The prevalence of 6 weeks postpartum abnormal glucose tolerance in Caucasian women with gestational diabetes

diabetes research and clinical practice 84 (2009) 239–244

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The prevalence of 6 weeks postpartum abnormal glucose tolerance in Caucasian women with gestational diabetes Jarosław Ogonowski a,b, Tomasz Miazgowski a,b,* a b

Department of Hypertension and Internal Medicine, Pomeranian Medical University, Szczecin, Poland Outpatient Clinic for Diabetic Pregnant Women, Szczecin, Poland

article info

abstract

Article history:

Aims: To evaluate the incidence of impaired glucose tolerance (IGT), impaired fasting

Received 22 October 2008

glucose (IFG) and diabetes in 318 Caucasian women with gestational diabetes (GDM) at 6

Received in revised form

weeks postpartum.

30 March 2009

Methods: All women had 75 g OGTT and the following data were collected: age, height,

Accepted 2 April 2009

weight, results of the challenge 50 g and diagnostic 75 g OGTT, and glycated hemoglobin (HbA1c). Results: 13.5% of women had abnormal glucose tolerance, including 1.3% of diabetes, 2.5% of

Keywords:

IFG and 7.5% of IGT. None of the prepregnancy independent variables, such as age, body

Gestational diabetes

mass index, prior GDM, prior macrosomia, family history of type 2 diabetes and multiparity

Postpartum abnormal glucose

was a predictor for the abnormal OGTT. In contrast, pregnancy-related risk factors, like

tolerance

gestational week at GDM diagnosis (P = 0.001), glucose values in the challenge (P = 0.007) and diagnostic (P = 0.02) OGTTs and HbA1c (P = 0.01) were significantly associated with the persistence of glucose intolerance after delivery. Conclusion: The incidence of postpartum abnormal glucose tolerance in Caucasian women with GDM was 13.5% and was associated with an early diagnosis of GDM, severity of hyperglycemia and requirement for insulin therapy. The diagnosis of GDM should initiate a lifelong monitoring of glucose tolerance to minimize the risk of developing overt diabetes. # 2009 Elsevier Ireland Ltd. All rights reserved.

1.

Introduction

It has been well documented that prior gestational diabetes mellitus (GDM) substantially increases the risk for type 2 diabetes. A meta-analysis of 28 studies performed from 6 weeks to 28 years after delivery revealed that cumulative incidence of diabetes after GDM ranged from 2.6% up to 70%, depending on which populations were studied, which criteria were used for diagnosis of GDM, and how long was a period of time from delivery to the assessment [1]. Current guidelines published by the World Health Organization (WHO) [2],

American Diabetes Association (ADA) [3], and the Fifth International Workshop-Conference on GDM [4] recommend an early oral glucose tolerance test (OGTT) that should be performed within 6–12 weeks after delivery. The rationale for performing an early OGTT are as follows: (i) there is a relatively high prevalence of glucose abnormalities detected within first 3 months postpartum, reaching 17–23% of all cases with prior GDM; (ii) abnormal early OGTT results identify women at high risk of developing diabetes over the next 5–10 years; (iii) there is an ample clinical trial evidence in women with glucose intolerance that type 2 diabetes can be delayed or prevented by

* Corresponding author at: Department of Hypertension and Internal Diseases, Pomeranian Medical University, Unii Lubelskiej 1, 71-252 Szczecin, Poland. Tel.: +48 602398723; fax: +48 91 4542042. E-mail address: [email protected] (T. Miazgowski). 0168-8227/$ – see front matter # 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.diabres.2009.04.003

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diabetes research and clinical practice 84 (2009) 239–244

