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Keywords:

  • Gestational diabetes;
  • postpartum care;
  • type 2 diabetes diagnosis

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure of interests
  8. Contribution to authorship
  9. Details of ethics approval
  10. Funding
  11. Acknowledgements
  12. References

Please cite this paper as: Shah B, Lipscombe L, Feig D, Lowe J. Missed opportunities for type 2 diabetes testing following gestational diabetes: a population-based cohort study. BJOG 2011;118:1484–1490.

Objectives  Few women with gestational diabetes (GDM) are tested for type 2 diabetes in the postpartum period. Whether women are having physician visits that could be an opportunity to improve testing rates is unknown. This study sought to evaluate population-level trends in postpartum diabetes testing after GDM, and to evaluate postpartum physician care for these women.

Design  Population-based cohort study.

Setting  Ontario, Canada.

Population  Women who delivered between 1994 and 2008.

Methods  Using population-level healthcare databases, we identified 47 691 women with GDM. They were matched to women without GDM.

Main outcome measures  An oral glucose tolerance test (OGTT) within 6 months postpartum, the specialty of the physician ordering the test, and ambulatory care visits with physicians from various specialties within 6 months postpartum were recorded.

Results  Most women with GDM did not receive an OGTT, although testing rates increased slowly over the 14 years of the study, compared with no change in testing for women who had not had GDM. Virtually all women with GDM had postpartum visits with a family physician or obstetrician, but few OGTTs were ordered by physicians from these specialties.

Conclusions  Despite a slow increase in testing over time and high rates of postpartum visits to family physicians and obstetricians, few women with GDM received the recommended diabetes test. This represents a missed opportunity in a high-risk population. Interventions to change test ordering that target family physicians and obstetricians are most likely to increase the proportion of women with GDM who receive postpartum diabetes testing.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure of interests
  8. Contribution to authorship
  9. Details of ethics approval
  10. Funding
  11. Acknowledgements
  12. References

Gestational diabetes mellitus (GDM) is defined as the onset or first recognition of glucose intolerance during pregnancy, and it affects about 4% of pregnant women.1,2 GDM is a potent risk factor for type 2 diabetes, which affects nearly one in five women with GDM within 9 years postpartum.1,3 The highest risk period for type 2 diabetes incidence is immediately postpartum,1 either because diabetes may persist following the GDM pregnancy, or because the GDM was actually undiagnosed type 2 diabetes that pre-dated the pregnancy but was only uncovered because of prenatal testing. As such, clinical practice guidelines in Canada recommend testing women with GDM between 6 weeks and 6 months after delivery to detect diabetes that has persisted postpartum,4–6 mirroring the recommendations in other jurisdictions. In Canada, the standard 75-g oral glucose tolerance test (OGTT) is recommended for this testing. Other tests (such as the fasting glucose) are used much more commonly for diabetes screening in the general population because they are easier to administer than the OGTT and have reasonable sensitivity in the general population.7 However, they are undesirable for diabetes case finding in high-risk postpartum young women because they are substantially less sensitive than the OGTT in this population. For example, fasting glucose detected <16% of women with postpartum glucose abnormalities.8 In addition to greater sensitivity for diagnosing diabetes, the OGTT can also identify women with lesser degrees of hyperglycaemia, in whom interventions to prevent progression to diabetes may be useful.9–11

Many previous studies have suggested that postpartum testing for type 2 diabetes remains infrequent.12–16 However, previous studies have not compared changes over time in testing rates after GDM to the baseline changes in diabetes testing in the general population. Furthermore, previous studies have not examined whether women are having postpartum ambulatory physician care at which such testing could be arranged. The aims of this study were to evaluate long-term trends in postpartum diabetes testing after GDM in comparison to trends in postpartum testing in similar women without GDM; to determine which physicians were ordering postpartum OGTTs for women after GDM; and to determine from which physicians women with GDM had postpartum ambulatory care.

Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure of interests
  8. Contribution to authorship
  9. Details of ethics approval
  10. Funding
  11. Acknowledgements
  12. References

Data sources

We conducted a retrospective population-based cohort study in the Canadian province of Ontario (population approximately 12 million), where government-funded health insurance covers hospital and physician care for all residents. The study used administrative databases that track demographic data, hospital discharge abstracts, and physician and community laboratory service claims. The laboratory service claims data included claims for reimbursement for tests, but not the results of the tests themselves. Individuals are linked between these data sources and across time using a unique health card number that is reproducibly encrypted to maintain confidentiality.

Study population

All women aged 17–49 years who had live births at an Ontario hospital between April 1994 and March 2008 were identified. Those with pre-gestational diabetes, according to a validated administrative data-derived disease registry,17 were excluded. For women with more than one birth during the study period, each birth was considered separately. Women were identified as having GDM based on the diagnoses coded on their delivery hospitalisation record. To account for secular trends in diabetes testing in the population, each woman who had GDM was matched with one woman with a live birth but without GDM. We matched on age ± 2 years, region, and quarter of delivery. Laboratory service claims were searched for an OGTT up to 6 months postpartum. In addition, laboratory claims were searched for any test that might be used to diagnose type 2 diabetes (i.e. OGTT, fasting glucose, random glucose or HbA1c) up to 6 months postpartum. Among those women who had an OGTT, the specialty of the ordering physician for the test was determined. By searching the physician service claims data, ambulatory care visits with family physicians, obstetricians and endocrinologists/internists up to 6 months postpartum for all women with GDM were identified.

Statistical analysis

We plotted the proportion of women receiving an OGTT and receiving any diabetes test by quarter for women with and without GDM. For each outcome, we built linear regression models with the quarter, the presence or absence of GDM, and an interaction between the two as the independent variables. This allowed us to determine whether testing rates were changing over time, and to compare the trend in testing among women with GDM with that among women without GDM to account for secular trends in testing. The Durbin–Watson statistic was calculated to verify the absence of autocorrelation between the observations across time.

We plotted the proportion of all women with GDM who had an OGTT by quarter, stratified by the specialty of the ordering physician of the test. We also plotted the proportion of all women with GDM who had postpartum ambulatory visits with family physicians, obstetricians and endocrinologists/internists by quarter. Women who had postpartum visits with physicians from more than one specialty were counted separately for each specialty.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure of interests
  8. Contribution to authorship
  9. Details of ethics approval
  10. Funding
  11. Acknowledgements
  12. References

There were 1 673 469 eligible births during the 14-year study period. Of them, 47 691 (2.8%) were complicated by GDM. After matching for age, region and quarter, there were 46 812 births in each cohort; the remaining 879 women with GDM (1.8%) could not be matched to a corresponding woman without GDM. The median age of women in both groups was 32 years (interquartile range, 28–35), and 8.5% of women in both groups lived in rural areas. However, women with GDM were poorer than women without GDM: 27.9% were in the lowest income group compared with 24.6%.

Figure 1A shows the proportion of women in each quarterly cohort receiving an OGTT within 6 months postpartum. As expected, postpartum OGTT for women without GDM was very uncommon, and did not change over time. Rates of postpartum testing increased by approximately 0.8% per year for women with GDM, so that the absolute proportion of women tested increased by only 11% from the beginning of the study to the end—although this represented a three-fold increase. Nonetheless, even by the end of the study period, fewer than one in six women received a postpartum OGTT.

image

Figure 1.  Postpartum diabetes testing within 6 months for women with and without gestational diabetes. (A) Oral glucose tolerance tests only. (B) Any laboratory test that might be used to diagnose diabetes.

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Figure 1B shows the proportion of women receiving any test that might be used to diagnose type 2 diabetes, including the OGTT, fasting or random glucose, or HbA1c. The increase in postpartum testing of women following GDM (0.7% per year) exceeded the secular trend of increased diabetes testing for women who had not had GDM (0.4% per year, P = 0.0001).

