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Gestational diabetes

by Dr. Vijith Vidyabhushana, Consultant Obstetrician and Gynaecologist, Colombo South Teaching Hospital, Kalubowila.

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Risks during pregnancy?

Gestational diabetes is more common in women who are overweight but may develop in other situations. These include:

* Gestational Diabetes in a previous pregnancy
* A large baby in a previous pregnancy (over 3.5 kg)

* An unexplained stillbirth (delivery of a dead baby)

* Being over 35 years old

* Family history of diabetes (one first degree relative - Mother, father, brother or sister)

* Physically inactive

* High blood pressure

* High cholesterol

* Women with Polycystic ovary syndrome

* Women with a history of cardiovascular disease (Diseases of heart and blood circulation)

Screening and diagnosis Screening test: 'Screening' is a method of finding out those who are at a high risk of getting a particular condition. Screening test 'positive' does not mean that she is having the condition screened for.

A further test has to be done to confirm the condition that we are going to diagnose. Screening is done mostly when it is a health problem which can be asymptomatic. Because gestational diabetes may be asymptomatic but have serious consequences that can be reduced by treatment, it is a candidate for screening.

The screening test for diabetes is a test of urine to check for sugar which is done in each and every clinic visit. Presence of sugar in urine does not mean that you are having diabetes.

Due to hormonal changes in pregnancy the blood supply to kidneys increase and therefore more sugar will be filtered from blood in to urine and this condition is called 'Renal Glycosurea' which means appearance of sugar in urine due to increased blood supply to the kidney in pregnancy.

This condition is seen in some pregnant women and it is completely normal.

To arrive at a diagnosis of renal glycosurea one has to exclude gestational diabetes. Some use a blood sugar test two hours after a meal as a screening test. If there is sufficient insulin and good blood sugar control the blood sugar level should come back to normal 2 hours after a meal. If it is not, she has to undergo the diagnostic test.

There is lack of consensus about who to screen and the criteria for diagnosis. Urine should be checked for glucose at every antenatal clinic visit and if it is present further investigation is required. ie: the diagnostic test to diagnose gestational diabetes.

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Everybody has heard someone saying "I have 'blood sugar'". Everybody has sugar in their blood and nobody can survive without sugar in their blood indeed. Sugar levels in blood can give rise to problems when the sugar levels rise above the normal levels. Blood sugar is also called blood glucose. When the blood sugar levels go above normal, that condition is called Diabetes Mellitus.

Some women get diabetes only when they are pregnant. That entity is called 'Gestational diabetes' which is limited to the pregnancy. Gestational diabetes affects 2-3% of pregnant women. ie - 2-3 of every 100 women who are pregnant can get this.

This figure may be little high in this part of the world where majority of a meal is composed of carbohydrates or starch. If it is not properly controlled, it can lead to problems for the mother or her baby.

This article is not about pre-existing diabetes, which means women having diabetes before the onset of pregnancy. Pre-existing diabetics who are planning a pregnancy should convert themselves to have insulin injection if they are using oral medication for blood sugar control.

They should also take folic acid three months before the conception and continue at least up to twelfth week. Good blood sugar control around the time of conception should be their goal. Poor blood sugar control can give rise to miscarriages and anomalies (Eg - Heart defects) of the baby etc.

What is gestational diabetes?

It develops in women during pregnancy because of an increase in certain hormones, which can affect the blood sugar (glucose) levels. In other words, during pregnancy the placenta produces some hormones (chemicals) which block or act against the action of the hormone involved in blood sugar control (Insulin).

Therefore the body needs more insulin to control blood sugar. The mother's body is not always able to produce enough insulin to cope with this effect. If the body is not in a position to produce the required amount of insulin, the mother's blood sugar levels would rise. Raised blood sugar levels above a certain value is called diabetes.

When the blood sugar is sufficiently high, glucose can pass through to the kidneys and into the urine.

Gestational diabetes is more common in women who are overweight, older, have a family history of diabetes. Most women who suffer from the condition do not have any symptoms.

Symptoms of high blood sugar, such as increased thirst or increased need to pass urine, are common in pregnancy. Therefore it is difficult to pick up these patients during pregnancy as soon as they have it.