lifestyle interventions or modest and perhaps intermittent drug therapy; (iv) women with prior GDM, impaired glucose tolerance (IGT) or impaired fasting glucose (IFG) have increased risk for cardiovascular events, and interventions may also reduce subsequent cardiovascular disease, which is the leading cause of death in both types of diabetes; and (v) identification, treatment, and planning pregnancy in women developing diabetes after GDM should reduce subsequent early fetal loss and major congenital malformations [5]. However, studies evaluating the effectiveness of early OGTT in women with prior GDM yielded ambiguous results. The potential source of this inconsistency might be that different diagnostic criteria for GDM were applied and variety of populations with known different risk of developing diabetes was studied. Majority of studies that have been performed so far evaluated heterogeneous, mixed or non-white populations, in which GDM was diagnosed by OGTT using 100 g glucose load [6–14]. The incidence of early postpartum abnormal glucose tolerance in these studies ranged from 18.5% to 42.5%, including 4.5–16% of diabetes. On the other hand, in Caucasians, the relevant incidence rate ranged 7– 22.3% for all types of abnormal glucose tolerance, and 2.4–8.8% for diabetes [5,15–18], what reflects a relatively low risk (approximately 2-fold) for developing diabetes after GDM in this group of women in comparison with other ethnic groups. In some countries, predominantly in Europe, GDM as well as diabetes after GDM are diagnosed by the WHO diagnostic tests. However, only a few studies estimated the incidence of early postpartum glucose intolerance after GDM in Caucasian women using the same tests for diagnosis of GDM, IGT, IFG and diabetes [18,19]. Based on the foregoing, the aim of our study was to evaluate the incidence of abnormal glucose metabolism (IGT, IFG and diabetes) in the homogenous sample of Caucasian women 6 weeks after GDM and to assess, which of pregravid factors or factors related with pregnancy were associated with the persistence of abnormal glucose profile after delivery.

2.

Materials and methods

The study was performed on Caucasian women aged >18 years which were diagnosed as having glucose intolerance during pregnancy and were referred to the Outpatient Clinic for Diabetic Pregnant Women in Szczecin (northwest part of Poland) between January 2005 and December 2007. We analyzed data collected from 855 women with GDM. Women with pregravid diabetes or multiple pregnancies were not analyzed. GDM was diagnosed by a two-step diagnostic procedure using a 50 g glucose challenge test and a 75 g oral glucose tolerance test (OGTT). In Poland, as a routine procedure, at the initial obstetric visit fasting serum glucose is measured and data on risk factors for GDM, such as prior GDM, prior macrosomia, pregravid obesity, age, prior multiparity, and unfavorable obstetric outcomes in history are collected. Women with increased fasting glucose or with at least one risk factor for GDM are referred to early diagnostic tests; otherwise glucose tests are performed at 24–28 weeks’ gestation.

The challenge test entailed oral administration of 50 g glucose, regardless of the length of time since the last meal, with a measurement of plasma glucose 1 h later. Women with fasting glucose between 100 mg/dl (5.6 mmol/l) and 125 mg/dl (6.9 mmol/l), fasting glucose 126 mg/dl (7.0 mmol/l) but <100 mg/dl (5.6 mmol/l) in another measurement on a subsequent day, or with 2-h glucose level in the challenge test between 140 mg/dl (7.8 mmol/l) and 200 mg/dl (11.1 mmol/l) were referred for a 75 g OGTT. Women with 2-h glucose level >200 mg/dl (11.1 mmol/l) in the challenge test were classified as GDM. By the results of diagnostic OGTT, GDM was diagnosed if either the fasting glucose level was 126 mg/dl (7.0 mmol/l) or the 2-h glucose concentration was 140 mg/dl (7.8 mmol/l), according to the WHO criteria [2]. Routinely, all GDM women were educated and motivated by personnel adequately trained in patient education, and patient education skills were reviewed, evaluated and reinforced on a regular basis. GDM women were trained in achieving effective self-monitoring of blood glucose control by at least four measurements a day (fasting and 1 h after meal) or more according to need, as well as in self-adjustment of insulin dose in case of inadequate glycemic control. Treatment regimen included diet, insulin NPH given at bedtime and short acting human insulin before meals. Achievement of the therapeutic goals was defined as follows: fasting blood glucose of 60–90 mg/dl (3.3–5.0 mmol/l) and <130 mg/dl (7.3 mmol/l) 1 h after meals and was evaluated at each visit performed on a weekly basis. All women with GDM were recommended to have an early 75 g OGTT after delivery. At the visit performed 6 weeks after delivery, the following data were collected: age, height, weight before pregnancy, serum glucose at the first obstetric visit, results of the challenge 50 g and diagnostic 75 g OGTT, glycated hemoglobin (HbA1c) at the time of GDM diagnosis, time of the start of insulin therapy, and a dose of insulin at 37 weeks’ gestation. Serum glucose was assessed by enzymatic method (Cobas Integra 800; Roche Diagnostica GmBH, Mannheim, Germany); the intraassay coefficient of variation (CV) was 1.09% and interassay CV was 0.9%. HbA1c was measured using turbidimetric inhibition assay (Cobas Integra 800; Roche Diagnostica GmBH, Mannheim, Germany); intra- and interassay CVs were 2.3% and 2.2%, respectively. On the basis of 75 g OGTT performed at 6 weeks after delivery, diabetes was diagnosed if either the fasting glucose level was 126 mg/dl (7.0 mmol/l) or the 2-h glucose concentration was 200 mg/dl (11.1 mmol/l), according to the WHO criteria [2]. IGT was diagnosed if 2-h glucose was between 140 mg/dl and 199 mg/dl (7.8–11.0 mmol/l) and IFG was diagnosed if fasting glucose was between 100 mg/dl and 125 mg/dl (5.5–6.9 mmol/l) [19]. Body mass index (BMI) was calculated from weight (kilograms) and height (meters) measured with a single fixed stadiometer at the initial visit. The protocol of study was approved by the institutional review board.