Figure 2 shows the proportion of all women with GDM in each quarterly cohort, stratified by the specialty of the ordering physician for the test: internists/endocrinologists, family physicians and obstetricians. (About 2% of OGTTs were ordered by physicians with other specialties; these data are not shown.) Internists/endocrinologists ordered the majority of OGTTs, with obstetricians ordering comparatively few OGTTs. Figure 3 shows the proportion of all women with GDM who had ambulatory care visits up to 6 months postpartum with physicians from these specialties. Visit rates to each type of physician remained constant throughout the 14 years of follow up. Many women with GDM had visits with family physicians or with obstetricians in the postpartum period; in fact, in each quarter throughout the study, 94–97% of women had ambulatory care visits with at least one family physician or obstetrician (data not shown). In contrast, relatively few women had visits with an internist or endocrinologist (ranging between 14 and 22% of women per quarter).

image

Figure 2.  The proportion of all women with gestational diabetes receiving a postpartum oral glucose tolerance test, stratified by the specialty of the ordering physician.

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image

Figure 3.  The proportion of all women with gestational diabetes with postpartum ambulatory care visits to physicians from various specialties.

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Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure of interests
  8. Contribution to authorship
  9. Details of ethics approval
  10. Funding
  11. Acknowledgements
  12. References

Despite increasing awareness of the high-risk that women with GDM have for developing type 2 diabetes and the importance of postpartum diabetes testing after GDM, fewer than one in six women with GDM received postpartum OGTTs at the end of the study, representing an increase of only 0.8% per year from the beginning of the study. Rates of any postpartum diabetes testing increased by 0.7% per year, which was greater than the secular trend in diabetes testing in women without GDM. Virtually all women with GDM had postpartum ambulatory care visits with a family physician or obstetrician, but only 4.5% had an OGTT ordered by one of these physicians. This missed opportunity for diabetes case finding has not been demonstrated in previous studies.

Assuming that postpartum testing would find that at least 6% of women in this population have type 2 diabetes,18 the observation that >60% received no postpartum diabetes testing translates to at least 200 missed diagnoses of diabetes annually in women of child-bearing age in Ontario. Considering that the majority of women received tests other than the OGTT that have poor sensitivity8 the number of missed cases is likely to be substantially higher. The implications of these missed diagnoses may be severe. First, these women may go on to have subsequent pregnancies with undiagnosed type 2 diabetes and potentially poor glycaemic control, increasing the risk of congenital anomalies and other fetal or maternal complications. Second, failure to identify glucose intolerance (either pre-diabetes or frank diabetes) prevents these women from implementing behavioural and medication interventions that could reduce their risk of developing diabetes or its microvascular and macrovascular complications, worsening their long-term health.

In this analysis, we have considered multiple pregnancies in the same woman separately. However, postpartum testing in this situation is probably not independent: a woman who had postpartum testing after a first GDM pregnancy is probably more likely than average to have postpartum testing if she has recurrent GDM in a subsequent pregnancy, and vice versa. There were only 4271 women with multiple GDM pregnancies in this cohort, so any bias resulting from this assumption is unlikely to be significant.

There is reason to believe that this is a worldwide problem. A study in Australia surveyed 1372 women with GDM, of whom 27% reported having received an OGTT between 6 and 8 weeks postpartum.13 The self-reported nature of these data, however, means that overall testing rates may have been much lower, and this study was unable to determine the number of women having other tests of glucose tolerance in the postpartum period. In the USA, a study of 1127 women with confirmed GDM found that the proportion who completed a fasting glucose test within 3 months after delivery increased from 9.0% in 1999 to 50.3% in 2006.14 However, none of the women in this study received a postpartum OGTT. Lawrence et al.15 followed over 11 000 women from a managed care organisation in California between 1999 and 2006, and reported that about half of women received some testing up to 6 months postpartum, but only 21% had an OGTT. A recent study by Blatt et al.16 examined 23 000 women with GDM who could be followed postpartum, and found that 19% had diabetes testing within 6 months; the proportion who had an OGTT was not reported. These previous results are similar to our own; however, ours is by far the largest such study to date, covering an entire population of women and with complete follow up. Several small studies found much higher postpartum OGTT rates, between 40 and 50%, but these studies each reported findings from single academic centres so are not generalisable to the population.19–22

