Gestational Diabetes Mellitus – Part 2

Once gestational diabetes mellitus (GDM) is diagnosed, it is important for the woman to start controlling her blood glucose (sugar) levels in order to reduce the risks of uncontrolled high blood glucose levels both to the mother and the baby.

We will first look at why it is important to control the mother’s blood glucose levels.

Importance Of Controlling The Mother’s Blood Glucose Levels

The mother and the baby’s blood circulatory systems are linked via the placenta. If the mother’s blood glucose levels are high, the high blood glucose will pass through the placenta into the baby’s circulatory system and causes the baby’s blood glucose levels to become high as well.

High blood glucose levels in the baby can have adverse impact on the baby. The adverse events can happen both before the baby is delivered as well as after the delivery.

High blood glucose levels in the mother may also cause adverse outcomes in the mother for the remainder of the pregnancy.

Impact Of High Blood Glucose Levels To The Baby

1. Macrosomia (increased size and weight of the baby)

High blood glucose levels in the baby directly stimulates the baby’s pancreas to produce more insulin. High levels of insulin in the baby will stimulate growth of the baby and will cause the baby to grow bigger at a faster rate.

The increased in growth in the baby caused by high blood glucose levels tends to be disproportionate – with higher increase in size of the baby’s abdomen compared to the other parts of the baby’s body.

The increased size and weight of the baby will pose a challenge if natural vaginal delivery is planned. There is a risk of the baby getting stuck in the birth canal in the middle of delivery due to the increased size of the baby’s torso – a condition known as shoulder dystocia.

If shoulder dystocia does occur during delivery, there is an increased risk of injury to the nerves of the arms when the doctor (obstetrician) tries to deliver the baby.

Sometimes, if the baby really grows too big for normal vaginal delivery, the doctor (obstetrician) may advise for cesarean delivery instead.

2. Polyhydramnios (increased amount of amniotic fluid)

Increased blood glucose levels in the baby will increase the baby’s urine output. This will result in polyhydramnios – increased amount of fluid in the amniotic sac (the sac in the womb which the baby develops in).

Polyhydramnios can lead to premature contractions of the uterus and possibly preterm labor. Other possible problems include premature rupture of membranes (with possible risk of infection and slipping out of the umbilical cord) and sudden fetal death.

3. Post-delivery medical issues for the baby

After delivery of the baby, there are still potential medical issues that may occur in the baby.

If the mother’s blood glucose levels are high in the one to two weeks before delivery, the baby has a risk of developing low blood glucose level after birth. This is because the baby’s pancreas will already be producing more insulin due to the high blood glucose levels.

Immediately after delivery when the umbilical cord is cut, the baby will still have high levels of insulin in the body. But because the baby is not longer receiving blood (with high glucose levels ) from the mother, the baby’s blood glucose levels will drop with the high levels of insulin.

It will take up to 3 days for the high levels of insulin to be cleared from the baby’s body, during which time the baby may need treatment for low blood glucose levels.

Other potential medical issues that can affect the baby post-delivery include:

  • Respiratory (breathing) problem that may require breathing support
  • Higher risk of jaundice (yellowing of the skin and eyes)
  • Increased risk of stay in the intensive care unit (ICU)

Impact Of High Blood Glucose Levels To The Mother

High blood glucose levels which are not controlled in the pregnant woman can result in her blood pressure increasing higher than normal – gestational hypertension. If this occurs, the woman will need to take medications to control her blood pressure.

There is also increased risk of pre-eclampsia – a condition which includes both high blood pressure and protein leakage in the urine. Pre-eclampsia in the pregnant woman can lead to problems such as:

  • Growth restriction in the baby – the baby having lower than normal weight due to inadequate blood supply to the placenta
  • Preterm birth
  • Placental abruption – a condition in which the placenta separates from the inner wall of the uterus before delivery, increasing the risk of heavy bleeding
  • Eclampsia – a condition which includes pre-eclampsia and seizures (fits) in the mother


The risks of uncontrolled GDM to both the pregnant mother and the baby are real.

These risks can be reduced or even eliminated if the mother’s blood glucose levels are controlled via dietary modifications and/or medications.

In the next part, we will talk about the management of GDM – blood glucose monitoring, dietary changes and medications.