2.1.

Statistical analysis

The distribution of continuous variables was tested for normality by the Shapiro–Wilk test. The chi-square test and unpaired t-tests were used to compare baseline characteristics

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diabetes research and clinical practice 84 (2009) 239–244

Table 1 – Characteristics of women who returned and failed to return for postpartum OGTT.

Age (years) Weight before pregnancy (kg) Height (cm) Prepregnancy body mass index (kg/m2) Gestational week at GDM diagnosis Fasting glucose level at first obstetric visit (mg/dl) Glucose level in challenge 50-g OGTT (mg/dl) Glycated hemoglobin at GDM diagnosis (%) Glucose level at 0 min OGTT (mg/dl) Glucose level at 120 min OGTT (mg/dl) Insulin treated (%) Insulin dose at 37 weeks’ gestation (units)

Women not returning for postpartum OGTT (N = 537)

P

Women returning for postpartum OGTT (N = 318)

29.89  0.22 66.5  0.65 164.3  0.26 24.57  0.22 28.0  0.21 86.47  0.72 164.45  1.14 5.33  0.02 88.08  0.64 161.17  1.07 31.1 20.28  1.24

0.002 0.465 0.626 0.478 0.196 0.692 0.264 0.929 0.092 0.155 0.0003 0.832

30.96  0.27 65.65  0.79 164,5  0.33 24.37  0.29 27.55  0.27 85.61  0.71 167.58  1.75 5.33  0.03 85.98  0.66 162.20  1.08 43.3 19.68  1.26

Data are expressed as mean  SE.

between women with GDM who returned and failed to return for 75 g OGTT at 6 weeks postpartum, and between woman with normal and postpartum abnormal glucose tolerance. Univariate and multiple logistic regression models were used to test for relationships between the probability of occurrence of abnormal OGTT at 6 weeks after delivery and prepregnancy (age, height, prepregnancy BMI, prior GDM, prior macrosomia, history of type 2 diabetes in the first degree relatives, and multiparity) or pregnancy-related risk factors (week of GDM diagnosis, fasting glucose concentration at the first obstetric visit, glucose values in the challenge and diagnostic OGTT, and HbA1c); the results of the analysis were expressed as odds ratios (OR) and 95% confidence intervals (CI). The level of significance was set at P < 0.05.

3.

Results

Of the total of 855 women with GDM, 318 women (37%) referred to 75 g OGTT between 5 and 9 weeks after delivery (mean 6.0  0.2 weeks). Clinical characteristics of women who returned and did not return for OGTT are summarized in

Table 1. In general, women who had OGTT were significantly older and frequently required insulin therapy but had similar parameters of blood glucose control, as compared to women in whom OGTT was not performed. On the basis of OGTT results in 43 women (13.5%) abnormal glucose metabolism (IGT, IFG and diabetes) was diagnosed. As given in Table 2, in comparison with women who had normal OGTT, women with glucose intolerance had similar anthropometric measurements but during pregnancy they required frequently insulin therapy given in higher doses. The frequency distribution of prediabetes and diabetes in the studied sample is given in Table 3. Diabetes was diagnosed in 1.3% of women, IFG in 2.5% and IGT in 7.5%. Seven women (2.2%) met criteria for both IFG and IGT. Women with GDM treated insulin had more frequently abnormal OGTT results, as compared to women treated with diet only (19.7% vs. 8.8%; P < 0.001). In all women who had 75 g OGTT 6 weeks after delivery, univariate logistic regression models were used to test for relationships between the probability of occurrence of abnormal OGTT 6 weeks after delivery and prepregnancy or pregnancy-related risk factors for GDM. The analysis revealed that none of the prepregnancy independent variables, such as

Table 2 – Comparison of GDM women with normal and abnormal glucose tolerance.