The barriers to postpartum diabetes testing are likely to be multifactorial, and several possible factors have been postulated, including lack of time for a new mother to undergo diabetes testing, lack of knowledge of testing recommendations, lack of awareness by the primary-care physician that a woman even had GDM during her pregnancy, failure of women to perceive themselves at high risk for diabetes, and fear of receiving bad news.23,24 Although it was not a goal of this study to examine these factors, we can conclude that another postulated barrier, disengagement by new mothers from the healthcare system, does not play a role. Indeed, >94% of them had postpartum ambulatory care with family physicians or obstetricians. This observation corroborates the findings of Smirnakis et al.25 who showed that women with GDM continue to engage in some aspects of preventative care postpartum: although only about 35% of women in their cohort underwent postpartum diabetes testing within 6 months, 94% had a Papanicolaou test.

The findings of this study could influence how knowledge translation interventions and policies to improve diabetes testing are delivered. For example, a randomised trial showed that postal reminders sent approximately 3 months after delivery to either the woman or her physician increased postpartum OGTT testing from 14% in the control group to over 50% in the intervention groups.26 Our study showed that almost all women had postpartum visits with either family physicians or obstetricians, so reminder systems ought to target these specialties to improve testing for this population. Alternatively, although relatively few women saw endocrinologists or internists postpartum, they ordered the majority of the postpartum OGTTs. This may have occurred because of referral bias, wherein women at higher risk for diabetes were selected to have ongoing follow up with these specialists. However, it may also have resulted from greater awareness among physicians in these specialties of type 2 diabetes risk and testing recommendations. Hence, formalised processes or policies to recall women who had GDM to these specialty clinics might also improve postpartum diabetes testing. Finally, the logistical difficulties of performing an OGTT for women with young infants suggest that the use of other tests might improve testing rates. In 2009, an international expert committee recommended the use of an HbA1c ≥6.5% for the diagnosis of type 2 diabetes with a single other test of glucose for confirmation.27 However, the sensitivity of these alternative diagnostic tests in this population remains to be established. A simpler diagnostic test combined with a formalised recall strategy might not only improve early detection of diabetes or pre-diabetes but also increase awareness among women of the future risk of developing type 2 diabetes after having GDM.

Our study has a number of strengths compared with previous studies of postpartum diabetes testing rates. First, it included a large, population-based sample over 14 years, and so was not influenced by specific local practice patterns or policies that can influence testing rates observed at a single centre or for a short time. Second, it included a comparison population without GDM, to account for secular changes in diabetes testing that went on in the general population, which previous studies did not. Third, it also showed that virtually all women in our cohort had visits with family physicians or obstetricians in the postpartum period. This information, combined with the data on who actually ordered diabetes testing in our cohort, will help to appropriately target interventions to improve postpartum testing rates in future studies. A key limitation is that our data source captured all laboratory service claims from community laboratories, but we were not able to capture laboratory tests carried out within the global budget of hospital inpatient and outpatient services. This limitation is unlikely to bias the trend in testing over time or the proportion of OGTTs versus less sensitive tests, but it may result in an underestimate of the true rate of postpartum testing in the population. However, a chart audit in one Ontario city found that more than 80% of postpartum OGTTs were performed in community laboratories submitting service claims,22 so it is unlikely that the rates of postpartum testing we found are dramatically underestimated. Furthermore, tests ordered by hospital-based obstetricians and endocrinologists would be more likely to be underestimated (although notably endocrinologists ordered the majority of tests that we found), but tests ordered by family physicians, who are mostly community-based, are probably not underestimated. Finally, there are systemic factors in the organisation of laboratory services in Ontario that would minimise the number of OGTTs performed in hospital laboratories: all laboratories operate on a walk-in basis only, so providers could not ‘schedule’ an OGTT for women at a specific laboratory; there is an order of magnitude more community laboratory sites than hospital laboratory sites in Ontario; and a common requisition form is used for all laboratories in the province, so women know that they can have their tests performed at any laboratory that is convenient for them.

