Overview of Type 2 Diabetes and Pregnancy.
In order to understand Type 2 Diabetes, it is necessary to understand how insulin works. The hormone, insulin, which comes from the pancreas, controls blood sugar. The role of insulin is to get the sugar into the cells.
Type 2 diabetes can be defined by two main problems: first, the pancreas is not making enough insulin; and secondly, the insulin that is made is not working properly because of a resistance to insulin. Since pregnancy makes insulin resistance worse, Type 2 diabetes tends to get worse during pregnancy. If you are currently managing with an approved diet or if you take tablets, in all likelihood you will need insulin during the pregnancy. If you are on insulin, then it is likely that you will need much more insulin to keep the blood sugar controlled during pregnancy. Since Type 2 diabetes is becoming much more common at a younger age, more women are being seen in pregnancy clinics with Type 2 diabetes.
Issues for the mother
Pregnancy has an impact not only on glucose control but also blood pressure, blood volume hemodynamics and the complications of diabetes. It should be appreciated that Type 2 diabetes and pregnancy is more recently becoming much more an issue so there are not many studies in women with Type 2 diabetes and pregnancy. Thus we have extrapolated from what we know about Type 1 diabetes and pregnancy. There are four major diabetes complications that have to be considered:
Eye damage
The risk that the eyes may show some progression ranges from 10 to 50% with this risk being proportional to the status of the eyes at the start of the pregnancy. If there is minimal or no damage present then there is about a 10% chance of some changes occurring, if there is a lot of damage present then the risk of progression is about 50%. Hence the need for a formal eye exam ideally pre or early in the pregnancy as how one sees tells little about what is going on in the back of the eye where diabetes causes problems.
Kidney damage
When kidney damage occurs it is typically in the form of a leakage of protein in the urine and a rise in blood pressure. Like with the eyes the risk of change is proportional to the starting point. If there is no leakage of protein at the start then the risk of protein leaking and a rise in blood pressure is 10 – 20%. If there is protein in the urine at the start of the pregnancy then the risk of this becoming significantly worse is 40 – 60%. This worsening nearly always settles after the baby is born, however, if the problems at the start are more severe, leakage of protein and a raised creatinine then the progression of the kidney damage may not revert back to the starting level post partum.
Nerve damage
Diabetic nerve damage tends to remain unchanged during pregnancy. Diabetic women who become pregnant are more prone to carpal tunnel syndrome (pain down the wrist and into the hand, usually worse in the morning). This may need a splint if severe and typically goes away after delivery.
Blood vessels
Although there is increased blood volume during pregnancy, circulation problems tend to hold stable during pregnancy. Should a heart attack occur the outcome tends to be more ominous if pregnant. If the woman is prepregnant and has a long history of diabetes it may be worth having a cardiac stress test to be sure all is well. This may be particularly important if there is some kidney disease, high cholesterol or a family history of heart attacks.
Issues for the baby
Having diabetes during the pregnancy has important implications for the baby. These can be considered to relate to the first 6 – 8 weeks of pregnancy and then the remainder of the pregnancy.
First 6 – 8 weeks
Congenital Malformations
If the glucose is not well controlled during the first 6 – 8 weeks after conception there is an increased chance that a malformation may occur. Although sometimes minor, they may be serious and include heart, kidney or spine defects. Controlling the blood sugar eliminates this increased risk. The best measure of sugar control is the A1c, the lower the better but is should be at least under 7.0% (in laboratories with an A1c upper limit of normal of 6.1%) prior to conception. Of all the risks for the baby this is by far the most serious and this increased risk can be eliminated by controlling the glucose before one gets pregnant.
Remainder of pregnancy
Big babies
When the sugar is high during the pregnancy it can freely cross into the baby and it is as if the baby converts the sugar into fat. These bigger babies are more difficult for both the mother and infant at time of delivery. It is important to remember that there are other causes of big babies and sugar is only one of the reasons a baby may be large.
Hypoglycemia
If the baby is repeatedly exposed to high sugars from the mother, the baby’s own pancreas starts to make extra insulin so after birth the baby may have some low blood sugars, hypoglycemia.
Jaundice and Respiratory distress
Although these babies may be born large they act more as if premature and thus are more prone to jaundice and rarely respiratory problems.
What happens to blood sugars/medications
The oral hypoglycemic medicines are not formally approved for use in pregnancy but most people working in the area feel they are safe. Since the amount of insulin the body needs will increase during a pregnancy most centers suggest switching to insulin pre pregnancy so one is not trying to learn about insulin during the pregnancy. Some physicians believe that Metformin helps to achieve ovualation in women with polycystic ovarian syndrome and so will use Metformin. There are some studies suggesting that Metformin may reduce the rate of miscarriage and it may be worth continuing in the first trimester especially if there is a history of miscarriages.
During the first 14 weeks the amount of insulin needed if anything decreases and so one needs to be careful of hypoglycemia. This is likely in part related to morning sickness and some of the hormone changes. From 14 weeks onwards, hormones from the placenta begin to rise and these block how insulin works. Thus the amount of insulin needed to control the blood sugar increases so that by the end of pregnancy the mom with Type 2 diabetes will usually be taking about one and a half to two fold her prepregnancy insulin dose.
Some women are on drugs to control cholesterol called statins. These are not considered safe in pregnancy and usually should be stopped once trying to get pregnant. Blood pressure drugs belonging to the ACE (angiotensin converting enzyme) inhibitor class or ARB’s (angiotensin receptor blockers) are also not considered safe for the baby and should be stopped. There are other blood pressure drugs that can be safely used if needed. Finally all women planning a pregnancy should be on prenatal vitamins with 1 mg of folic acid.