Age (years) Weight before pregnancy (kg) Height (cm) Prepregnancy body mass index (kg/m2) Fasting glucose at the first obstetric visit (mg/dl) Glucose level at challenge OGTT (mg/dl) Glycated hemoglobin at GDM diagnosis (%) OGTT 0 min during pregnancy (mg/dl) OGTT 120 min during pregnancy (mg/dl) Insulin treated (%) Insulin dose at 37 weeks’ gestation (units) Follow-up after delivery (weeks) OGTT 0 min at follow-up (mg/dl) OGTT 60 min at follow-up (mg/dl) OGTT 120 min at follow-up (mg/dl) Data are expressed as mean  SE.

Normal glucose tolerance (N = 275)

P

30.77  0.29 65.3  0.83 164.37  0.37 24.28  0.31 84.55  0.68 165.8  1.78 5.29  0.03 85.0  0.68 161.02  1.05 40.0 17.29  1.13 6.31  0.04 81.8  0.44 119.97  1.65 92.9  1.22

0.179 0.485 0.262 0.754 0.028 0.002 0.046 0.003 0.005 0.005 0.0001 0.451 0.0001 0.0001 0.0001

Abnormal glucose tolerance (N = 43) 31.93  0.74 68.33  2.68 165.1  1.06 25.16  0.99 91.49  2.76 183.6  6.48 5.52  0.10 91.98  2.12 171.32  4.03 62.8 30.11  4.03 6.21  0.07 94.4  2.4 166.1  5.61 147.9  4.46

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Table 3 – Frequency distribution of postpartum normal and abnormal glucose tolerance in women with gestational diabetes treated with diet or diet and insulin.

Overall GDM GDM treated with diet GDM treated with insulin

Normal glucose tolerance

Impaired fasting glucose (IFG)

Impaired glucose tolerance (IGT)

IFG/IGT combined

Diabetes

275 (86.5%) 165 (91.1%) 110 (80.3%)

8 (2.5%) 5 (2.8%) 3 (2.2%)

24 (7.5%) 9 (5.0%) 15 (10.9%)

7 (2.2%) 1 (0.5%) 3 (2.2%)

4 (1.3%) 1 (0.5%) 3 (2.2%)

Total 318 (100%) 181 (56.9%) 137 (43.1%)

Table 4 – Associations between postpartum abnormal glucose tolerance and pregnancy-related risk factors.

Gestational week at GDM diagnosis HbA1c (%) Fasting glucose at the first obstetric visit (mg/dl) Glucose level at challenge OGTT (mg/dl) OGTT 0 min (mg/dl) OGTT 120 min (mg/dl) Insulin dose at 37 weeks’ gestation (units) Gestational week at start of insulin therapy

Overall GDM

GDM diet treated

0.91 (0.86–0.96) P = 0.001 2.36 (1.19–4.68) P = 0.01 1.05 (1.02–1.08) P = 0.001 1.025 (1.01–1.08) P = 0.007 1.05 (1.02–1.08) P = 0.0009 1.026 (1.01–1.04) P = 0.002 1.053 (1.02–1.08) P = 0.0009 0.82 (0.74–0.91) P = 0.0004

0.97 (0.88–1.08) P = 0.62 1.51 (0.41–5.59) P = 0.53 1.01 (0.96–1.07) P = 0.56 1.016 (0.99–1.05) P = 0.27 1.058 (1.01–1.11) P = 0.02 1.03 (1.00–1.06) P = 0.03

GDM insulin treated 0.88 (0.81–0.96) P = 0.004 2.47 (1.02–5.95) P = 0.04 1.068 (1.02–1.11) P = 0.002 1.028 (1.00–1.05) P = 0.03 1.036 (0.99–1.07) P = 0.049 1.02 (1.0–1.04) P = 0.04

Data are Odds ratio (95%CI).

