There’s a phenomenon during pregnancy that causes “insulin resistance,” which means that although a pregnant woman makes insulin-it’s just that it’s lousier insulin. It simply doesn’t react to receptors at the cellular level as well, meaning it takes more to do what insulin is supposed to do-–bring sugar into the cells for energy. Being overweight makes this worse. In pregnancy, when the insulin made just can’t do the job anymore, we call this GDM (Gestational Diabetes Mellitus). Since the insulin isn’t as powerful, a diet low in sugar and carbohydrates will mean less sugar in the system; less sugar in the system means less left over from the faulty insulin chemistry. This is what is meant by diet-controlled gestational diabetes and actually works fairly well with this condition.
Because diet does work well, very few women need insulin injections with GDM. Sometimes, as many as 1 out of 10 – 20 pregnancies will have GDM. It used to be a sneaky disease until we started screening all pregnancies with the O’Sullivan test (a 1-hour blood glucose determination after a sugar drink). Out of those with an abnormal test, a full 3-hour glucose tolerance test (a fasting, followed by 3 subsequent sugar determinations after a sugar drink) will then pick out the real GDM patients. GDM can have the same complication as “regular” diabetes – large babies – so it is important to manage it aggressively.
And then there are the “real” diabetics.
Diabetes Mellitus This isn’t making insulin that lackluster. This is actually not making enough insulin at all. When there isn’t enough insulin to bring sugar from the blood stream (your blood stream is what you eat) into the tissue, it builds up in the blood stream, gunking up the works. This leads to damage of the blood supply to one’s organs, resulting in kidney damage, eye damage, etc.
Women who are diabetic when they conceive are at twice the risk for abnormal fetuses, even when their blood sugars are well controlled. But even with this doubled risk, the chances of having a baby with congenital abnormalities is only 4 to 5 out of a hundred.
But diabetic women who have blood sugars that aren’t well controlled have a staggering increase in their risk-–by about ten times what their normal risk would be for a well-controlled diabetic state. So the real deal-breaker here is good control before conception. Luckily, there’s a test that can tell how well the diabetes has been controlled. It is called an HbA1c (Hemoglobin A1C) and measures how much sugar is “stuck” to a certain hemoglobin molecule. The beauty of this relationship between hemoglobin and glucose is that it’s a firm interaction-–meaning that it reflects how well the diabetes has been in control for a long time, usually months.
So a normal HbA1c in the first trimester will be a very reassuring test for a pregnant diabetic patient. And the risk of congenital abnormalities and miscarriage is directly related to how abnormally high the HbA1c is. This makes it, besides the serum glucose measurement, the most important prenatal (and preconception!) test in diabetic pregnancy.
But even with good control preconception and during the first trimester, the two natural enemies, pregnancy and diabetes, begin to fight it out. The very thing that can cause that normal variation known as GDM can make insulin-dependent diabetes harder to manage, too, by driving up the insulin needs. This means that no “set” dosage of insulin can be established with expectations of the pregnancy sugar control to be on automatic pilot. It doesn’t work that way, and pregnancy + diabetes is usually a continuing medical challenge always at red alert.
Large babies make for more difficult vaginal deliveries. Besides the risk of cephalopelvic dysproportion (baby’s to big to fit out), and shoulder dystocia (head delivers but shoulders get stuck), there is also increased risk of placental abruption (premature separation). Since the C-section rate is higher in diabetic patients for all of the above reasons, it’s important to know that Cesarean delivery is not the perfect answer to a pregnant diabetic’s problems. Diabetic women don’t heal well after surgery and their chances of infection are much greater.
In spite of all of these concerns, a woman whose sugars are well controlled can stack the deck in her favor, especially if she is evaluated preconception. But diabetes is a definite problem in pregnancy that requires diligence on the part of the obstetrician and strict compliance on the part of the patient.
What is Gestational Diabetes and What Causes It?
Diabetes (actual name is diabetes mellitus) of any kind is a disorder that prevents the body from using food properly. Normally, the body gets its major source of energy from glucose, a simple sugar that comes from foods high in simple carbohydrates (e.g., table sugar or other sweeteners such as honey, molasses, jams and jellies, soft drinks, and cookies), or from the breakdown of complex carbohydrates such as starches (e.g., bread, potatoes, and pasta). After sugars and starches are digested in the stomach, they enter the blood stream in the form of glucose. The glucose in the blood stream becomes a potential source of energy for the entire body, similar to the way in which gasoline in a service station pump is a potential source of energy for your car. But, just as someone must pump the gas into the car, the body requires some assistance to get glucose from the blood stream to the muscles and other tissues of the body. In the body, that assistance comes from a hormone called insulin. Insulin is manufactured by the pancreas, a gland that lies behind the stomach. Without insulin, glucose cannot get into the cells of the body where it is used as fuel. Instead, glucose accumulates in the blood to high levels and is excreted or “spilled” into the urine through the kidneys.
