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Management of Diabetes Mellitus by Obstetrician–Gynecologists

Gabbe, Steven G., MD*; Gregory, Rebecca Pratt, MS, RD; Power, Michael L., PhD; Williams, Sterling B., MD§; Schulkin, Jay, PhD§

doi: 10.1097/01.AOG.0000128045.50439.89
Original Research

OBJECTIVE: To compare practice patterns of the American College of Obstetrician and Gynecologists (ACOG) Fellows for the diagnosis and treatment of gestational diabetes mellitus (GDM) and type 1 diabetes mellitus with current ACOG recommendations and prior published series.

METHODS: We sent a questionnaire to 1,398 practicing ACOG Fellows and Junior Fellows, 398 of whom comprise the Collaborative Ambulatory Research Network. Responses were evaluated by age and sex to assess differences in practice.

RESULTS: Younger physicians were more likely to treat pregnant patients. Ninety-six percent of obstetricians routinely screen for GDM, nearly all by using a 50-g glucose 1-hour oral test. Nearly 60% of respondents establish the diagnosis of GDM using the National Diabetes Data Group criteria. In addition to medical nutrition therapy, almost 75% of respondents recommend exercise for patients with GDM. Approximately 60% of respondents reported that all of their patients with GDM self-monitor their blood glucose. When medical nutrition therapy is ineffective for their patients with GDM, 82% of respondents initially prescribe insulin, whereas 13% begin with glyburide. Nearly 75% of respondents routinely perform a postpartum evaluation of glucose tolerance in the patient with GDM. Most obstetricians manage the glucose control of their patients with type 1 diabetes mellitus themselves.

CONCLUSION: Practicing obstetrician–gynecologists have incorporated recent recommendations into their practice patterns for both GDM and type 1 diabetes mellitus, including patients’ self-monitoring of blood glucose, exercise, and postpartum testing in GDM.


During the past 16 years, the American College of Obstetricians and Gynecologists Fellows have become increasingly more responsible for managing glucose levels in pregnancies complicated by gestational and type 1 diabetes mellitus.

From the *Vanderbilt University School of Medicine, †Department of Obstetrics and Gynecology, Vanderbilt University School of Medicine; and ‡Vanderbilt Diabetes Center, Vanderbilt University School of Medicine, Nashville, Tennessee; and §Department of Research, American College of Obstetricians and Gynecologists, Washington, DC.

Supported by the Health Resources and Services Administration–Maternal and Child Health Bureau.

Reprints are not available. Address correspondence to: Steven G. Gabbe, MD, Vanderbilt University Medical Center, D-3300 Medical Center North, Nashville, TN 37232–2104; e-mail:

Received December 19, 2003. Received in revised form March 4, 2004. Accepted March 11, 2004.

The strategies and techniques for the management of diabetes mellitus during pregnancy have improved greatly during the past 2 decades. New insulin therapies are now available, and the self-monitoring of blood glucose by patients with diabetes is widely incorporated in care plans. As a result of these advances, the incidence of perinatal morbidity and mortality has been greatly reduced.1 Obstetrician–gynecologists routinely treat patients with type 1, type 2, and gestational diabetes mellitus (GDM). In this study, we sought to compare the practice patterns of American College of Obstetricians and Gynecologists (ACOG) Fellows and Junior Fellows with current ACOG recommendations. We asked about screening methods, criteria for diagnosis, the use of self-monitoring of blood glucose in their patients, preferred medications, and how other health care providers assist in caring for pregnant patients with diabetes. We also compared these data to practice patterns documented during the past 16 years in prior series.2,3

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Surveys were mailed to 1,398 ACOG Fellows and Junior Fellows in practice, 398 of whom comprise the Collaborative Ambulatory Research Network. Network Fellows are practicing obstetrician–gynecologists who voluntarily participate in survey studies. The Network was established to facilitate the assessment of patterns in obstetric and gynecologic clinical practice and to help in the development of professional education. The 1,000 non-Network Fellows were randomly chosen by computer from ACOG Fellows and Junior Fellows who are practicing obstetrics and/or gynecology and have not been previously selected as a part of a Network study. A second mailing was sent 6 weeks later to encourage nonrespondents in the non-Network Fellows group to participate. On the basis of 5 years of experience, we expected this protocol to result in approximately equal numbers of respondents in the 2 groups and to produce a total sample size of greater than 450. This expected sample size is sufficient to detect differences between groups of less than one half of one standard deviation with a power of 80% and significance at the .05 level; the 95% confidence interval for binomially distributed responses will be less than 5%.