age (OR 1.53, 95%CI 0.98–1.13), prepregnancy BMI (OR 1.03, 95%CI 0.97–1.09), prior GDM (OR 1.66, 95%CI 0.53–5.24), prior macrosomia (OR 1.86, 95%CI 0.71–4.92), history of type 2 diabetes in the first degree relatives (OR 1.84,95%CI 0.12–4.16), and multiparity (OR 1.18, 95%CI 0.93–1.49) was a predictor for the abnormal OGTT result. In contrast, pregnancy-related risk factors, like gestational week at GDM diagnosis, fasting glucose concentration at the first obstetric visit, glucose values both in the challenge and diagnostic OGTT as well as HbA1c were significantly associated with the persistence of glucose intolerance after delivery in pregnancies complicated by GDM (Table 4). Severity of GDM was determined by requirement of insulin therapy, early start of insulin therapy during pregnancy and total dosage of insulin at the termination. Requirement of insulin therapy of GDM was a strong predictor of glucose intolerance after delivery (OR 2.53, 95%CI 1.3–4.93; P = 0.006) and this relationship was significant in a dose-dependent manner—an increase of insulin dose by unit was associated with a 5% risk increase for glucose intolerance after pregnancy. By multiple logistic regression, prepregnancy risk factors did not influenced the risk of postpartum glucose intolerance, whereas pregnancy-related risk indicators: fasting glucose at the first obstetric visit (OR 1.05, 95%CI 1.01–1.08; P = 0.002), requirement of insulin therapy (OR 2.16, 95%CI 1.01– 4.63; P = 0.046) and 2-h glucose concentration in the 75 g OGTT (OR 1.02, 95%CI 1.0–1.04; P = 0.003) substantially increased the risk. However, by adding other pregnancy-related risk factors to this model, these associations were not significant.

4.

Discussion

In the present study we found that in Caucasian women with GDM glucose intolerance defined as IGT, IFG and diabetes persisted in 13.5% of population 6 weeks after delivery. Majority of this glucose intolerance were IGT and IFG, and as low as 1.3% of women were classified as diabetes, according

to the WHO diagnostic criteria [2]. These findings are in contrast with previous studies reporting higher prevalence of glucose intolerance diagnosed early postpartum, ranging 7– 42%, including 2.4–16% of diabetes [5–18]. These discrepancies may be explained, at least partially, by the fact that some of these studies were performed on the ethically mixed or highrisk populations. It is also interesting to note that in our sample women with GDM had relatively low pregravid body mass index in comparison with other studies. Moreover, in cited studies different diagnostic criteria for GDM were applied. Only a few studies assessed the frequency of postpartum abnormal glucose tolerance in Caucasian women with GDM, in which glucose intolerance and GDM were diagnosed by the same, most recent WHO criteria. Two studies reported a relatively low prevalence of 7% and 8% [17,18]. However, in both studies diagnostic OGTT was preceded by selective screening based on traditional risk factors, and therefore women with relatively higher risk for developing GDM were identified. On the contrary, our cohort was screened by universal approach what probably may reflect a real prevalence of GDM in Caucasian women [20]. Moreover, in our analyses we used lower threshold for diagnosis of IFG, according to current recommendations [19]. An accumulating body of evidence indicates that an early postpartum screening performed in GDM women first of all identifies cases with abnormal glucose tolerance, already existing before pregnancy [7,9,10,15,16,21]. Our results are in line with this thesis and we found that in group of women with abnormal glucose tolerance diagnosed 6 weeks after delivery, GDM was detected in early pregnancy and that the gestational age at diagnosis was a strong predictor for developing of prediabetes or diabetes. Moreover, in women with postpartum abnormal glucose tolerance HbA1c level at GDM diagnosis was increased, reflecting not only more severe course of the disease, but also, as a retrospective parameter, may indicate that the exposure on hyperglycemia lasted for longer period of time. This is consistent with recent report demonstrating

