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Gestational diabetes (GDM) is a common medical condition in pregnancy and affects 1 in 6 pregnancies and is potentially dangerous. GDM needs to be diagnosed early, monitored closely and treated appropriately. GDM can result in activation of certain fetal genes that have the capacity to set the baby on a life long road of obesity and predisposition to diabetes later in life (epigenetics). The life long risks of diabetes are important, but it is very important that mothers are aware that gestational diabetes has potentially serious effects on fetal well being in utero.
All pregnant women need to be tested for Gestational diabetes and when a diagnosis of GDM is made these women need to be monitored and treated closely.
Dr Steven will discuss how to reduce your risk of developing gestational diabetes.
This ideally should be done with pre pregnancy counselling, or in early pregnancy. Keeping your weight in a healthy range before pregnancy, maintaining an acceptable weight gain through pregnancy and exercising is very important in reducing your risks.
It is recognised that a family history of diabetes, obesity, excessive weight gain in pregnancy as well as other conditions such as polycystic ovarian syndrome (PCOS) will increase the risk of a mother developing GDM.
Diabetes in pregnancy is most commonly managed by dietary modification alone. Occasionally some women will require insulin treatment if dietary changes are inadequate to control their blood sugar levels. It is reassuring to note that GDM will almost always disappear after delivery of the baby and all treatment can be stopped after birth.
Dr Steven will keep you informed every step of the journey and he has written more information to read below on Gestational Diabetes.
Am I Going to Develop Gestational Diabetes?
Well, like so many disorders, there is a genetic predisposition to diabetes. Family history is an important part of the antenatal history taken at your first visit. Do you have a close family member, parent or a grandparent who has Juvenile onset diabetes or maturity-onset diabetes or a sibling who has had gestational diabetes?
There are also some other medical disorders which are connected with gestational diabetes, such as patients who have polycystic ovarian syndrome. This group of women have a much higher chance of developing gestational diabetes during pregnancy.
Obesity in Pregnancy and Diabetes Risk.
There is a second group of patients who don’t have a family history and don’t have any underlying predisposing medical conditions. Women with poor lifestyle habits are often overweight and therefore have a higher risk of developing gestational diabetes. They often develop a degree of insulin resistance. This can be made worse as their weight goes up in pregnancy and also because the placenta is producing placental steroids. The metabolic changes that happen in pregnancy can swing the pendulum towards developing diabetes as patients put on weight.
When do we screen for Gestational Diabetes
Gestational diabetes doesn’t usually develop early in pregnancy. For most patients it develops later on. A glucose tolerance test (GTT) is performed to diagnose Gestational Diabetes and it is usually performed between 26 to 28 weeks gestation.
If a patient has high risk factors such as a family history or if they have had gestational diabetes in a previous pregnancy or they have a history of polycystic ovarian syndrome, then we would recommend that the glucose tolerance test be performed at 16 weeks. If the early GTT is normal, then it would be repeated again at 26 to 28 weeks.
How to Avoid Risk of Developing Gestational Diabetes?
Avoiding gestational diabetes may not be possible for some women depending on their predisposing risk factors. Maintenance of an adequate weight gain through the pregnancy is one important way to reduce risk.
The next question would be, what is an adequate weight gain?. Well, it depends on what your initial weight was. Women within a good BMI have a greater degree of freedom to put on weight during pregnancy. Of course, an obese patient would have a very limited capacity to put on weight as that would increase her chances of developing diabetes,
What are the Symptoms of Gestational Diabetes?
Well, the problem is that pregnant women with GDM usually have no symptoms. Typically a medical student would be taught that the symptoms of diabetes are polydipsia and polyuria that is thirst and passing a lot of urine. In fact, in pregnancy because of the weight of the pregnant abdomen on top of the bladder, many pregnant women have urinary frequency anyway and thirst is strangely not common. So these signs and symptoms are not adequate predictors that someone has gestational diabetes.
Screening for GDM must be universal.
In the past, screening for diabetes was restricted to those women who had high-risk factors but this was unsatisfactory. If my recollection is correct, 60% of patients with gestational diabetes were being missed by screening only on the basis of high risk factors.
These high risk factors included women who were older, women who have had big babies in the past, and if they had pregnancy complications related to the size of the baby and also placental problems. Screening based on high risk factors was ineffective and now all pregnant women are tested at 26 – 28 weeks gestation. The principle is clearly to test everyone, identify those with GDM and start monitoring and treatment. This will significantly reduce risks.
Do I Need a Glucose Test at 16 weeks or 28 weeks?
Remember that a glucose tolerance test is performed on every pregnant patient. Sometimes we need to do an early glucose tolerance test at 16 weeks if a patient has a high-risk history, just to pick up the cases earlier in the pregnancy. If this early GTT is normal then these women should have another glucose tolerance test at 26 to 28 weeks.