The survey consisted of questions concerning physician and patient demographics; clinical practice, including screening and diagnostic methods; treatment of diabetes mellitus during pregnancy; and physician self-assessment of medical training. The survey instrument used and the procedures for the selection of Network and non-Network Fellows were similar to our 2 earlier studies.2,3

Data were analyzed by using a personal computer–based software package (SPSS 11.0; SPSS Inc, Chicago, IL). Descriptive statistics were computed for the measures used in the analyses, which are reported as mean ± standard error of the mean. Two-tailed t tests were applied to compare group means of age. Group differences of continuous measures were assessed by using analysis of covariance, with Network status and sex as categorical variables and age as the covariate. Differences in categorical measures were assessed by using χ2. Correlations among ordinal measures were assessed by using the Spearman rank correlation test. All analyses were tested for significance by using α < .05.

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Of the 1,398 mailed surveys, 6 were found to be undeliverable (4 Network and 2 random Fellows), and 569 surveys were returned by Fellows (246 Network and 323 random Fellows). The response rate for Network Fellows was 62.4% and for non-Network Fellows 32.4%, for an overall response rate of 40.9%. The second mailing to non-Network Fellows yielded 72 responses. Respondents came from all 10 ACOG districts, from all 50 states, and from the District of Columbia. Of the 569 total respondents, 128 (44 Network and 84 random Fellows) reported they did not treat pregnant patients, leaving 441 surveys (202 Network, 239 random Fellows) for analysis. There was no difference in age or sex between Fellows that did or did not return surveys (P = .196 and P = .132, respectively; Table 1).

Table 1

Table 1

For both male and female respondents, those who treated pregnant patients were, on average, younger than those who did not. Men were less likely to treat pregnant patients (43 of 248, 17.3%) than women (85 of 321, 26.5%; P = .01). However, that finding is probably explained by the fact that the women who returned surveys were, on average, younger than men (42.5 ± 0.5 years versus 51.0 ± 0.5 years, respectively P < .001).

Membership in the Network was not a significant factor in any of the analyses. Accordingly, the responses from Network Fellows and random Fellows were combined and reported in aggregate.

Studies previously conducted have shown that routine screening for GDM is a common practice.2,3 Our survey revealed that universal testing of pregnant women for GDM was performed by 96% (421 of 441) of obstetricians. Of those who screen their patients, 95.2% (420 of 441) used a 50-g glucose 1-hour oral test.

The 2 most common diagnostic criteria for the diagnosis of GDM are the Carpenter and Coustan revised criteria, recently recommended by the American Diabetes Association (ADA), and the National Diabetes Data Group criteria, each having a different level of sensitivity (Table 2). 4–6 The Carpenter and Coustan criteria were used by 37.9% (167 of 441) and the National Diabetes Data Group criteria by 59% (260 of 441) of respondents. After the diagnosis of GDM, 32.2% (142 of 441) ordered further laboratory work, including a glycosylated hemoglobin level (n = 99), renal function studies and a 24-hour urine collection (n = 18), and thyroid function studies (n = 17).

Table 2

Table 2

The management of GDM by respondents included medical nutrition therapy, exercise, the oral hypoglycemic drug glyburide, and insulin. Medical nutrition therapy is the foundation for the initial treatment of GDM.6,7 Our data suggest that respondents often refer patients to others for the medical nutrition therapy portion of care. The assistance of a registered dietitian or diabetes nurse educator is used by 68.9% (304 of 441) and 58.3% (257 of 441) of respondents, respectively, whereas 27.9% (123 of 441) of the obstetrician–gynecologists performed the medical nutrition therapy education themselves. Of those who do refer to a registered dietitian, the medical nutrition therapy/diet prescription is determined by the registered dietitian in 68.9% (304 of 441) of cases and by the obstetrician in 29.7% (131 of 441) of cases. When asked who participated in the management of glucose control once therapy was initiated, respondents reported the obstetrician in 71.2% (314 of 441) of patients, the diabetes nurse educator in 37.6% (166 of 441), a maternal–fetal medicine specialist in 26.1% (115 of 441), a diabetes specialist in 22% (97 of 441), a registered dietitian in 25.4% (112 of 441), and an office nurse in 8.6% (38 of 441). Exercise is used in addition to medical nutrition therapy by 73.9% (325 of 441) of respondents. Of these, most (229 of 325, 70.5%) recommend walking. More than 80% (274 of 325) of obstetrician–gynecologists recommending exercise provided an advised frequency. Of the 274 respondents, 56.2% recommend daily exercise, and 38.3% support exercise 3– 5 days per week. The modal recommendation (127 of 325, 39.1%) was daily walking.

