Early screening for gestational diabetes mellitus: a meta-analysis of randomized controlled trials

The Relationship between a High Carbohydrate Diet and Oral Glucose Tolerance Test in Pregnancy

OBJECTIVE

The aim of this study is to examine the impact of carbohydrate ratios in the diet consumed one day prior to the 75-g oral glucose screening test on both the screening test values and the diagnosis of gestational diabetes mellitus in the unselective pregnant population.

MATERIAL-METHOD

83 pregnant women who were under observation in the antenatal clinic of our hospital and underwent glucose tolerance tests were included in the study. The patients were given training by a dietitian to keep nutrition records of the day prior to glucose loading during their previous visits before any glucose loading. A carbohydrate intake of 40-60% was considered as the normal range in terms of the percentage of carbohydrates in the diet. A carbohydrate percentage above 60% was considered to be a high carbohydrate intake. The carbohydrate percentages in their diet over the past 24 hours was compared with the effect on the glucose tolerance test.

RESULTS

Out of the 83 pregnant women included in the study, 40 of them had a high carbohydrate diet (HCD) prior to the oral glucose tolerance test (OGTT), and the average carbohydrate percentage of this diet was found to be 62%. The remaining 43 patients had an average carbohydrate percentage of 49% and belonged to the group that had a normal carbohydrate diet (NCD). Out of the 83 pregnant women, 33 of them were at high risk for gestational diabetes mellitus (GDM). In the high-risk patient group, 16 patients had an NCD intake, while 17 patients had a HCD intake. It was determined that a high carbohydrate diet had no significant effect on fasting, first-hour, and second-hour glucose levels, as well as the diagnosis of gestational diabetes mellitus (GDM), in both the unselective population and the high-risk patient population.

CONCLUSION

In our study, we concluded that the high carbohydrate ratios in the diets of pregnant women one day prior did not affect the OGTT results or the GDM ratios. This indicates that there is no need for a preparatory diet prior to the OGTT in women with normal dietary habits.

Routine screening for gestational diabetes: a review

PURPOSE OF REVIEW

Rates of gestational diabetes mellitus (GDM) throughout the world continue to increase associated with the increasing rates of obesity. Given this epidemiologic burden, the importance of proper screening, diagnosis, and management cannot be understated. This review focuses on the current screening guidelines utilized throughout the world and new data recently published regarding the most optimal screening techniques and future directions for research.

RECENT FINDINGS

Despite unanimous opinion that GDM warrants screening, the optimal screening regimen remains controversial. Notably, in the United States per the consensus recommendation by the American College of Obstetrics and Gynecology and the Society for Maternal-Fetal Medicine, a 2-step screening approach is often used. Recently, there have been multiple studies published that have compared the 1-step and 2-step screening process with respect to GDM incidence and perinatal outcomes. These new findings are summarized below.

SUMMARY

Utilization of the 1-step screening as opposed to the 2-step screening results in an increased diagnosis of GDM without significant population level benefit in outcomes. However, these studies remain underpowered to allow for meaningful comparison of outcomes in those diagnosed with GDM.

Sensitivity, specificity, and diagnostic accuracy of WHO 2013 criteria for diagnosis of gestational diabetes mellitus in low risk early pregnancies: international, prospective, multicentre cohort study

Objective

To evaluate the predictability of gestational diabetes mellitus wth a 75 g oral glucose tolerance test (OGTT) in early pregnancy, based on the 2013 criteria of the World Health Organization, and to test newly proposed cut-off values.

Design

International, prospective, multicentre cohort study.

Setting

Six university or cantonal departments in Austria, Germany, and Switzerland, from 1 May 2016 to 31 January 2019.

Participants

Low risk cohort of 829 participants aged 18-45 years with singleton pregnancies attending first trimester screening and consenting to have an early 75 g OGTT at 12-15 weeks of gestation. Participants and healthcare providers were blinded to the results.

Main outcome measures

Fasting, one hour, and two hour plasma glucose concentrations after an early 75 g OGTT (12-15 weeks of gestation) and a late 75 g OGTT (24-28 weeks of gestation).

Results

Of 636 participants, 74 (12%) developed gestational diabetes mellitus, according to World Health Organization 2013 criteria, at 24-28 weeks of gestation. Applying WHO 2013 criteria to the early OGTT with at least one abnormal value gave a low sensitivity of 0.35 (95% confidence interval 0.24 to 0.47), high specificity of 0.96 (0.95 to 0.98), positive predictive value of 0.57 (0.41 to 0.71), negative predictive value of 0.92 (0.89 to 0.94), positive likelihood ratio of 10.46 (6.21 to 17.63), negative likelihood ratio of 0.65 (0.55 to 0.78), and diagnostic odds ratio of 15.98 (8.38 to 30.47). Lowering the postload glucose values (75 g OGTT cut-off values of 5.1, 8.9, and 7.8 mmol/L) improved the detection rate (53%, 95% confidence interval 41% to 64%) and negative predictive value (0.94, 0.91 to 0.95), but decreased the specificity (0.91, 0.88 to 0.93) and positive predictive value (0.42, 0.32 to 0.53) at a false positive rate of 9% (positive likelihood ratio 5.59, 4.0 to 7.81; negative likelihood ratio 0.64, 0.52 to 0.77; and diagnostic odds ratio 10.07, 6.26 to 18.31).

Conclusions

The results of this prospective low risk cohort study indicated that the 75 g OGTT as a screening tool in early pregnancy is not sensitive enough when applying WHO 2013 criteria. Postload glucose values were higher in early pregnancy complicated by diabetes in pregnancy. Lowering the postload cut-off values identified a high risk group for later development of gestational diabetes mellitus or those who might benefit from earlier treatment. Results from randomised controlled trials showing a beneficial effect of early intervention are unclear.

Trial registration

ClinicalTrials.gov NCT02035059.

Combining HbA1c and insulin resistance to assess the risk of gestational diabetes mellitus: a prospective cohort study

OBJECTIVE

To investigate the association of glycated hemoglobin (HbA1c) and homeostasis model assessment insulin resistance (HOMA-IR) with gestational diabetes mellitus (GDM) risk.

METHODS

Data for this study were from a prospective cohort in Hangzhou, China. We included pregnant women with HbA1c, fasting insulin, and fasting glucose (FG) measured at 15-20 weeks of gestation and underwent oral glucose tolerance test (OGTT) at 24-28 weeks. Based on HbA1c and HOMA-IR, participants were divided into four groups. We estimated the odds ratios (OR) with 95% confidence intervals (CI) to assess the associations of HbA1c and HOMA-IR with GDM occurrence. Finally, we the potential additive interaction between HbA1c and HOMA-IR by calculating relative excess risk due to interaction (RERI) and the attributable proportion due to interaction (AP).

RESULT

462 pregnant women were included, of whom 136 (29.44%) developed GDM. Based on HbA1c and HOMA-IR, the study population was divided into four groups, with the percentages of each group being 51.30%, 15.58%, 20.56%, and 12.55%, respectively. The incidence of GDM increased with the increase of HOMA-IR and HbA1c, respectively, and the risk of GDM was significantly increased when both HOMA-IR and HbA1c were elevated. However, no such risk was observed in pregnant women < 35 years. Finally, we found significantly higher FG at 24-28 weeks in the high HOMA-IR and HbA1c group among GDM-positive pregnant women.

CONCLUSIONS

The incidence of GDM increased with increasing HbA1c and HOMA-IR, and the risk of GDM was significantly increased when both HbA1c and HOMA-IR were elevated. This finding may help to identify high-risk women for GDM early in pregnancy and provide timely interventions.