What Can be the Consequences of Not Treating Gestational Diabetes?
Gestational diabetes is a very important factor for the health of the mother and baby because there are definitely risks. The first thing to note of course is that when someone has diabetes, they have high blood sugar. The high blood sugar passes across the placenta. When the baby receives high sugar levels, it has the capacity to increase its insulin levels. When fetal insulin levels increase, blood glucose will return to normal. Because the fetus can have high insulin levels it is prone to larger fluctuations in its blood sugars especially at night, which of course we would want to avoid.
High levels of insulin levels may send another signal to the baby’s brain to release growth hormone. Consequently the baby will now begin to grow at a faster speed. The primary problem however is not just that the baby grows faster than it should. A number of other important things are happening as well. The placenta grows larger as does the amniotic fluid around the baby. As a result of these and other changes the pregnancy is subject to a number of potential complications.
What are the Complications of Gestational Diabetes?
Well, first of all we can run through some of the potential complications that could develop from GDM. In a case of poorly controlled gestational diabetes it is common for the baby to be larger (macrosomic), and as mentioned earlier this can pose a problem when it comes to delivery.
Interestingly in some cases the muscle that separates the right side of the fetal heart from the left side of the heart can become much thicker, and this could affect blood flow through the cardiac valves of the baby’s heart.
Also as mentioned earlier, if the placenta becomes bigger, it can grow upwards and out of the way, but it has the potential to also extend downwards and into the lower segment of the uterus. If the placenta extends into the lowest segment of the uterus after 26 weeks, we call that a placenta previa, or a low lying placenta. This can be linked with episodes of unexpected and sometimes heavy bleeding. This can sometimes be heavy enough to warrant premature delivery of the baby.
I mentioned that the fluid around the baby increases the chances that the baby can adopt a malposition, that is being in a position other than being head down, which of course would then mean that there will be a greater need for a cesarean section delivery.
More than this, for the reasons already mentioned, a patient with diabetes can have a very big tummy which increases her chances of coming into premature labor or developing premature rupture of the membranes.
Finally, the strange thing is that when a woman has poorly controlled gestational diabetes, there is a link with a delay or an inadequate production of a special chemical that is involved in helping the lungs mature (surfactant). So these babies might be born prematurely, but they are born with immature lungs. Thus, a baby born to someone with gestational diabetes at any particular gestational age can behave poorly with regards to respiratory function compared to a baby born at the same age to a woman who did not have gestational diabetes.
There are a number of problems related to gestational diabetes beyond those that I have mentioned and these also include problems of placental function.
What to watch for after Birth
When the baby is born, we mustn’t forget that it might have high levels of insulin. So soon after birth, the baby needs to be fed early because otherwise it could develop hypoglycemia (low blood sugar levels). If the baby is premature, it may need to have a nasogastric tube which is a little tube up the nose and into the stomach to feed the baby. It might possibly require an intravenous drip to be able to treat the baby even better with intravenous fluids.
It should be very clear that the way to avoid complications is to test all mothers and when GDM is diagnosed, treat appropriately and of course monitor the baby. By so doing we can reduce or eliminate these risks.
Monitoring Blood Glucose Levels – Gestational Diabetes (GDM)
Women with GDM need blood sugar monitoring and this is done four times every day.
- Before breakfast
- Two hours after breakfast
- Two hours after lunch
- Two hours after dinner
Fasting blood sugar levels should be less than 5.1 millimoles per litre. Two hours after meals blood sugars should be kept within a range of 3.5 up to 6.7 millimoles per litre. If a woman has blood sugar levels above those cut-offs more than twice in a week at any particular time of day, she would be commenced on insulin.
It is so important to try and keep blood glucose levels under control. If this can’t be achieved with diet modification alone, then patients may need to start insulin treatment. We also need to monitor placental function and fetal growth with more ultrasound scans.
If diabetes is well controlled, patients’ risks are essentially the same as any other patient and they will be treated as a normal patient.
If blood sugars are only reasonably well controlled, I would recommend induction of labour in these women between 38 to 39 weeks. This decision would however be dependent upon blood sugar levels and also on the readiness of the cervix for induction.
If a patient’s diabetes is not under good control they will of course be on insulin treatment and I would recommend that they should be delivered around 38 weeks gestation or possibly even earlier.
Overview
Gestational Diabetes is common.
Most Women can control their blood sugar levels with diet alone. Some women will need to commence insulin therapy for the duration of their pregnancy. Complications are possible but usually occur with poorly controlled GDM. GDM disappears after pregnancy but women who have had GDM have a chance of developing Maturity onset diabetes later in life.
