increasing prevalence and potentially dire fetal and maternal consequences. Euglycemia before, during, and after all pregnancies complicated by diabetes results in the best opportunity for optimal outcomes for mother and infant.

Factors predicting the need for insulin therapy in patients with gestational diabetes mellitus

AIM

To determine the possible factors predicting the insulin requirement in pregnancies complicated by gestational diabetes mellitus (GDM).

METHOD

A total of 294 patients with GDM diagnosed by the 100-g/3-h oral glucose tolerance test (OGTT) were studied. The following factors were analyzed: maternal age, nulliparity, family history of diabetes, prepregnancy BMI, prior GDM, prior fetal macrosomia, multiple pregnancy, polyhydramnios, gestational age at diagnosis of GDM, smoking, hypertension, number of abnormal 100-g/3-h OGTT values, and glycated hemoglobin (HbA1c). The association between each factor and the need for insulin therapy was then analyzed individually. The performance of these factors to predict the probability of insulin therapy was estimated using a logistic regression model.

RESULTS

Univariate analysis showed a positive correlation between insulin therapy and prepregnancy BMI, family history of diabetes, hypertension, prior GDM, prior fetal macrosomia, number of abnormal 100-g/3-h OGTT values, and HbA1c (P<0.05). Prepregnancy BMI, family history of diabetes, number of abnormal 100-g/3-h OGTT values and HbA1c were statistically significant variables in the logistic regression model.

CONCLUSIONS

The probability of insulin therapy can be estimated in pregnant women with GDM based on prepregnancy BMI, family history of diabetes, number of abnormal 100-g/3-h OGTT values, and HbA1c concentration.