When medical nutrition therapy alone does not achieve the desired results, respondents turned to insulin or glyburide. Our data revealed that 82.3% (363 of 441) of obstetrician–gynecologists used insulin first, whereas 13.2% (58 of 441) begin with glyburide.

Self-monitoring of blood glucose is used widely in the management of GDM.8,9 Nearly 60% (244 of 422, 57.9%) of respondents reported that all of their patients use self-monitoring of blood glucose whereas 82% (362 of 441) noted that at least 75% of their patients did (Table 3). Of those who recommend their patients self-monitor their blood glucose, 90.7% (400 of 441) of obstetricians request that their patients measure their fasting glucose level, whereas 61.2% (270 of 441) recommend 2-hour postprandial tests. Four tests per day are ordered by 63% (278 of 441) of obstetrician–gynecologists, and 12.6% (33 of 416) ask that 5–8 tests be performed daily. The targets for blood glucose results were fasting mean 97.3 mg/dL, standard deviation (SD) 3.2 (n = 409); preprandial mean 103.6 mg/dL, SD 12.4 (n = 124); 1-hour postprandial mean 134.6 mg/dL, SD 15.5 (n = 219); 2-hour postprandial mean 122.1 mg/dL, SD 11.2 (n = 324).

Table 3

Table 3

Self-monitoring of blood glucose results are used in the following manner: in 88.4% (390 of 441) of cases to determine whether the patient needs insulin or glyburide; in 79.8% (352 of 441) of cases to make changes in prescribed medications, and in 63.7% (281 of 441) to change a patient’s medical nutrition therapy. Testing for urinary ketones was recommended by 30.2% (133 of 441) of the obstetricians surveyed, and of these, 35.3% (47 of 133) advise that it be performed daily.

Respondents (80.3%, 354 of 441) use antepartum fetal monitoring in patients with GDM (Table 3). Of the methods used to evaluate fetal well-being, the nonstress test was most widely applied (327 of 441, 74.1%), followed by the biophysical profile (108 of 441, 24.5%), amniotic fluid index (44 of 441, 10%), and ultrasound assessment of fetal growth (32 of 441, 7.3%). Most clinicians use the nonstress test weekly (187 of 327, 57.5%) or twice weekly (114 of 327, 34.9%). Physicians initiate fetal monitoring at an average of 35.7 (range 26–41) weeks of gestation for diet-controlled patients and at 32.2 (range 29–39) weeks of gestation for patients on insulin or glyburide.

Approximately 74% (329 of 441) of obstetricians routinely perform a postpartum evaluation of glucose tolerance in the patient diagnosed with GDM (Table 3). A 75-gram, 2-hour oral glucose tolerance test is used by 50.8% (167 of 329) and a fasting glucose by 27.4% (90 of 329). Physicians younger than 40 years of age were more likely to routinely perform a postpartum evaluation (87.6% versus 73.2%; P = .005).

Half of the respondents (220 of 441, 49.9%) considered their training during residency regarding GDM to have been comprehensive, and a further 41% (182 of 441) considered it adequate. Most respondents were very confident of their ability to diagnose (307 of 441, 69.6%) and manage (251 of 441, 56.9%) GDM. Physicians younger than 40 years were more likely to rate their residency education as comprehensive (P < .001) and to be more confident in their ability to diagnose and manage GDM (P < .001). Self-assessment of training and confidence regarding diagnosis and management of GDM were in concordance (r = .497 and r = .488, P < .001, in both cases).

The care of type 1 diabetes mellitus during pregnancy is more complex than that of GDM. In these patients, 54.9% (242 of 441) of respondents manage glucose control themselves. However, a diabetes specialist, such as an endocrinologist, participates in this care in 34.5% (152 of 441) of patients, a maternal–fetal specialist in 34.5% (152 of 441), a diabetes nurse educator in 16.1% (71 of 441), a registered dietitian in 10.2% (45 of 441), and an office nurse in 5.4% (24 of 441).