When the pancreas of a child or young adult produces little or no insulin we call this condition juvenile-onset diabetes or Type I diabetes (insulin-dependent). This is not the type of diabetes you have. Unlike women with Type I diabetes, women with gestational diabetes have plenty of insulin. In fact, they usually have more insulin in their blood than women who are not pregnant. However, the effect of their insulin is partially blocked by a variety of other hormones made in the placenta, a condition often called insulin resistance.
The placenta performs the task of supplying the growing fetus with nutrients and water from the mother’s circulation. It also produces a variety of hormones vital to the preservation of the pregnancy. Ironically, several of these hormones such as estrogen, cortisol, and human placental lactogen (HPL) have a blocking effect on insulin, a “contra-insulin” effect. This contra-insulin effect usually begins about midway (20 to 24 weeks) through pregnancy. The larger the placenta grows, the more these hormones are produced, and the greater the insulin resistance becomes. In most women the pancreas is able to make additional insulin to overcome the insulin resistance. When the pancreas makes all the insulin it can and there still isn’t enough to overcome the effect of the placenta’s hormones, gestational diabetes results. If we could somehow remove all the placenta’s hormones from the mother’s blood, the condition would be remedied. This, in fact, usually happens following delivery.
What can be done to reduce problems associated with gestational diabetes?
In addition to your obstetrician, there are other health professionals who specialize in the management of diabetes during pregnancy including internists or diabetologists, registered dietitians, qualified nutritionists, and diabetes educators. Your doctor may recommend that you see one or more of these specialists during your pregnancy. In addition, a neonatologist (a doctor who specializes in the care of newborn infants) should also be called in to manage any complications the baby might develop after delivery.
One of the essential components in the care of a woman with gestational diabetes is a diet specifically tailored to provide adequate nutrition to meet the needs of the mother and the growing fetus. At the same time the diet has to be planned in such a way as to keep blood glucose levels in the normal range (60 to 120 mg/dl). Specific details about diet during pregnancy are discussed later.
An obstetrician, diabetes educator, or other health care practitioner can teach you how to measure your own blood glucose levels at home to see if levels remain in an acceptable range on the prescribed diet. The ability of patients to determine their own blood sugar levels with easy-to-use equipment represents a major milestone in the management of diabetes, especially during pregnancy. The technique called “self blood glucose monitoring” (discussed in detail later) allows you to check your blood sugar levels at home or at work without costly and time-consuming visits to your doctor. The values of your blood sugar levels also determine if you need to begin insulin therapy sometime during pregnancy. Short of frequent trips to a laboratory, this is the only way to see if blood glucose levels remain under good control.
What is self blood glucose monitoring?
Once you are diagnosed as having gestational diabetes, you and your health care providers will want to know more about your day-to-day blood sugar levels. It is important to know how your exercise habits and eating patterns affect your blood sugars. Also, as your pregnancy progresses, the placenta will release more of the hormones that work against insulin. Testing your blood sugar level at important times during the day will help determine if proper diet and weight gain have kept blood sugar levels normal or if extra insulin is needed to help keep the fetus protected.
Self blood glucose monitoring is done by a special device to obtain a drop of your blood and test it for your blood sugar level. Your doctor or other health care provider will explain the procedure to you. Make sure that you are shown how to do the testing before attempting it on your own. Some items you may use to monitor your blood sugar levels are:
- Lancet – a disposable, sharp needle-like sticker for pricking the finger to obtain a drop of blood.
- Lancet device – a spring-loaded finger sticking device.
- Test strip – a chemically treated strip to which a drop of blood is applied.
- Color chart – a chart used to compare against the color on the test strip for blood sugar level.
Your health care provider can advise you where to obtain the self-monitoring equipment in your area. You may want to inquire if any places rent or loan glucose meters, since it is likely you won’t be needing it after your baby is born. Glucose meter – a device which “reads” the test strip and gives you a digital number value.