Put simply: Elevated blood sugars often occur in pregnancy and are commonly caused by gestational diabetes (GDM). Mothers with Type 1 diabetes and Type 2 diabetes are also likely to have elevated sugars if pregnant. Around 1 in 5 pregnant women (20%) develop GDM.
The more complex story: In pregnancy there many hormonal changes that occur in the mother in order to facilitate the growth of a baby. Many of these changes are caused by hormones produced by the placenta. Some of these hormones cause the mother’s insulin receptors to become resistant to insulin. Insulin is a chemical that acts like a key, and when bound to the insulin receptor on a cell surface, the lock, opens a channel for the movement of sugar from the blood into cells.
If a person is insulin resistant, then they require more insulin to open the lock and transport sugar (or glucose) out of the blood and into the cell. This is the same process that causes type 2 diabetes.
As the placenta grows in pregnancy, more and more hormones are made and released to support the growth of baby. This makes the mother more and more insulin resistant. At some point the mother may not be able to produce enough insulin to overcome the resistance, and if this occurs blood glucose levels rise.
High glucose levels readily cross the placenta and expose the baby to this diabetic state.
Certain women are at a much higher risk and should be screened before becoming pregnant, at 12 weeks’ gestation and again at 24-28 weeks if not previously diagnosed. High risk factors for gestational diabetes include
The Glucose tolerance test is performed by presenting to a testing facility in a fasted state. A blood test is taken followed immediately by consuming a sugary drink (75g glucose). Further blood tests at 1 hour and 2 hours need to be taken and the person being tested should remain inactive during the testing process.
|Fasting glucose||1 hour glucose||2 hour glucose|
|5.2 mmol/l or more||10.0 mmol/l or more||8.5 mmol/l or more|
|92 mg/dl or more||180 mg/dl or more||153 mg/dl or more|
Complications that can happen to the baby include being bigger at birth with the associated risks of a delivery from a large baby. Babies are also likely to be more immature and can have breathing difficulties after birth as well as experiencing very low blood sugar levels. In the long term a child exposed to high blood sugar levels during gestation is more likely to be overweight and develop diabetes once an adult.
Complications to the mother include a difficult delivery and a high chance of having a caesarean section. The mother is also more likely to have problems with blood pressure and in an extreme situation can develop life threatening seizures from a condition known as eclampsia.
Safely controlling sugars minimises the chance of this happening.
50% of mothers with gestational diabetes will go on to develop type 2 diabetes later in life and this is more likely if the correct lifestyle changes are not undertaken. If a mother with previous gestational diabetes becomes pregnant again then the next pregnancy should always be considered high risk for subsequent diabetes and be tested for early in pregnancy.
These modifiable risk factors are the best place to start when planning pregnancy. Some of this is around diet and weight management and is part of Preparing for Pregnancy.
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