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Obstetrics
Randomized trial of metformin vs insulin in the management of gestational diabetes

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Objective

To evaluate glycemic control in women receiving metformin or insulin for gestational diabetes, and to identify factors predicting the need for supplemental insulin in women initially treated with metformin.

Study Design

Women with gestational diabetes who failed to achieve glycemic control with diet and exercise were randomized to receive metformin (n = 47) or insulin (n = 47). Criteria for inclusion were singleton pregnancy, diet, and exercise for a minimum period of 1 week without satisfactory glycemic control, absence of risk factors for lactic acidosis, and absence of anatomic and/or chromosome anomalies of the conceptus. Patients who were lost to prenatal follow-up were excluded.

Results

Comparison of mean pretreatment glucose levels showed no significant difference between groups (P = .790). After introduction of the drug, lower mean glucose levels were observed in the metformin group (P = .020), mainly because of lower levels after dinner (P = .042). Women using metformin presented less weight gain (P = .002) and a lower frequency of neonatal hypoglycemia (P = .032). Twelve women in the metformin group (26.08%) required supplemental insulin for glycemic control. Early gestational age at diagnosis (odds ratio, 0.71; 95% confidence interval, 0.52–0.97; P = .032) and mean pretreatment glucose level (odds ratio, 1.061; 95% confidence interval, 1.001–1.124; P = .046) were identified as predictors of the need for insulin.

Conclusion

Metformin was found to provide adequate glycemic control with lower mean glucose levels throughout the day, less weight gain and a lower frequency of neonatal hypoglycemia. Logistic regression analysis showed that gestational age at diagnosis and mean pretreatment glucose level were predictors of the need for supplemental insulin therapy in women initially treated with metformin.

Section snippets

Materials and Methods

Ninety-two women diagnosed with GDM, who received prenatal care at the Obstetrics Clinic of Hospital das Clinicas, Sao Paulo University School of Medicine (HC-FMUSP), Sao Paulo, Brazil, were studied prospectively between Nov. 1, 2007, and Jan 31, 2010. Criteria for inclusion were singleton pregnancy, use of diet and exercise for a minimum period of 1 week without satisfactory glycemic control, absence of risk factors for lactic acidosis (renal failure, heart failure, chronic liver disease,

Results

The initial sample consisted of 94 women who were randomized into the metformin group (group 1, n = 47) or the insulin group (group 2, n = 47). Two women were excluded for discontinuing prenatal care (1 from each group). This gave a final sample of 92 women (46 in the metformin group and 46 in the insulin group) (Figure 1).16 One of the women who presented metformin intolerance wished to discontinue the medication and human NPH was therefore introduced. For the purposes of data analysis, this

Comment

The primary objective of this study was to evaluate glycemic control in women with GDM treated with metformin or insulin. After introduction of the drugs, lower mean glucose levels were observed in the group receiving metformin (P = .020), especially after dinner (P = .042). These findings demonstrate that metformin is an effective agent for achieving glycemic control in women with GDM. In addition, weight gain between diagnosis of GDM and delivery (P = .002) and between beginning of treatment

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Clinical trial registration: Umin Clinical Trials Registry, http://www.umin.ac.jp/ctr/index.htm. UMIN 000005393.

The authors report no conflict of interest.

Cite this article as: Spaulonci CP, Bernardes LS, Trindade TC, et al. Randomized trial of metformin vs insulin in the management of gestational diabetes. Am J Obstet Gynecol 2013;209:34.e1-7.

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