What Is Gestational Diabetes?

During pregnancy, your body goes through major hormonal and metabolic changes.

One of those changes affects insulin—the hormone that helps glucose move from your bloodstream into your cells.

As pregnancy progresses, hormones produced during pregnancy can make the body less responsive to insulin. Your pancreas usually compensates by producing more insulin.

When the body cannot produce enough insulin to meet this increased demand, blood glucose can rise.

This may lead to gestational diabetes mellitus, or GDM.

GDM is important because elevated glucose during pregnancy can affect both maternal health and the developing baby.

But there is another important reason screening matters:

You may have gestational diabetes and feel completely well.

It is therefore not something that can reliably be identified from symptoms alone.

Nearly 1 in 4 Pregnant Women in India: What the New ICMR Study Found

One of the most important recent Indian studies on gestational diabetes comes from the ICMR-INDIAB national study (ICMR-INDIAB-24), published in the Indian Journal of Medical Research in 2025.

The researchers analysed pregnant women participating in the nationwide ICMR-INDIAB survey, which covered 31 States and Union Territories across different phases between 2008 and 2024.

Of 1,206 pregnant women identified, 1,032 women with usable glucose-testing information and without overt diabetes were included in the GDM analysis.

Why Is Early Pregnancy Screening Becoming So Important?

Gestational diabetes has traditionally been strongly associated with testing at around 24–28 weeks of pregnancy.

That remains an important screening period.

But the ICMR-INDIAB-24 findings add an important Indian perspective.

The weighted prevalence of GDM among women assessed before 20 weeks was 19.2%.

In other words, a substantial amount of abnormal glucose metabolism was already detectable earlier in pregnancy.

The researchers concluded that there is a need for screening all pregnant women for GDM starting in early pregnancy.

Should Every Pregnant Woman Be Screened?

Indian guidance has supported a universal approach to GDM screening rather than relying only on obvious risk factors.

This matters because gestational diabetes can occur even when a woman does not appear to be at particularly high risk.

The ICMR-INDIAB-24 study strengthens this argument by showing a substantial burden across both urban and rural India.

In that study, the difference between urban prevalence (24.2%) and rural prevalence (21.6%) was not statistically significant.

This is an important public-health message.

Gestational diabetes should not be thought of as only an urban, affluent or metropolitan pregnancy problem.

Are Some Women More Likely to Develop Gestational Diabetes?

Yes. Certain characteristics may increase the likelihood of GDM.

Risk factors discussed in clinical literature include:

• A previous pregnancy affected by gestational diabetes
• A family history of diabetes
• Overweight or obesity
• Increasing maternal age
• Previous delivery of a large baby
• Polycystic ovary syndrome (PCOS)
• Previous pregnancy-related complications in some circumstances
• Other metabolic risk factors

In ICMR-INDIAB-24, family history of diabetes and higher systolic blood pressure were independently associated with higher GDM risk.

A family history of diabetes was associated with an adjusted odds ratio of 2.16.

However, having no obvious risk factor does not guarantee that gestational diabetes will not occur.

This is one reason universal screening can be valuable.

What Actually Happens During a Gestational Diabetes Test?

The exact procedure depends on the testing protocol being followed.

A common approach uses a measured glucose drink containing 75 g of glucose.

Depending on the protocol, the process may involve:

1. A blood glucose measurement before drinking glucose.
2. Drinking a standard glucose solution.
3. Waiting for a specified period.
4. One or more additional blood samples to see how your body handles the glucose load.

Some Indian screening protocols use a single 2-hour blood glucose measurement after 75 g glucose.

Other protocols measure fasting glucose as well as glucose one and/or two hours after the drink.

This difference is important because the tests are not interchangeable simply because they all involve glucose.

Do You Need to Fast Before Gestational Diabetes Testing?

It depends on the protocol your healthcare provider or laboratory is using.

This is one of the most confusing aspects of gestational diabetes screening.