Self-monitoring of blood glucose is widely used in the pregnant patient with type 1 diabetes mellitus. Ninety percent of obstetricians request a fasting glucose determination, 56.9% (251 of 441) a 2-hour postprandial value, 31.1% (137 of 441) a 1-hour postprandial test, and 28% (123 of 441) preprandial values, and 6.8% (30 of 441) check random glucose levels.

The variety of insulin now available has increased the therapeutic options for the obstetrician–gynecologist who manages the patient with the type 1 diabetes mellitus. We found that 75.3% (332 of 441) use regular insulin and 42% (185 of 441) insulin lispro. For long-acting insulin, 75.5% (333 of 441) use NPH or Lente insulin (Novo Nordisk Pharmaceuticals Inc, Princeton, NJ) and 13.8% (61 of 441) a 70/30 combination of NPH/regular. Only 1.6% (61 of 441) now use glargine.

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This study is the third our group has performed to compare practice patterns of obstetrician–gynecologists who care for patients with diabetes mellitus in pregnancy with present ACOG recommendations and prior published series (Table 3). In 1987, we surveyed 273 members of the Society for Maternal–Fetal Medicine who, at that time, represented 65% of all those who had received certification from the American Board of Obstetrics and Gynecology in this subspecialty, and 198 Fellows of the ACOG.2 Our study in 1996 included 113 ACOG Fellows who were members of the Network and 380 randomly selected Fellows.3 That investigation evaluated not only the care of GDM but examined the likelihood that the obstetrician–gynecologist would care for women with type 1 or type 2 diabetes mellitus who were not pregnant.

Data from our present study demonstrate that obstetrician–gynecologists are following most of the recent recommendations from ACOG and the ADA in their care of patients with diabetes mellitus complicating pregnancy.6,10 We found that nearly 60% of obstetrician–gynecologists are using the National Diabetes Data Group criteria rather than the Carpenter and Coustan criteria to diagnose GDM (Table 1). The ACOG Practice Bulletin on GDM published in 2001 noted that “...there are no data from clinical trials to determine which is superior...”.10 In 2003, the ADA recommended the Carpenter and Coustan criteria.6 Although these cutoffs are lower and will therefore increase the incidence of GDM, their use will identify a population with a risk of maternal and perinatal morbidity equal to that of the National Diabetes Data Group criteria.10,11 The ADA recommendations state that a registered dietitian should provide nutrition counseling for all women diagnosed with GDM. In 68.9% of the cases, this is being performed. Nearly 75% of obstetrician–gynecologists are including exercise in addition to medical nutrition therapy in their care of patients with GDM. The American College of Obstetrician and Gynecologists has recommended that women who lead an “active lifestyle” be encouraged to continue a program of exercise that has been approved for pregnancy.10 The ADA concurs, adding that women “ encouraged to start or continue a program of moderate exercise as part of the treatment for GDM.”6 Nearly one third of obstetrician–gynecologists recommended that testing for urinary ketones be performed by their patients with GDM, and nearly one third of these practitioners prefer that it be performed daily. The American College of Obstetrician and Gynecologists notes that in women placed on a calorically restricted diet, ketonuria should be avoided. The ADA concurs, noting that “Urine ketone monitoring may be useful in detecting insufficient caloric or carbohydrate intake in women treated with calorie restriction.” Self-monitoring of blood glucose is now recommended by nearly 90% of obstetrician–gynecologists to monitor the efficacy of medical nutrition therapy and determine whether the patient will need insulin or glyburide. In using self-monitoring of blood glucose, obstetrician–gynecologists are recommending targets for glucose control consistent with those of both ACOG and the ADA, that is, fasting glucose values of 95 mg/dL, 1-hour postprandial values of 130–140 mg/dL, and 2-hour postprandial values of 120 mg/dL.6,10 When diet and exercise do not provide satisfactory glucose control, more than 80% of obstetrician–gynecologists use insulin. Only 13.2% of respondents preferred to initiate treatment with glyburide rather than insulin in such patients. Although 1 large prospective randomized trial has found that the efficacy of glyburide is equal to that of insulin,12 obstetrician–gynecologists appear to be following the recommendations of both ACOG and ADA that additional clinical studies are needed before the use of glyburide can be advised in pregnancy.6,10

