# Gestational Diabetes Mellitus IADPSG Screening and Glycaemic Targets

> Gestational diabetes mellitus for NEET-PG Medicine: IADPSG 75 g OGTT thresholds, glycaemic targets, insulin versus metformin and postpartum diabetes testing.

- Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/gestational-diabetes-mellitus
- Exam / course: NEET-PG · Subject: Medicine
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-08
- Last updated: 2026-10-08
- Reference basis: Williams Textbook of Endocrinology; ADA Standards of Care in Diabetes; Williams Obstetrics
- How to cite: "Gestational Diabetes Mellitus IADPSG Screening and Glycaemic Targets", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/gestational-diabetes-mellitus

## Direct answer

Gestational diabetes mellitus is glucose intolerance first recognised in pregnancy that does not meet criteria for overt diabetes. It is usually diagnosed on a 75 gram oral glucose tolerance test at 24 to 28 weeks, where any single value at or above the one-step IADPSG threshold makes the diagnosis. Diet and exercise come first, with fasting glucose targeted below 95 mg/dL, and insulin is preferred if targets are not met.

## What you must remember

- **Screening timing:** high-risk women are tested early in pregnancy; others are tested at 24 to 28 weeks.
- **IADPSG thresholds:** fasting 92 mg/dL, 1-hour 180 mg/dL or 2-hour 153 mg/dL; any single value meets the diagnosis.
- **Glycaemic targets:** fasting below 95 mg/dL, 1-hour post-meal below 140 mg/dL and 2-hour post-meal below 120 mg/dL.
- **First line:** medical nutrition therapy and exercise, with home glucose monitoring four times daily.
- **Drugs:** insulin is preferred; metformin and glyburide cross the placenta but are used in some settings.
- **Fetal risks:** macrosomia, shoulder dystocia, neonatal hypoglycaemia and polyhydramnios.
- **Postpartum:** repeat OGTT at 4 to 12 weeks, then lifelong screening for type 2 diabetes.

## A 31-year-old with a macrosomic baby

A 31-year-old woman with a BMI of 27 and a previous macrosomic baby is screened early in pregnancy. The sequence of decisions is set out below.

1. **Screen early:** Her fasting glucose is 88 mg/dL, below the 92 mg/dL threshold, so a 75 gram OGTT is planned at 26 weeks.
2. **Apply the threshold:** The fasting value is 98 mg/dL, meeting the one-step threshold, and gestational diabetes is diagnosed.
3. **Start nutrition and monitoring:** Medical nutrition therapy is started with a dietician, and she checks glucose four times a day.
4. **Add insulin:** After ten days, fasting readings remain around 104 mg/dL and post-breakfast values reach 150 mg/dL. Bedtime intermediate-acting insulin is added, titrated to fasting and post-meal targets.
5. **Track the fetus and blood pressure:** Fetal growth is tracked with serial ultrasound, because macrosomia and polyhydramnios are the usual complications. Blood pressure and urinary protein are checked at every antenatal visit, because pre-eclampsia is more common in gestational diabetes.
6. **Retest after delivery:** Insulin is stopped after delivery and the neonate is monitored for hypoglycaemia. At 6 weeks postpartum, an OGTT confirms normal glucose tolerance, and she is told that her lifetime risk of type 2 diabetes is raised.

## Where the exam tries to catch you

Gestational diabetes questions hinge on a few points that candidates often miss.

- **Trap:** Using the wrong threshold. — **Correct:** A fasting value of 92 mg/dL is abnormal under the one-step IADPSG criteria, whereas older two-step criteria used a higher fasting cut-off, so the criteria applied must be named.
- **Trap:** Using HbA1c to diagnose gestational diabetes. — **Correct:** HbA1c is not used for that purpose, and a value of 6.5 per cent or more in the first trimester indicates overt, pre-existing diabetes.
- **Trap:** Assuming oral agents are as usable as insulin in pregnancy. — **Correct:** Insulin is the drug of choice because it does not cross the placenta in meaningful amounts, whereas the oral agents do cross it.
- **Trap:** Forgetting the postpartum OGTT. — **Correct:** It is the step that identifies women needing lifelong follow-up.

## Frequently asked questions

### Which glucose tolerance test and thresholds diagnose gestational diabetes?
A 75 gram oral glucose tolerance test is used, with the one-step IADPSG thresholds of 92 mg/dL fasting, 180 mg/dL at 1 hour and 153 mg/dL at 2 hours. Any single value at or above these levels makes the diagnosis. Indian national guidance (DIPSI) uses a non-fasting 75 gram load with a 2-hour value of 140 mg/dL or more, so the criteria should be stated.

### When should pregnant women be screened for gestational diabetes?
Women with risk factors such as obesity, previous gestational diabetes, a family history of diabetes or polycystic ovary syndrome are screened early in pregnancy. All other women are screened at 24 to 28 weeks. Early screening identifies overt diabetes that was present before pregnancy.

### Is insulin or metformin preferred for gestational diabetes?
Insulin is the preferred pharmacological treatment for gestational diabetes when diet and exercise fail. Metformin and glyburide cross the placenta and are used in some settings with acceptable outcomes. Insulin remains the agent with the most established safety profile.

### What postpartum test follows gestational diabetes?
A repeat 75 gram oral glucose tolerance test is recommended at 4 to 12 weeks after delivery in women with gestational diabetes. It identifies those with persistent diabetes or prediabetes. Lifelong screening for type 2 diabetes is recommended because the risk remains raised.