Under the Government of India/DIPSI-style approach, a 75 g glucose load may be given irrespective of the timing of the woman's last meal, followed by measurement of plasma glucose after two hours.

Other approaches, including a conventional oral glucose tolerance test, may require an overnight fast and multiple blood samples.

Why Do Different Websites Show Different GDM Cut-Offs?

If you search online for gestational diabetes glucose values, you may find several different numbers.

This does not necessarily mean one source is wrong.

Different professional bodies and health systems use different diagnostic approaches.

For example, the Indian DIPSI-style single-step approach commonly uses a 75 g glucose load followed by a two-hour plasma glucose measurement, with 140 mg/dL or higher used as the GDM threshold.

Other international approaches use fasting, one-hour and/or two-hour measurements with different thresholds.

The importance of the diagnostic method is clearly demonstrated by ICMR-INDIAB-24.

The lesson for a patient is not to choose a cut-off from the internet.

Your result needs to be interpreted according to the exact test and diagnostic criteria being used by your healthcare team.

Why Does Gestational Diabetes Matter?

Most women with GDM can be supported effectively once the condition is recognised.

But untreated or inadequately managed high blood glucose during pregnancy can increase the likelihood of pregnancy and delivery complications.

Depending on individual circumstances, these can include increased likelihood of:

• Having a larger-than-expected baby
• Complications during delivery
• High blood pressure disorders during pregnancy
• Caesarean delivery
• Low blood glucose in the baby after birth
• Other pregnancy and newborn complications

This does not mean that receiving a GDM diagnosis means these complications will happen.

The purpose of screening is exactly the opposite—to identify elevated glucose so that appropriate monitoring and management can begin.

What Happens If Gestational Diabetes Is Detected?

A GDM diagnosis does not mean you have failed at pregnancy or that you have necessarily done something wrong.

Pregnancy itself produces major metabolic changes, and some women are simply less able to compensate for the increased insulin resistance.

Your healthcare team may recommend a combination of:

• Blood glucose monitoring
• Individualised nutrition guidance
• Appropriate physical activity where medically suitable
• Monitoring maternal weight and blood pressure
• Additional monitoring of the baby's growth
• Medication or insulin when needed
• Planning for delivery according to your individual circumstances

The exact plan depends on your glucose levels, stage of pregnancy, medical history and response to treatment.

Do not make major dietary changes or begin, stop or alter diabetes medicines during pregnancy without discussing them with your healthcare provider.

Does Gestational Diabetes Mean You Should Stop Eating Carbohydrates?

No.

Pregnancy is not the time to independently adopt an extremely restrictive diet simply because your glucose result is high.

Carbohydrate quantity, quality and distribution across meals can influence blood glucose, but pregnancy also requires adequate nutrition for both mother and baby.

Your healthcare provider or qualified dietitian may help you develop a meal pattern appropriate for your glucose levels, nutritional needs and pregnancy.

Does Gestational Diabetes Disappear After Delivery?

For many women, blood glucose improves after the baby is born as pregnancy-related hormonal changes resolve.

But that is not the end of the story.

Having gestational diabetes is associated with an increased future risk of developing Type 2 diabetes.

Your healthcare provider may therefore recommend glucose testing after delivery and continued diabetes screening in the years that follow.

This makes your history of GDM an important part of your long-term medical history—even if your glucose returns to normal after pregnancy.

Questions Worth Asking Your Doctor

At your antenatal appointment, consider asking:

• When should I be screened for gestational diabetes?
• Do I need testing in early pregnancy?
• If my early test is normal, will I need another test at 24–28 weeks?
• Which gestational diabetes test are you ordering?
• Do I need to fast before the test?
• What glucose drink and blood sampling schedule will be used?
• Which diagnostic criteria are being used to interpret my result?
• What does my result mean for the rest of my pregnancy?
• Will I need to monitor my glucose at home?
• Should I meet a dietitian or diabetes specialist?
• Will my baby need additional monitoring?
• When should my blood glucose be checked after delivery?
• How often should I be screened for diabetes in the future?