This condition in pregnancy It is often discovered after a routine urine test which is offered to all mothers universally as a screening test to pick up gestational diabetes.

This urine test checks for presence of sugar in the urine. The condition can occur at any time of pregnancy but usually begins after 24 to 28 weeks as the hormones that block the action of insulin starts to increase at this stage of the pregnancy and almost always disappears once the baby has been born.

Importance

Raised blood glucose levels in pregnancy are passed through the placenta to the developing baby causing an increased risk of complications during pregnancy, labour and delivery.

Causes

The cause is unknown. It is thought that the hormones produced during pregnancy may block the action of insulin. Gestational diabetes can happen if the mother's body can't produce enough extra insulin to counteract this blocking effect. It is an organ in the tummy called pancreas which produce the hormone insulin.

Tests

The diagnostic test is called 'oral glucose tolerance test' (OGTT) which involves giving a load of glucose (75 grams) to see how the body is coping with this load. The mother is kept fasting overnight and at first a blood sample is taken for a fasting blood sugar.

Then the glucose is given by mouth, and blood is taken hourly twice. If the system is working properly the blood glucose should return back to normal with in two hours.

Usually the diagnostic test is offered to following pregnant women.

1. Those who are at high risk of getting gestational diabetes (list given above). For these patients OGTT is offered between 24 to 28 weeks. Sometimes the test may have to be repeated at 32 weeks if it is normal at that period.

2. If there is sugar in urine at anytime of the pregnancy.

3. Those who are carrying large babies (Macrosomia) and when there is excess amount of water around baby (Polyhydramnios) which are complications of diabetic pregnancies.

4. If the blood sugar levels are high when a random blood sugar check is done. A random blood sugar is usually done two hours after a meal.

What are the type of results I can have following OGTT?

1. Normal - Most mothers will fall in to this category. The blood sugar levels are completely normal.

2. Gestational Diabetes - Depending on the fasting blood sugar or frequently with the two hour blood sugar value your doctor can arrive at a diagnosis of gestational diabetes.

3. Impaired glucose tolerance - Some consider this category as a separate entity whilst others consider this too as gestational diabetes, as there is lack of consensus in this area.

In this group the blood sugar levels are higher than the normal group but lower than the frank diabetic group.

Screening will detect 50% or more of all cases which means that up to half will not be screened or detected. Hence vigilance is required during antenatal care, especially if there is sugar in urine (glycosuria).

If the OGTT is performed at or before 24 weeks gestation, a negative result does not necessarily exclude future problems and if the results are borderline the test should be repeated between 32 and 34 weeks.

After diagnosis?

If Gestational Diabetes is diagnosed ,usually you will be admitted to hospital for control of blood sugar. Once your blood sugar levels are controlled, you will need to attend antenatal clinic, or admitted to the hospital, more frequently. You will attend a special clinic or combined antenatal clinic where you will be seen by both the diabetes team and the obstetric team.

Some times these patients will be seen in the same clinic where other moms are seen as special diabetic clinics for pregnant mothers are not available in many hospitals.

Advice will be given and an appointment will be arranged for you to see the dietician. You will need to monitor your blood sugar level regularly using a blood glucose meter, or from a local laboratory or hospital lab.

Treatment

In some cases a change in eating habits and a healthy diet will be all that is needed. This type of diet is called a 'diabetic diet' and you will be given an information leaflet on what to take and what not to etc.

It is important to reduce consumption of sugary foods like cakes, biscuits, soft drinks and tea etc. A diet that is low in fat is also desirable, the diet sheet will help you to achieve this. Gentle exercise may also prevent excessive weight gain in pregnancy, which will help to improve blood glucose control.

Usually if you are diagnosed as gestational diabetes the treatment is 'insulin' given as an injection. You will be put on a 'diabetic diet' too. But if you fall in to impaired glucose tolerance group, first you will be given a diabetic diet for about two days and then your blood sugars will be checked early in the morning (Fasting) and then two hours after each meal.

If these blood sugars are high you will be given insulin .

If your blood glucose does not return to normal with a healthy diet, it may be necessary to take insulin treatment for the remainder of your pregnancy. There is no fixed insulin regimen for everybody.

