Share or recommend to a friend

Diabetes mellitus, or diabetes, is a chronic condition where the body is unable to produce any or enough hormone that regular blood sugar (glucose) levels resulting in excess amounts going around. This may sound all too familiar, but it is mainly because of the sobering statistic in Singapore and around the world.

According to the International Diabetes Federation (IDF), there are over 606,000 cases of diabetes in Singapore in 2017. It could be your mom, a friend, or a workmate who has it. However, beyond the numbers is a string of health concerns that comes with it and could potentially result into. When it affects a woman in a vulnerable state like pregnancy, it warrants immediate attention to ensure the safety of both the mom and the baby.

So, if you’re expecting or planning on getting pregnant soon, it’s important that you’re also aware of the type of diabetes that strikes during pregnancy. It pays to keep your guard up because any woman could potentially develop it.

  • What is Gestational Diabetes Mellitus?
  • What Causes Gestational Diabetes?
  • Who are at Risk for Gestational Diabetes?
  • What are the Potential Complications?
  • How is GDM Screening Done in Singapore?
  • Why is an HbA1c not advised when screening and diagnosing GDM?
  • How is GDM treated?

What is Gestational Diabetes Mellitus?

Gestational diabetes mellitus (GDM) is a type of diabetes that develops during pregnancy, usually during the second or third trimester. Those who develop it usually don’t have diabetes before pregnancy, but it also goes away after giving birth. However, some women go on to develop Type 2 diabetes later in life.

While it is true that any complication in pregnancy is a cause for concern, the good news is that gestational diabetes is controllable. Appropriate management through regular diet, exercise, and blood sugar-regulating hormone therapy lowers the risk of developing complications.

What causes GDM?

Our body has the type of hormone that keeps blood sugar levels in check. However, pregnancy hormones can interfere with how the body uses it. An example would be the increase of human placental growth hormone at 15 weeks of pregnancy which increases blood glucose levels.

Normally, the body responds by making more blood glucose-regulating hormone during pregnancy to meet the changing demands of the body. However, for some women, their system is unable to make enough of this hormone causing blood sugar levels to spike, eventually leading to GDM.

Who is at risk of GDM?

Women are considered high-risk candidates for GDM if they fall under any of these:

  • Have a pre-pregnancy BMI of more than 30kg/m2
  • Have a GDM history
  • Have pre-diabetes history
  • Have a history of polycystic ovary syndrome
  • Have delivered a baby that is 4kg and heavier
  • Woman is 40 years old or older

Women below the age of 40 can do an online diabetes risk assessment, here.

What are potential complications?

The main reason for controlling GDM is to avoid complications that can range from the mild to potentially fatal. It not only affects the mother, but the health and well-being of the baby even beyond the womb.


  • Pre-eclampsia (high blood pressure during pregnancy)
  • Preterm labor
  • Polyhydramnios (excessive amniotic fluid)
  • Miscarriage
  • Severe vaginal tears due to a large baby
  • Heavy bleeding after delivery
  • Risk of type 2 diabetes in the future


  • Premature birth
  • Stillbirth
  • Large for gestational age baby
  • Breathing problems
  • Jaundice (a condition where the skin, the whites of the eyes and mucuous membranes turn yellow)
  • Shoulder dystocia (an emergency when the head is delivered but the body is stuck)
  • Low glucose levels
  • Risk for childhood obesity
  • Risk of developing diabetes later in life

How is GDM Screening done in Singapore?

First Trimester

In Singapore, high-risk women are screened during the first trimester for undiagnosed pre-existing diabetes using non-pregnancy glucose thresholds. Click To Tweet

In Singapore, high-risk women are screened during the first trimester for undiagnosed pre-existing diabetes using non-pregnancy glucose thresholds. This is usually done around the 12th week prenatal visit together with routine pregnancy blood tests of infection screen, hemoglobin level and blood group. If results are normal, the woman is re-evaluated for GDM at 24-28 weeks of gestation.

24-48 Weeks

It is protocol that all women are screened for GDM within this period, including those who had normal results in the first trimester. It was found that there is increased resistance to the hormone that regulates blood sugar at this stage.

