Diabetes mellitus is becoming a big health issue all over the world, not just in the general population but also in pregnant women. The screening for gestational diabetes and the latest management guidelines from the government of India, NICE, ACOG and  ADA  are penned down in this article.

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Screening

Who should go through the screening?

According to the American Diabetes Association ADA, screening should be done only for high-risk cases listed below: 

1. Body mass index of more than 30 kg/m2.
2. Previous macrosomic baby weighing 4.5 kg or more.
3. Previous gestational diabetes.
4. Family history of diabetes.
5. Family origin with a high prevalence of diabetes. South Asian (specifically women whose country of family origin is India, Pakistan or Bangladesh),  Middle Eastern (specifically women whose country of family origin is Saudi Arabia, United Arab Emirates, Iraq, Jordan, Syria, Oman, Qatar, Kuwait, Lebanon or Egypt).
6. Clinical conditions associated with insulin resistance like PCOD.

When to screen? 

FOGSI recommends screening every pregnant woman at the 1st visit using the DIPSI guidelines

DIPSI (diabetes in Pregnancy Study Group India): A single-step procedure irrespective of the last meal. Pregnant women attending the antenatal OPD were given 75g anhydrous glucose in 250-300ml of water and plasma glucose was estimated after 2 hours. This single-step screening method is recommended by both FOGSI and FIGO.

Criteria In Pregnancy Non-Pregnant

• 2hr > 200mg/dl DM
• 2hr > 140mg/dl GDM IGT
• 2hr > 120mg/dl DGGT

DM- diabetes mellitus, DGGT- Decreased gestational glucose tolerance, IGT- Impaired glucose tolerance

World Health Organisation (WHO Screening ):  75g 2hr Oral glucose tolerance test (OGTT).

Two blood samples are taken

1. Fasting blood sample: 75g glucose is diluted in 250- 300ml water is ingested
2. Two hours post glucose: Venous plasma glucose of ≥140 mg/dl (7.8mmol/l) at 2-hour is classified as having GDM.

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Management

During pregnancy, the fetus is dependent on the mother for nutrition and ultimately gets affected in case of gestational diabetes mellitus (GDM). There are various abnormalities a fetus can develop, from congenital malformations, Intra-uterine growth restrictions(IUGR), macrosomia or other organs/growth problems, and even stillbirth/Intra-uterine fetal death(IUFD).

Fetal macrosomia, in 3 trimesters is also a prominent feature of diabetic fetopathy. Birth weight is usually more than 4 kg. Shoulder dystocia, birth injuries and neonatal asphyxia are common occurrences in such cases, adding to maternal and perinatal morbidity and sometimes mortality. Maternal euglycemia has to be the aim for the prevention/alleviation of many of these complications.

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Guidelines for Management

A) Government of India guidelines :

1. Once GDM is diagnosed, the mother is advised MNT. It consists of meals where carbohydrate intake is controlled. There is an optimisation of nutrition to meet the nutrition needs of the mother and the foetus. The plan includes energy appropriate for optimum weight gain and maintenance of normal glucose levels. An appropriate exercise regime is advised.
2. When on MNT, blood glucose 2 hours after a meal (PPBS) is checked after 15 days. If PPBS is maintained at less than 120mg/dl, she is asked to continue on MNT and exercise.
3. If the PPBS is not maintained at <120mg/dl and she is less than 20 weeks pregnant, insulin therapy is started. When on insulin therapy, blood sugar is monitored every third day or frequently. The target levels are fasting blood glucose (FBS) less than 95 and PPBS less than 120mg/dl.
4. If the woman is more than 20 weeks gestation and her PPBS is more than 120mg/dl, she is started on metformin. When on metformin, blood sugars are tested twice a week.
5. Metformin is started at 500m/day twice daily and is increased up to 2 gm/day until blood sugar control is obtained. The advantages of metformin over insulin is the reduced maternal weight gain and incidences of hypoglycemia.
6. If blood sugar target levels are not obtained with metformin, injection of insulin is added.
7. If the two-hour PPBS is very high at the initial diagnosis of GDM, Insulin is started at once.

B) NICE Guidelines :

1. According to the National Institute for Health and Care Excellence NICE Guidelines, GDM is diagnosed when there is a fasting plasma glucose level of 5.6mmol/L or a 2-hour plasma glucose level of 7.8mmol/L.
2. Once the diagnosis of GDM is made, the patient is advised diet therapy and exercise. The patient is reviewed after 1-2 weeks.
3.  If the target levels are not met, oral metformin or insulin therapy is initiated.
4. Insulin is started at once if there is a contraindication or if the patient is not interested in metformin therapy. If target levels are not attained on metformin therapy, insulin is added.
5. Glyburide is initiated if there is intolerance to metformin or the patient refuses insulin therapy and is not controlled on metformin therapy.
6. Immediate initiation of insulin therapy:

• If fasting glucose level is more than 7.0mmol/L at diagnosis.
• If fasting glucose level is between 6.0 and 6.9mmol/L and there is macrosomia or hydramnios.

C) American College of Obstetricians and Gynaecologists (ACOG) Guidelines : (2013)

Once a diagnosis of GDM is made, the patient is advised nutrition therapy. If target levels are not achieved, insulin therapy is initiated. Glyburide or metformin can also be tried as first-line therapy.

D) American Diabetes Association (ADA) Guidelines : (2016b)

1. Insulin is to be considered as first-line drug therapy in GDM. Glyburide is associated with an increased risk of macrosomia and neonatal hypo glycemia. Metformin can be tried in GDM but has a higher risk of prematurity and the unknown long-term effects on the foetus are of concern. Metformin crosses the placenta.
2. In the metformin in GDM trial (MiG) of 2008, metformin is compared with insulin in the treatment of GDM. There is no great difference between the therapies concerning the neonatal outcomes. Preterm deliveries and the risk of severe neonatal hypo glycaemia are found more in the metformin group. 45% of women in the metformin group needed additional insulin therapy for glycemic control.
3. In the study by Moore et al in 2010 ,metformin and glyburide therapies are compared. In this study, the patients on metformin required additional insulin for blood sugar control. A comparative study on metformin therapy versus insulin has been conducted
4. by Balsells in 2015 . In this study, metformin therapy is associated with lesser maternal weight gain and lesser pregnancy-induced hypertension. But the foetal effects are increased preterm deliveries, lower age of the foetus at delivery and decreased incidence of neonatal hypo glycemia with metformin usage.
5. Supplemental insulin for glucose control is needed in 33.8% of the patients.

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Conclusion

Metformin is used with caution as it crosses the placenta and the long-term effects on the foetus are not clear. Glyburide is associated with a higher chance of neonatal hypo glycemia. Both the oral drugs are less effective if the fasting blood glucose levels are high at diagnosis or if GDM is diagnosed before 26 weeks of pregnancy.The above factors need to be considered before the initiation of therapy in patients with GDM.

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Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India. Dr Komal Chavan is a Medical Director and Senior Consultant from Mumbai.