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Gestational Diabetes Mellitus: Revised Diagnostic Criteria Can Help Improve Pregnancy Outcomes

Feb 3, 2018
 

A closer look into what’s new according to the WHO shows if more women are at risk for gestational diabetes than thought.

Active screening for gestational diabetes mellitus (GDM) is recommended to reduce the risk of pregnancy-related complications. These complications include gestational hypertension, caesarean sections, and an array of neonate issues. The guidelines used for diagnosing and managing GDM vary from group to group. In hopes of better identifying patients at risk, the WHO has come to adopt a more stringent philosophy based on the International Association of the Diabetes and Pregnancy Study Groups (IADPSG) consensus panel recommended criteria. The new WHO 2013 criteria uses more aggressive fasting plasma glucose and 2-hour plasma glucose (2HG) readings. These guidelines are yet to be accepted and supportive evidence is limited at this time.  Some concerns include cost increase, unclear optimal glucose targets for GDM, and the lack of cost-effectiveness analyses. The purpose of this study is to evaluate the outcomes of adopting WHO 2013 criteria vs. the older WHO 1999 criteria.

A retrospective study was conducted to analyze data of oral glucose tolerance tests (OGTT) collected from 10,642 Dutch women at risk for GDM. The women were between 24 and 28 weeks pregnant. If they had one or more risk factors for GDM, they were recommended for the 75g OGTT test. The risk factors include: pre-pregnancy obesity, history of GDM, first degree familial history of diabetes, history of macrosomic babies, intrauterine fetal death, polycystic ovarian syndrome, and being of an ethnic background. Based on the WHO 1999 criteria, women were treated for GDM if their fasting plasma glucose was ³7.0mmol/l and/or 2HG ³7.8mmol/l.  Treatment consisted of dietary counseling by a dietitian who provides for all women. Insulin therapy was initiated if fasting glucose and/or 1-h postprandial plasma levels remained elevated (>5.3mmol/l, >7.8mmol/l) respectively, at a 1-2-week re-evaluation.

From the data collected, 4,431 women were then divided into five groups denoting their GDM status: (1) 2851 women made up the ‘NGT group’: normal glucose tolerance with fasting glucose <5.1mmol/l and 2HG <7.8mmol/l, (2) 913 women made up the ‘WHO 1999 group’: GDM with fasting glucose ³7.0mmol/l and/or 2HG ³7.8mmol/l, (3) 1346 women made up the ‘WHO 2013 group’: GDM with fasting glucose ³5.1mmol/l and/or 2HG ³8.5mmol/l, (4) 667 women made up the ‘WHO 2013 only fasting group’: GDM according to new WHO 2013’ fasting threshold, but do not meet WHO 1999 criteria, and lastly (5) 234 women made up the ‘WHO 1999 only 2HG group’: GDM according to WHO 1999 2HG threshold, but do not meet WHO 2013 criteria.1 The primary endpoint was to assess the number of women diagnosed with GDM in relation to their characteristics and lifestyles. The secondary endpoint was to assess pregnancy and neonatal outcomes of each group. Continuous data was assessed using both unpaired t-test and Mann-Whitney U test, while categorical data was assessed using X2 or Fisher’s exact test.

Results showed that 22% of women had GDM according to WHO 1999 criteria, while 32% had GDM according to WHO 2013 criteria. Results also showed that women classified as having GDM, regardless of the old or new WHO guidelines, were more likely to develop gestational hypertension, preeclampsia, require a caesarean section or induced labor. Women in the ‘WHO 2013 only fasting group’ in comparison to women in the ‘NGT group’ were found to be older, had higher pre-pregnancy BMI (29.1kg/m2 vs 25.2kg/m2, P< 0.001), had more obesity (46.1% vs 28.1%, P< 0.001), smoked during pregnancy (13.2% vs 10.5%, P= 0.05) and had chronic hypertension (3.3% vs 1.2%, P< 0.001). The likelihood of gestational hypertension, planned caesarean section, and induced labor was also higher in the ‘WHO 2013 only fast group’ in comparison to the ‘NGT group” with results as follows: (7.8% vs 4.9%, p = 0.003), (10.3% vs 6.5%, p = 0.001) and (34.8% vs 28%, p = 0.001), respectively. The only statistically significant neonatal outcome reported for this group was an APGAR score <7 after 5 mins in comparison to the ‘NGT group’ (4.4% vs 2.6%, P=0.015) resulting in admission into the neonatology department (15% vs. 11%, P=0.04). Taking a look at the other experimental group, 79.5% of women in the ‘WHO 1999 only 2HG group’ were treated for their GDM with diet only modifications while 20.5% received added insulin therapy. In comparison to the ‘NGT group,’ women for the ‘Who 1999 only 2HG group’ were also found to be older, had higher pre-pregnancy BMI (26.4kg/m2vs 25.2kg/m2, P= 0.01), overweight (33.9% vs 23%, P< 0.001) and had hypertension (3% vs 1.2%, P< 0.02). This group showed a higher likelihood to have induced labor than the NGT group, (62.8% vs. 28%, P<0.001). As for neonatal outcomes, this had lower birthweights (3437± 498g vs. 3544± 579g, P=0.01) and were less likely to have macrosomic babies (12.8% vs. 20.9%, P=0.003) in comparison to the ‘NGT group.’

In conclusion, this study proved that if the more stringent criteria of the WHO 2013 were applied, there would be a 45% increase in GDM diagnoses. This could help prevent pregnancy-related outcomes associated with GDM. As a result of this study, Sarah Koning et al. recommends using a lower fasting glucose for the diagnoses of GDM.  Additionally, neonates belonging to either groups were more likely to have complications due to GDM. The main strength of this study is the large sample size giving it power.  Limitations include: generalizability and underestimation of data due to the lack of data for 1h glucose levels. Future studies should focus on generalizability and stricter glucose targets for GDM following 2HG OGTT.

Practice Pearls:

  • Stricter guidelines on gestational diabetes mellitus can potentially prevent pregnancy-related complications.
  • High-risk patients should be counseled on diet modifications to prevent added-insulin therapy.
  • Gestational diabetes puts mothers at risk for developing type 2 diabetes mellitus and infants at risk for neonatal complications.

Reference:

Koning, Sarah H., et al. “New diagnostic criteria for gestational diabetes mellitus and their impact on the number of diagnoses and pregnancy outcomes.” Diabetologia, 22 Nov. 2017, pp. 1-10., doi:10.1007/s00125-017-4506-x.

Adrianna Jackson, Doctor of Pharmacy Candidate: Class of 2018; LECOM College of Pharmacy