To ensure proper monitoring Universal screening is preferred over Risk-Based screening because Asians generally have a high incidence rate of GDM. This allows healthcare workers to detect more GDM cases and improve outcomes for the mother and the baby.

They do the test by using the 3-point 75g Oral Glucose Tolerance Test (OGTT). An OGTT requires you to drink a glucose solution after a night of fasting. This is followed by the extraction of a blood sample at the onset, one hour after, and then two hours later. A GDM diagnosis is made if any of the criteria below is met.

GDM Diagnostic Criteria

Plasma Glucose Levels (values are in mmol/L)Previous RecommendationsCurrent Recommendations based on IADPSG
FastingMore than or equal to 7.0More than or equal to 5.1
1-Hour Post-OGTTNot applicableMore than or equal to 10.0
2-Hour Post-OGTTMore than or equal to 7.8More than or equal to 8.5

Post Pregnancy

Post pregnancy screening serves as a follow-up for women with a history of GDM in a bid to monitor if their condition has resolved. It is expected that 6 weeks after delivery, blood glucose will revert to pre-pregnancy levels. To check if it does, a 2-point (fasting and 2-hr) 75 g OGTT will be done within 6-12 weeks after delivery using non-pregnancy normal values. The same screening process is also done on women who are diagnosed with pre-diabetes or diabetes in their first trimester.

Women who received hormonal treatment to control blood sugar levels during pregnancy, or those who have a high risk of developing diabetes (e.g. obese or family history of diabetes), are also required to have frequent follow-up check-ups. In fact, in Singapore, all women with a history of GDM must be screened for diabetes once every three years.

Why is HbA1c Not Advised When Screening and Diagnosing GDM?

HbA1c is a glycated hemoglobin which occurs when glucose in the blood sticks to hemoglobin, a protein within red blood cells. The test will reveal a person’s average blood sugar levels for the last 2-3 months.

It should not be used to screen or diagnose GDM because it is not sensitive in detecting high sugar levels after meals. HbA1c levels will not provide accurate results because it is also generally lower during pregnancy due to increased red blood cell turnover.

How is GDM Treated?

Treating GDM comes down to controlling blood sugar levels. This is accomplished through the following:

Eating Wisely

  • Be mindful of your carbohydrate intake
  • Choose food options that have low glycaemic index (e.g. wholegrain bread, sweet potato, low fat yogurt, vegetables)
  • Go easy on sugar
  • Watch your food portions
  • Eat meals on a regular basis to control appetite and blood glucose levels

Regular Physical Activity

Physical activity is particularly helpful in controlling blood sugar levels by redirecting resources. It increases the glucose needed by the muscles for energy. An active lifestyle also helps the body use hormones that regulate blood sugar levels more efficiently. To avoid injuries, be sure to do low-impact exercises that are tailored for pregnancy.


There are different medications that can help manage gestational diabetes, and they come in either oral or injectable form. Some oral medications reduce the amount of glucose the liver produces, while others stimulate the pancreas to produce more of the hormones that regulate blood sugar levels. Injectables are usually made out of hormone that allow glucose to enter the cells and be used for energy.

Take note that these medications must only be taken under medical advice. Like any other pharmacologic treatment, they still come with side effects and adverse reactions. 

Managing gestational diabetes mellitus improves outcomes for you and your baby. Expectant moms, or even those who are still planning on getting pregnant, should not discount the importance of coming into this journey prepared. So, if you have more questions, book a consultation so we can discuss in detail and start with the necessary tests.  

Dr Pamela Tan
About Dr Pamela Tan

Dr Pamela Tan is a board certified obstetrician and gynecologist in Singapore. She finished her undergraduate studies at the National University of Singapore and earned her post-graduate degree at the Royal College of Obstetricians and Gynaecologists in the UK. She is an accredited specialist by the Specialist Accreditation Board (Ministry of Health), and a fellow of the Academy of Medicine, Singapore. She subspecialises in colposcopy and is certified to perform Level 3 minimally invasive keyhole surgeries such as laparoscopic hysterectomy, myomectomy and cystectomy. Dr Pam also supports the natural birthing method and she strives to provide a personalised care and treatment for each patient.