Treatment for Gestational Diabetes
40 Years of Research and No Consensus

Despite 4 decades of research, no consensus exists regarding screening and treatment for gestational diabetes mellitus. Several questions are still unanswered including:

• Should all pregnant women be screened or only those with risk factors?
• Are there disadvantages to screening?
• Is it safe to not screen?
• Which screening and diagnostic tests are most reliable?
• Which cutoff values should be instated?
• What are the risks involved for mother and baby?
• Can treatment improve outcomes?

Current literature reviews and meta-analyses reveal no definitive answers to these questions. No single screening test nor method has been scientifically and no threshold glucose value above which complications excessively increase has been identified. Furthermore, treatment has thus far not been shown to significantly improve outcome and the disadvantages of diagnosing and treating mothers without a a marked benefit are significant. The definition of GDM itself is controversial because blood sugar levels rise linearly as pregnancy progresses, meaning that blood sugars will and should be higher during pregnancy, making it difficult to determine appropriate threshold values.

Controversy also exists as to whether the target glucose levels to be maintained during diabetic pregnancy should be designed to limit macrosomia or to mirror nondiabetic pregnancy levels. The Fifth International Workshop Conference on Gestational Diabetes currently recommends the following:

• Fasting plasma glucose -90-99 mg/dL (5.0-5.5 mmol/L) and
• One-hour postprandial plasma glucose less than 140 mg/dL (7.8 mmol/L) or
• Two-hour postprandial plasma glucose less than 120-127 mg/dL (6.7-7.1 mmol/L)

In the US, nearly all women diagnosed with GDM, even those whose GDM is well-controlled, will have their babies by induction or planned c-section due to widespread fears over delivering a macrosomic baby (over 4000 grams or about 9 pounds) despite the lack of evidence that this clearly improves outcomes.

Glucose level in itself is a poor predictor of macrosomia. Other factors such as race, age, number of previous pregnancies, sex, and especially maternal weight, far outweigh glucose intolerance in determining birth weight.  Birth weight and glucose are only correlated in babies over the 90th percentile for weight, which typically represents mothers with Type II diabetes, not true gestational diabetes.

Late term ultrasound is also notoriously inaccurate as a measure of fetal weight.  A one-time late term ultrasound has a standard error of measure of +/- 2 pounds, which means a fetal weight estimate of 8lbs could result in a baby being born anywhere between 6-10lbs.

Weight alone is also not a reliable predictor of true cephalopelvic disproportion or which babies will experience birth injuries, suffer shoulder dystocia or require operative vaginal birth.  Too many variables factor into the equation, from head circumference and fetal position to maternal labor positions, interventions used, and pelvic dimensions.  The only way proven to determine if a baby is "too big to fit" is a trial of labor.

Options After Gestational Diabetes Diagnosis

In the majority of cases, diet and exercise are the recommended treatments, so paying special attention to these factors can lower the risks of developing complications. If diagnosed with GDM, work with a nutritionist or dietician to regulate blood sugar levels.  Sacks et al. found that women with GDM and fasting serum glucose concentrations of <=85 mg/dL to be at very low risk for perinatal complications; most likely requiring dietary management alone and no intensive monitoring or treatment.

Mothers with gestational diabetes should still be allowed to labor and birth freely in their position of choice. Maintaing adequate nutrition during labor is also essential to maintain appropriate blood sugar levels in the mother and baby.

Once the baby is born, nursing immediately will help stabilize the baby's sugar. If a blood test is suggested, it should be performed after the baby has eaten. By depriving the baby of nutrition immediately after the birth will cause hypoglycemia and may result in overtreatment of the baby that could be avoided. Also, mild asymptomatic hypoglycemia isn't typically cause for undue concern. Monitoring the baby and its feeding patterns may be recommended for the first few hours after birth.

Top of Treatment for Gestational Diabetes

References

Tieu J, Middleton P, McPhee AJ, Crowther CA. Screening and subsequent management for gestational diabetes for improving maternal and infant health. Cochrane Database of Systematic Reviews 2010, Issue 7. Art. No.: CD007222. DOI: 10.1002/14651858.CD007222.pub2

Meltzer SJ, Snyder J, Penrod JR, et al. Gestational diabetes mellitus screening and diagnosis: a prospective randomised controlled trial comparing costs of one-step and two-step methods. BJOG. Mar 2010;117(4):407-15.

Moore LE, Clokey D, Rappaport VJ, et al. Metformin compared with glyburide in gestational diabetes: a randomized controlled trial. Obstet Gynecol. Jan 2010;115(1):55-9.

Cheng YW, Chung JH, Kurbisch-Block I, et al. Gestational weight gain and gestational diabetes mellitus: perinatal outcomes. Obstet Gynecol. Nov 2008;112(5):1015-22.

Guerin A, Nisenbaum R, Ray JG. Use of maternal GHb concentration to estimate the risk of congenital anomalies in the offspring of women with prepregnancy diabetes. Diabetes Care. Jul 2007;30(7):1920-5.

Baptiste-Roberts K, Barone BB, Gary TL, et al. Risk factors for type 2 diabetes among women with gestational diabetes: a systematic review. Am J Med. Mar 2009;122(3):207-214.e4.

Sacks DA, Greenspoon JG, Abu-Fadil S, Herny HM, Wolde-Tsadik G, Yao JFF. 1995 Toward universal criteria gestational diabetes: the 75 gram glucose tolerance test in pregnancy. Am J Obstet Gynecol. 172:607-614.

Hollander MH, Paarlberg KM, Huisjes AJM. Gestational diabetes: a review of the current literature and guidelines. Obstet. Gynecol. Survey 62 (2), 125-136 (2007)

Tuffnell DJ, West J, Walkinshaw SA. Treatments for gestational diabetes and impaired glucose tolerance in pregnancy. Cochrane Database of Systematic Reviews 2003, Issue 3. Art. No.: CD003395. DOI: 10.1002/14651858.CD003395

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Giving Birth Naturally: Pregnancy Questions: Treatment for Gestational Diabetes