Notorious GDM

How gestational diabetes affects a mother and her unborn child

By Iris Thiele Isip-Tan, MD

Pregnant women will have lower sugar in the blood when they’re fasting, compared to non-pregnant women. That’s because of the uptake of blood sugar by the growing fetus and placenta.

After meals, blood sugar levels tend to go up in pregnant women. Hormones secreted by the placenta alter the action of insulin, a hormone responsible for the absorption of sugar in the blood. Pregnancy is a state of insulin resistance, where a woman’s pancreas will need to secrete more and more insulin as the pregnancy progresses, to keep the blood sugar at normal levels. For some pregnant women, this increase in insulin levels won’t be enough. Sugar will build up in the bloodstream, instead of being absorbed by the body. This condition is called gestational diabetes (GDM).

GDM is diabetes that is first recognized during the second or third trimesters of pregnancy. Risk factors for GDM include:

  • Age > 25 years old
  • Prior history of GDM
  • Sugar detected in the urine
  • Family history of diabetes
  • History of giving birth to babies weighing more than 8 lbs.
  • Diagnosis of polycystic ovary syndrome (PCOS)
  • Overweight or obese before pregnancy
  • Fetus that is large for age in the womb in the current pregnancy
  • Polyhydramnios (too much amniotic fluid) in the current pregnancy
  • Intake of drugs that alter carbohydrate metabolism (example: steroids)

GDM screening test

Pregnant women with GDM may exhibit no symptoms. Nevertheless, Filipino mothers are at increased risk of developing GDM. A study done by the ASEAN Federation of Endocrine Societies Study Group of Diabetes In Pregnancy (ASGODIP) found that 14.2% of Filipino women develop GDM during pregnancy. Universal screening is thus advocated by experts.

Expectant mothers with at least one of the risk factors mentioned above are considered high risk, and should undergo lab testing at the first prenatal visit. Women without any of the risk factors can undergo testing at the 24th to 28th week of pregnancy. Repeat testing is indicated in high-risk women who undergo testing in the first trimester with negative results. Women who come for a prenatal visit later in their pregnancy, should undergo testing even beyond the 28th week, if they haven’t been tested before.

A 75-gram oral glucose tolerance test (OGTT) is the recommended lab test to diagnose GDM. An OGTT with abnormal results in the first trimester of pregnancy may indicate undiagnosed diabetes before the pregnancy.

Sugar monitoring and diet

Most expectant mothers with GDM will only need lifestyle modification. A few will need insulin injections to keep their blood sugar at normal levels. Women with GDM will need regular prenatal checkups with a team composed of an obstetrician, endocrinologist and nutritionist.

The pregnant woman may be asked to monitor her blood sugar by finger pricking twice or as much as seven times a day. She will have to watch what she eats, as eating too little will compromise the growth of her fetus, and eating too much will lead to spikes in her blood sugar.

As blood sugar tends to spike after meals, the expectant mother will be advised to eat small frequent meals every three hours. She is allowed three main meals—breakfast, lunch and dinner—and three snacks in between. She should choose high-fiber food and include a good source of protein at every meal and snack.

A small breakfast is preferred, as blood sugar tends to go up in the morning. Fruits are allowed, except at breakfast. Non-caloric sweeteners are generally regarded as safe if taken in moderation. Concentrated sweets such as cake, jam, candy and softdrinks should be avoided.

The goal of management is good glucose control, to ensure that the fetus with normal weight is carried to term. Persistently high blood sugars in a pregnant woman increases the risk of overweight babies, which can increase the chances of birth injuries and Cesarean sections. A missed diagnosis of GDM can lead to intrauterine death of the fetus, or stillbirth. The risk of developing diabetes later in life also follows a baby born of a diabetic mother.

Other GDM-related risks

With GDM, the pregnant woman is at risk for pregnancy-induced hypertension and pre-eclampsia. While blood sugar levels may return to normal post-delivery, GDM can recur in a subsequent pregnancy.

The woman with a history of GDM has a 35% to 60% risk of developing Type 2 diabetes within 10 years. It’s recommended that a postpartum oral glucose tolerance test is done 4 to 12 weeks after delivery, to check if the blood sugar levels have gone back to normal. Should the postpartum OGTT be normal, the woman should still have her blood sugar tested every year for monitoring. If the woman develops prediabetes, intensive lifestyle modification with metformin is recommended, to delay progression to overt diabetes.

A woman with a history of GDM should be encouraged to lose weight. Breastfeeding is recommended for its beneficial metabolic effects for both the mother and baby. Ideally, the woman should be at normal weight and with normal blood sugar levels before her next attempt to get pregnant.

If you or someone you know is pregnant, ask your doctor or ask them about having an OGTT to screen for GDM. Remember, GDM begets diabetes for both mother and baby. HT