Comparison of the data collected in 1987, 1996, and the present investigation reveals several important changes in the practice patterns of obstetrician–gynecologists (Table 3). In 1987, although nearly 90% of maternal–fetal medicine specialists screened all of their patients for GDM, 76.7% (152 of 198) of ACOG Fellows followed this practice.2 The 1986 ACOG Technical Bulletin on the management of diabetes mellitus in pregnancy did not recommend universal screening.13 By 1998, 96% of ACOG Fellows screened all of their patients for GDM, and this finding was again confirmed in our present study.3 In 1987, nearly all maternal–fetal medicine specialists used the 50-g glucose 1-hour test to screen for GDM compared with 83.8% (166 of 198) of ACOG Fellows.2 In the present investigation, we found that 95% of ACOG Fellows follow the recommendations of the most recent Practice Bulletin and use this method for screening. In 1987, only one third (66 of 198) of ACOG Fellows encouraged daily self-monitoring of blood glucose for their patients in the management of the GDM compared with 82.1% of maternal–fetal medicine specialists.2 This figure increased to 68% in 1998 and now exceeds 70%, again complying with the recommendations made in the most recent ACOG Practice Bulletin.3,10 That document states “...there is no consensus regarding antepartum testing in women with well-controlled GDM.” Of note, 87.4% (173 of 198) of ACOG Fellows used antepartum fetal evaluation in patients with GDM in 1987.2 That figure has declined slightly to 80.3% in the present study.

Obstetrician–gynecologists are now playing a greater role in managing glucose control in their patients with both GDM and type 1 diabetes mellitus. It is noteworthy that nearly 50% of respondents considered their residency training in GDM to be comprehensive. In 1998, 68% of ACOG Fellows reported they assumed responsibility for directing glucose control in patients with GDM.3 This figure has increased slightly to 71.2% in the present study, with a diabetes nurse educator providing assistance in 37.6% of patients. In 1987, nearly 27% (53 of 198) of ACOG Fellows managed glucose control in their patients with type 1 diabetes mellitus.2 At that same time, 82.1% of maternal–fetal medicine specialists assumed this responsibility. By 1998, 35% of ACOG Fellows were directing glucose control in patients with type 1 diabetes mellitus.3 This figure increased to nearly 55% in 2003, twice the rate observed in 1987.

American College of Obstetricians and Gynecologists Fellows appear to be more aware of the need to evaluate glucose tolerance postpartum in patients who have had GDM. In 1996, 60% performed a postpartum assessment of glucose tolerance, with 39% using the recommended 75-g, 2-hour oral glucose tolerance test.3 In the present study, nearly 75% performed a postpartum assessment of glucose tolerance, and more than half evaluated their patients with the 75-g, 2-hour oral glucose tolerance test.

Our study has demonstrated that during the past 16 years, ACOG Fellows have become increasingly comfortable managing the pregnancy complicated by GDM and type 1 diabetes mellitus. They are following the most recent recommendations in their care of these patients, including universal screening with a 50-g glucose 1-hour test, medical nutrition therapy, and exercise in the care of patients identified with GDM, and self-monitoring of blood glucose to assess the efficacy of this therapy. In addition, nearly 75% recognize the importance of postpartum assessment of glucose tolerance in their patients with GDM because these women are at higher risk of type 2 diabetes mellitus. Given that the most recent ACOG Practice Bulletin on GDM was published in 2001, our data demonstrate that ACOG Fellows are making timely changes in their practice patterns.

It must be emphasized that a potential shortcoming of our study is the possibility that “diabetes-knowledgeable” obstetricians were more likely to respond. Additional limitations of the study include the relatively low response rate of 32.4% of the randomly selected non-Network Fellows. Although membership in the Network was not a significant factor in any of the analyses, it is possible that our data may not reflect the practice patterns of a broader spectrum of ACOG Fellows.

Obstetricians have assumed greater responsibility for management of glucose control in patients with type 1 diabetes mellitus. Newer therapies for which there are limited data, such as the oral hypoglycemic agent glyburide for patients with GDM or glargine in the care of patients with type 1 diabetes mellitus, have not yet been adopted widely. As these therapies are more thoroughly investigated and other new approaches to care are introduced, it will be important to assess changes in practice patterns in the future.

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© 2004 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.