In conclusion, diagnosing type 2 diabetes in women after GDM is important to reduce the risk of poor glycaemic control at the conception of a subsequent pregnancy, thereby reducing the risk of fetal malformations and other birth complications. Early detection of type 2 diabetes also allows for treatment to reduce the long-term impact of diabetes on the woman’s health. Testing with an OGTT may also detect women with pre-diabetes, for whom lifestyle and medication interventions can reduce the risk of progression to diabetes.9–11 Very few women with GDM, who are at markedly increased short-term risk of developing type 2 diabetes, actually received the recommended sensitive diabetes test within 6 months postpartum, and these rates were very slow to increase over the 14 years of observation. As virtually all women with GDM have postpartum ambulatory physician visits, the absence of testing represents a missed opportunity to diagnose diabetes. Interventions to improve testing rates in this high-risk population are essential.

Contribution to authorship

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure of interests
  8. Contribution to authorship
  9. Details of ethics approval
  10. Funding
  11. Acknowledgements
  12. References

BRS contributed to the conception of the study, to the acquisition, analysis and interpretation of data, and to drafting the article. JML contributed to the conception of the study, to the interpretation of data, and to critically revising the article. LLL and DSF contributed to the interpretation of data, and to critically revising the article.

Details of ethics approval

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure of interests
  8. Contribution to authorship
  9. Details of ethics approval
  10. Funding
  11. Acknowledgements
  12. References

The study was approved by the institutional review board of Sunnybrook Health Sciences Centre on 22 April 2009.

Funding

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure of interests
  8. Contribution to authorship
  9. Details of ethics approval
  10. Funding
  11. Acknowledgements
  12. References

BRS and LLL are funded by the Canadian Diabetes Association. BRS is also funded by the Canadian Institutes of Health Research. The Institute for Clinical Evaluative Sciences is funded in part by the Ontario Ministry of Health and Long-Term Care.

Acknowledgements

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure of interests
  8. Contribution to authorship
  9. Details of ethics approval
  10. Funding
  11. Acknowledgements
  12. References