Therefore depending on how high the blood sugar levels are after each meal, you will be given insulin. Then again your blood sugars will be tested adjusting the dose of insulin to see if it is under control and this will be done frequently at the beginning until good control is achieved.

Once good control is achieved you will be taught how to inject your own insulin by yourself. There are new methods and preparations available which makes this an easy procedure (eg: Insulin pens) Once good control is achieved you will be discharged home from the hospital.

Then you will be asked to check your blood sugars two hours after each meal in a day (This is called a Blood sugar series and commonly known as BSS) once or twice a week throughout the pregnancy. As the pregnancy advances your insulin requirement can rise.

What are the effects of Gestational Diabetes on the Pregnancy.

Baby

Most women who have diabetes can have healthy babies, but they are at a higher risk of getting complications than a non-diabetic pregnancy.

Having high blood sugar levels can affect the baby's growth in the womb. This can cause the baby to grow larger (called macrosomia), which can sometimes make delivery difficult, but rarely it can also slow down the baby's growth especially if there is associated high blood pressure, and both of these can affect development.

If there is excess water around the baby (called polyhydramnios) which is seen commonly in diabetic pregnancies, it can lead to premature delivery giving rise to breathing problems of the baby.

Inside the womb the fetus produce extra amount of insulin to cope up with the high blood sugar levels which it receives through the umbilical cord. Shortly after birth, the baby may continue to make extra insulin even though high levels of blood sugar are no longer present.

This may cause the baby to have low blood sugar (hypoglycaemia) which can be harmful to the baby. Your baby will be observed for clinical signs of this and may have its blood glucose checked. If it is low it will be treated immediately by giving your baby a feed. Occasionally in a severe case, the baby might need a glucose drip.

It is more likely that your newborn baby will develop jaundice (yellow discolouration of skin). This usually fades over a few days, without the need for medical treatment.

Some babies may need phototherapy for a few days. Sometimes newborns, particularly if born early, can have breathing problems because their lungs have not fully matured. Excess blood sugar levels too can hamper the lung maturation. Extra oxygen may be needed at this time but only for a few days.

There is a slightly higher risk of sudden death inside the womb (intra uterine death-IUD), but if the glucose levels are reasonably controlled throughout pregnancy, this risk is lessened and is rare.

Will It Affect Labour?

If you are treated by diet alone then it will not affect your labour. If you need to take insulin your blood sugars will be checked regularly during labour and you may need a drip. To ensure the wellbeing of your baby it will be continually monitored. Most women with gestational diabetes, whose blood sugar levels stay within the safe range, deliver their babies without complications.

Labour carries little or no extra risk unless the baby is large. Providing all is well and blood sugars are controlled, mothers can expect a normal delivery at term. If spontaneous labour has not occurred by term the induction of labour will be arranged. The diabetes midwife will discuss all this with you at the 36-week antenatal check.

After Delivery?

After your baby is born your blood glucose level generally returns to normal. This happens basically due to expulsion of the placenta following delivery, which is the cause for onset of diabetes.

The drip will be stopped, your usual diet can resume, and the insulin will be discontinued. A glucose tolerance test will be arranged for you 6 to 8 weeks after your baby is born to ensure your blood glucose has returned to normal.

Breast feeding?

Yes, breast feeding is strongly encouraged and it also helps to bring down the blood sugar levels back to normal.

Diabetic after the baby?

If you have had diabetes during your pregnancy (Gestational Diabetes) there is a higher risk of you developing diabetes later in life. It is most common in women if you have other risk factors for diabetes like obesity, family members with diabetes etc.

It is always better to check your blood sugar levels at least once a year since diabetes can develop silently in later years. Passing more urine frequently, increased thirst, weight loss despite increased appetite and excessive tiredness are the main symptoms that you have to look out after pregnancy. To reduce the risk all should have a healthy lifestyle.

Diabetic in next pregnancy?

There is a higher risk of you getting diabetes in a subsequent pregnancy if you have had Gestational Diabetes in a previous pregnancy? Therefore it is important to tell your doctor or midwife as soon as you find that you are pregnant so that you will be offered an OGTT after 24 weeks.