What is Gestational Diabetes & Its Effects on Unborn Babies

What is Diabetes?

Most of us before becoming pregnant have heard of Type-1 and Type-2 Diabetes Mellitus, but don’t necessarily know what they are. Then, once pregnant, we are usually told that peeing on a little urinalysis stick each time we visit our midwife, assists to ensure we’re not acquiring Gestational Diabetes. But all in all, it can feel like a pretty confusing topic. So let me try to demystify the mysterious!

DM (Diabetes Mellitus) is primarily an insulin related disease, and insulin is the hormone that enables our body’s cells to convert blood sugar (glucose) into energy.

But here’s the big problem in Diabetes … When our energy levels are low, the body releases more and more sugar into the blood to feed the “starving” cells – not realising that the problem is not the lack of blood sugar, but actually the lack of Insulin to covert the sugar into energy. This results in high blood sugar (called hyperglycaemia), which can wreak irreparable damage, especially to blood vessels.

Type-1 Diabetes is when a person is born with an inability to produce enough insulin, and it is typically diagnosed in childhood or adolescence, and treated by supplementing their body’s insulin supply through injections.

Type-2 Diabetes is traditionally associated with old age due to inadequate insulin production and/or increased insulin resistance. However, in today’s Western often overly rich dietary lifestyle and obesity, Type-2 is occurring in younger generations.

Type-3 Gestational Diabetes is a unique phenomenon within the physiology of pregnancy:

Pregnancy hormones increase the mother’s insulin resistance, to increase the energy available to the baby. This results in the mother’s insulin levels to double by the 3rd trimester! But, if the pregnant woman’s body is unable to produce enough insulin to keep up, then she develops high blood sugar (hyperglycaemia).

How is Gestational Diabetes diagnosed & treated?

One sign is glucose in urine. Our kidneys filter (clean) our blood, producing our urine. But when the tiny blood capillaries of the kidneys become damaged from the sugar-rich blood, some of the sugar molecules leak into the urine. So that is why us midwives all ask our pregnant women to pee on a urinalysis stick at their antenatal appointments.

As an extra double-check for undiagnosed Gestational Diabetes, at around 24-28 Weeks pregnant, midwives offer women a Polycose screening test for Diabetes. This involves the Laboratory taking a blood sample on arrival, consuming a sugar-drink, then re-testing the blood an hour later:

  • If the results come back with slightly elevated blood sugar levels, then the test may be repeated in 3-4 weeks.
  • If the results come back with higher than normal levels, then a 12-hour fasting diagnostic GTT (Glucose Tolerance Test) will be recommended.
  • If the results come back with alarmingly high blood sugar levels, or if the GTT test result is positive, then the LMC must recommend the woman receives a referral consultation with a DIP Team (Diabetes in Pregnancy team).

Dependent on circumstances, the LMC may completely hand over primary care to these secondary services, or the LMC may assume the main responsibility of care, supported by the DIP Team.

The Diabetes in Pregnancy team will educate the woman on diet, exercise, and the management of her blood sugar level monitoring. Some pregnant women are able to control their blood sugar levels through diet alone. Other pregnant women’s bodies will become insulin-dependent requiring regular insulin injections (just while they’re pregnant).

How does Diabetes affect the baby?

The unique problem during pregnancy of untreated or poorly controlled diabetes, is that although maternal blood sugar crosses the placenta, maternal insulin does not. So, all babies produce their own insulin for converting blood sugar into energy. But with such sugar-rich maternal blood, this results in the baby having high blood insulin levels.

Unfortunately, Insulin is also a growth hormone, so this then increases the baby’s muscle growth and fat stores, resulting in a large cherub-like baby (called macrosomia).  Alternatively, or additionally, the large baby’s increased consumption of oxygen can lead to a chronic lack of oxygen (fetal hypoxia) resulting in a growth-restricted and/or ruddy-red appearing baby, due to an increased production of red blood cells (called polychythaemia).

From the pregnant mother’s perspective, diabetes in pregnancy can also manifest as polyhydramnios (large amounts fluid around baby); and an increased risk of shoulder dystocia at birth (shoulders stuck after the head is delivered).

The baby’s high levels on insulin also inhibit their lungs maturing as they should, resulting in a newborn at risk of respiratory distress requiring to be admitted to the baby hospital (NICU or SCBU).

Another complication for the newborn baby, is combining their own insulin-rich blood at birth with being instantly disconnected from their mother’s sugar-rich blood, as this can rapidly plunge a newborn into dangerously low levels of blood sugar. So newborns of diabetic mothers, have their blood sugar levels checked every few hours, until they have been stable for around 12 hours.

These babies also have an increased risk for severe jaundice and umbilical bleeds, so additionally recommended can be Vitamin-K at birth, and close monitoring for Jaundice complications during the first days.

Urban Myths

  • Infants of pregnant mothers who have diagnosed and well controlled diabetes can be healthy normal babies.
  • Infants of pregnant mothers with undetected or poorly managed diabetes, are at higher risk of diabetes, obesity (and even lower IQ) – though these may also be family obesity lifestyle related.
  • All pregnant women are at risk of Gestational Diabetes. However, those who are at increased risk include women with a family history of Diabetes; a pregnancy history of Gestational Diabetes; hypertension (high blood pressure); obesity; multiple pregnancy (eg twins); and particular ethnicities (especially Maori, Pacific Island, Indian and Chinese).

After childbirth a woman no longer has Gestational Diabetes. However she is at increased risk later in life of developing Type-2 Diabetes, so should consider having a Glucose Tolerance Test every couple of years.

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