The study was presented as an abstract at the 20th World Diabetes Congress in Montreal, Canada.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure of interests
  8. Contribution to authorship
  9. Details of ethics approval
  10. Funding
  11. Acknowledgements
  12. References
  • 1
    Feig DS, Zinman B, Wang X, Hux JE. Risk of development of diabetes mellitus after diagnosis of gestational diabetes. CMAJ 2008;179:22934.
  • 2
    King H. Epidemiology of glucose intolerance and gestational diabetes in women of childbearing age. Diabetes Care 1998;21 (Suppl 2):B913.
  • 3
    Bellamy L, Casas JP, Hingorani AD, Williams D. Type 2 diabetes mellitus after gestational diabetes: a systematic review and meta-analysis. Lancet 2009;373:17739.
  • 4
    Meltzer S, Leiter L, Daneman D, Gerstein HC, Lau D, Ludwig S, et al. 1998 clinical practice guidelines for the management of diabetes in Canada. CMAJ 1998;159 (Suppl 8):S129.
  • 5
    Canadian Diabetes Association Clinical Practice Guidelines Expert Committee. Canadian Diabetes Association 2003 clinical practice guidelines for the prevention and management of diabetes in Canada. Can J Diabetes 2003;27 (Suppl 2):S1115.
  • 6
    Canadian Diabetes Association Clinical Practice Guidelines Expert Committee. Canadian Diabetes Association 2008 clinical practice guidelines for the prevention and management of diabetes in Canada. Can J Diabetes 2008;32 (Suppl 1):S1201.
  • 7
    American Diabetes Association. Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Diabetes Care 1997;20:18397.
  • 8
    Reinblatt SL, Morin L, Meltzer SJ. The importance of a postpartum 75 g oral glucose tolerance test in women with gestational diabetes. J Obstet Gynaecol Can 2006;28:6904.
  • 9
    Pan XR, Li GW, Hu YH, Wang JX, Yang WY, An ZX, et al. Effects of diet and exercise in preventing NIDDM in people with impaired glucose tolerance. The Da Qing IGT and diabetes study. Diabetes Care 1997;20:53744.
  • 10
    Diabetes Prevention Program Research Group. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med 2002;346:393403.
  • 11
    Buchanan TA, Xiang AH, Peters RK, Kjos SL, Marroquin A, Goico J, et al. Preservation of pancreatic β-cell function and prevention of type 2 diabetes by pharmacological treatment of insulin resistance in high-risk Hispanic women. Diabetes 2002;51:2796803.
  • 12
    Clark HD, van Walraven C, Code C, Karovitch A, Keely E. Did publication of a clinical practice guideline recommendation to screen for type 2 diabetes in women with gestational diabetes change practice? Diabetes Care 2003;26:2658.
  • 13
    Morrison MK, Collins CE, Lowe JM. Postnatal testing for diabetes in Australian women following gestational diabetes mellitus. Aust NZ J Obstet Gynaecol 2009;49:4948.
  • 14
    Dietz PM, Vesco KK, Callaghan WM, Bachman DJ, Bruce FC, Berg CJ, et al. Postpartum screening for diabetes after a gestational diabetes mellitus-affected pregnancy. Obstet Gynecol 2008;112:86874.
  • 15
    Lawrence JM, Black MH, Hsu JW, Chen W, Sacks DA. Prevalence and timing of postpartum glucose testing and sustained glucose dysregulation after gestational diabetes mellitus. Diabetes Care 2010;33:56976.
  • 16
    Blatt AJ, Nakamoto JM, Kaufman HW. Gaps in diabetes screening during pregnancy and postpartum. Obstet Gynecol 2011;117:618.
  • 17
    Hux JE, Ivis F, Flintoft V, Bica A. Diabetes in Ontario: determination of prevalence and incidence using a validated administrative data algorithm. Diabetes Care 2002;25:5126.
  • 18
    Retnakaran R, Qi Y, Sermer M, Connelly PW, Hanley AJG, Zinman B. Glucose intolerance in pregnancy and future risk of pre-diabetes or diabetes. Diabetes Care 2008;31:202631.
  • 19
    Russell MA, Phipps MG, Olson CL, Welch HG, Carpenter MW. Rates of postpartum glucose testing after gestational diabetes mellitus. Obstet Gynecol 2006;108:145662.
  • 20
    Hunt KJ, Conway DL. Who returns for postpartum glucose screening following gestational diabetes mellitus? Am J Obstet Gynecol 2008;198:404.e1e6.
  • 21
    Kwong S, Mitchell RS, Senior PA, Chik CL. Postpartum diabetes screening: adherence rate and the performance of fasting plasma glucose versus oral glucose tolerance test. Diabetes Care 2009;32:22424.
  • 22
    Shea AK, Shah BR, Clark HD, Malcolm J, Walker M, Karovitch A, et al. The effectiveness of implementing a reminder system into routine clinical practice: does it increase postpartum screening in women with gestational diabetes? Chronic Dis Can 2011;31:5864.
  • 23
    Bennett WL, Ennen CS, Carrese JA, Hill-Briggs F, Levine DM, Nicholson WK, et al. Barriers to and facilitators of postpartum follow-up care in women with recent gestational diabetes mellitus: a qualitative study. J Womens Health (Larchmt) 2011;20:23945.
  • 24
    England LJ, Dietz PM, Njoroge T, Callaghan WM, Bruce C, Buus RM, et al. Preventing type 2 diabetes: public health implications for women with a history of gestational diabetes mellitus. Am J Obstet Gynecol 2009;200:365.
  • 25
    Smirnakis KV, Chasan-Taber L, Wolf M, Markenson G, Ecker JL, Tadhani R. Postpartum diabetes screening in women with a history of gestational diabetes. Obstet Gynecol 2005;106:1297303.
  • 26
    Clark HD, Graham ID, Karovitch A, Keely EJ. Do postal reminders increase postpartum screening of diabetes mellitus in women with gestational diabetes mellitus? A randomized controlled trial. Am J Obstet Gynecol 2009;200:634.e1e7.
  • 27
    International Expert Committee. International Expert Committee report on the role of the A1C assay in the diagnosis of diabetes. Diabetes Care 2009;32:132734.