What Should We Learn From the ICMR-INDIAB-24 Study?

The study gives India something it previously lacked: a nationally representative estimate of gestational diabetes prevalence.

Three findings deserve particular attention.

1. GDM Is Common

Using NICE criteria, the estimated national weighted prevalence was 22.4%—nearly one in four pregnant women.

2. Many Cases Were Not Previously Known

Newly detected GDM accounted for 19.8 percentage points of the overall 22.4% prevalence.

This demonstrates why screening matters even when there has been no previous diabetes diagnosis.

3. Early Pregnancy Matters

The study estimated an early-GDM prevalence of 19.2% before 20 weeks.

That challenges the idea that gestational glucose problems become relevant only around the traditional 24–28-week screening period.

The study also observed an apparent increase in GDM prevalence across different ICMR-INDIAB study phases—from 13.3% during 2008–10 to 30.2% during 2019–20.

This should be interpreted as a trend across study phases rather than as a precise year-by-year national incidence estimate.

Frequently Asked Questions

What is gestational diabetes?

Gestational diabetes mellitus (GDM) refers to high blood glucose first detected during pregnancy in a woman who does not already have overt diabetes. Pregnancy-related hormonal changes can increase insulin resistance and make it harder for the body to keep glucose within the desired range.

When should I be tested for gestational diabetes?

Screening may begin during early pregnancy or at the first antenatal contact. If early testing is normal, your healthcare provider may recommend testing or repeat testing later, commonly around 24–28 weeks, depending on the protocol and your clinical circumstances.

Do I need to fast for a gestational diabetes test?

Not necessarily. Fasting requirements depend on the test being used. Some Indian protocols allow a 75 g glucose test irrespective of the timing of the last meal, while other oral glucose tolerance tests require fasting. Follow the instructions given by your healthcare provider or laboratory.

What does the 75 g glucose test involve?

You drink a solution containing 75 g of glucose and have your blood glucose measured according to the protocol being used. Some protocols use a two-hour measurement, while others use fasting and additional timed measurements.

Does a two-hour glucose value of 140 mg/dL mean GDM?

A two-hour value of 140 mg/dL or higher is used as the diagnostic threshold in the Indian DIPSI-style approach. Other diagnostic systems use different fasting and post-glucose thresholds, so your result must be interpreted according to the specific test you underwent.

Why does Diafemme say nearly 1 in 4 pregnant women in India may have GDM?

The ICMR-INDIAB-24 national study estimated a weighted GDM prevalence of 22.4% using NICE diagnostic criteria. The estimated prevalence changed when other diagnostic definitions were applied, so the testing criteria should always be stated alongside this figure.

Can gestational diabetes occur before 20 weeks?

Yes. ICMR-INDIAB-24 estimated an early-GDM prevalence of 19.2% among women assessed before 20 weeks, supporting the importance of considering glucose screening from early pregnancy.

Can I have gestational diabetes without symptoms?

Yes. Many women with gestational diabetes do not experience obvious symptoms. This is one of the reasons routine screening during pregnancy is important.

Does gestational diabetes mean I will have diabetes forever?

Not necessarily. Glucose levels often improve after delivery, but a history of GDM increases the future risk of Type 2 diabetes. Postpartum testing and continued long-term screening are therefore important.

Diafemme's Takeaway

Gestational diabetes screening is not simply another pregnancy test.

It is an opportunity to identify a metabolic change that may otherwise remain invisible.

The latest nationally representative Indian evidence makes that particularly relevant: using NICE criteria, 22.4% of pregnant women in ICMR-INDIAB-24 had GDM, and elevated glucose was also identified early in pregnancy.

But one number should never create unnecessary fear.

Different diagnostic methods produce different prevalence estimates and use different glucose thresholds.

What matters to you is understanding which test you are having, when you should have it, whether you need to fast, and how your healthcare provider will interpret the result.

At Diafemme, we believe pregnancy screening should leave you better informed—not more anxious.

Know the test. Understand the result. Ask the right questions.