diabetes research and clinical practice 84 (2009) 239–244

increased HbA1c levels at the third trimester of pregnancy complicated by GDM in women developing glucose intolerance early after delivery [21]. Majority of GDM women in the present study had normal postpartum glucose tolerance. Therefore, using logistic regression we analyzed some prepregnancy and pregnancyrelated potentially confounding variables that might be helpful in the identification of patients at risk for abnormal glucose tolerance after delivery. In contrast to some earlier reports [8–10,22], but in line with the others [6,7,15,17], we could not demonstrate any predictive value of prepregnancy risk factors, such as BMI, age, family history of diabetes, prior GDM, prior macrosomia, or multiparity. These discrepancies indicate that, aside from genetic predisposition, the impact of risk indicators on postpartum glucose tolerance may be influenced by ethnic composition of the studied populations. This is consistent with our previous report demonstrating a low predictive value of traditional risk factors in identifying women at risk for GDM in the large, homogenous sample of Caucasian women [20]. On the other hand, factors indicating more severe course of GDM were significantly associated with high risk of prediabetes and diabetes 6 weeks postpartum, particularly in insulin-treated women. Among these factors the strongest single predictor was insulin therapy per se—GDM women that required insulin during pregnancy had 2.5-fold increased risk of abnormal glucose tolerance after delivery. This finding supports some earlier, similar observations [7–9,15]. Despite the fact that WHO and ADA in all GDM women strongly recommend OGTT at 6–12 weeks postpartum, usually less than 50% of women returned for glucose testing. In our study only 37% of women returned for OGTT, similarly like in other studies [11,13,14]. It has been shown that the American obstetrician-gynecologists in a daily routine clinical practice recommended early OGTT for only 33% of women with GDM [22]. This is in contrast with a declaration the American College of Obstetricians and Gynecologists (ACOG) fellows that as much as 74% of GDM women returned for glucose testing after delivery [23]. The main weakness of the present study is that GDM women treated with insulin were overrepresented in our sample what might overestimate the prevalence of postpartum glucose intolerance. This may indicate that women who returned for postpartum glucose testing had more severe GDM, and therefore it seems likely that they displayed healthier lifestyle behaviour attitudes and were better motivated than women who failed to return. Previous studies also emphasized such relationships [7]. In general, Caucasian women are at low risk of glucose intolerance in comparison with some other ethnic groups. Moreover, we showed that women with GDM treated with diet only had a 2-fold lower prevalence of abnormal glucose tolerance postpartum than women with GDM requiring insulin therapy. This may rise a question whether to apply an early postpartum OGTT for all Caucasian GDM women or rather to restrict this testing only to women with GDM treated with insulin. Some studies have suggested that postpartum glucose screening is not warranted for women at low risk who do not require insulin during pregnancy [8] and is less cost effective in Caucasians [17]. An answer for this dilemma

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has been suggested in other studies evaluating glucose tolerance after GDM in longer follow-ups. In Caucasian women a follow-up at 3–12 months showed significant increase of the abnormal glucose tolerance rate after GDM up to 14–31%, including 2–9% of diabetes [21,24,25]. In a 3-year follow-up the cumulative incidence of IGT and diabetes in Polish women reached 41.5% [26]. In longer follow-ups (3–15 years after GDM) the rate of glucose tolerance was some higher ranging 28–53% for prediabetes, and 11–43% for diabetes [27–30]. Lauenborg et al. [31] found that even in women with GDM treated with diet only the prevalence of the metabolic syndrome is 3-fold higher than in the general population in a 10-year follow-up. Interestingly, European women with a history of GDM and postpartum normoglycemia had insulin resistance and impaired beta-cell function [32,33], and therefore are at risk for cardiovascular diseases [34]. These findings suggest that after GDM the risk of glucose intolerance persists, requiring lifelong evaluation to completely capture the risk of diabetes. When cumulative incidence of diabetes is plotted against follow-up after delivery, rapid conversion to diabetes is usually seen over the first 5 years, with a slower progression subsequently [35]. These observations, along with the results of present study confirm the rationale for early postpartum OGTT in all women with a history of GDM, regardless of the ethnicity, as well as for the necessity of lifelong monitoring of glucose tolerance in these cases. Which tests should be used for the regular, lifelong testing is less clear since current guidelines recommend both OGTT and fasting glucose level [4]. OGTT, albeit less cost effective, seems to be more adequate than the fasting glucose testing [36]. Earlier studies have demonstrated the limitations of the fasting glucose as a screen, with only 34% of IGT or diabetes being picked up by those women with impaired fasting glucose levels [35]. In conclusion, the incidence of postpartum abnormal glucose tolerance at 6-week follow-up in Caucasian women with GDM was 13.5% and was associated with an early diagnosis of GDM during pregnancy, severity of hyperglycemia and requirement for insulin therapy. The diagnosis of GDM should initiate a lifelong monitoring of glucose tolerance to minimize the risk of developing overt diabetes.

Conflict of interest There are no conflicts of interest.

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