Diabetes and Pregnancy

What is diabetes?

Diabetes is a condition in which the body can't produce enough insulin, or it can't use it properly. Insulin is the hormone that allows glucose (sugar) to enter the cells to be used as fuel. When glucose cannot enter the cells, it builds up in the blood. This is called hyperglycemia or high blood sugar. Damage from diabetes comes from the effects of hyperglycemia on other organ systems including the eyes, kidneys, heart, blood vessels, and nerves. In early pregnancy, hyperglycemia can result in birth defects.

What are the different types of diabetes?

There are 3 basic types of diabetes including:

  • Type 1 diabetes. Also called insulin-dependent diabetes mellitus (IDDM), type 1 diabetes is an autoimmune disorder in which the body's immune system destroys, or attempts to destroy, the cells in the pancreas that produce insulin. Type 1 diabetes usually develops in children or young adults, but can start at any age.

  • Type 2 diabetes. A metabolic disorder resulting from the body's inability to make enough, or properly use, insulin. It used to be called noninsulin-dependent diabetes mellitus (NIDDM).

  • Gestational diabetes. A condition in which the blood glucose level is elevated and other diabetic symptoms appear during pregnancy in a woman who has not previously been diagnosed with diabetes.

Diabetes is a serious disease, which, if not controlled, can be life-threatening. It is often associated with long-term complications that can affect every system and part of the body. Diabetes can contribute to eye disorders and blindness, heart disease, stroke, kidney failure, amputation, and nerve damage.

What happens with diabetes and pregnancy?

During pregnancy, the placenta supplies a growing fetus with nutrients and water. The placenta also makes a variety of hormones to maintain the pregnancy. In early pregnancy, hormones can cause increased insulin secretion and decreased glucose produced by the liver, which can lead to hypoglycemia (low blood glucose levels). In later pregnancy, some of these hormones (estrogen, cortisol, and human placental lactogen) can have a blocking effect on insulin, a condition called insulin resistance.

As the placenta grows, more of these hormones are produced, and insulin resistance becomes greater. Normally, the pancreas is able to make additional insulin to overcome insulin resistance, but when the production of insulin is not enough to overcome the effect of the placental hormones, gestational diabetes results or there may be worsening of pregestational diabetes.

Why is diabetes a concern in pregnancy?

Diabetes in pregnancy can have serious consequences for the mother and the growing fetus. The severity of problems often depends on the degree of the mother's diabetic disease, especially if she has vascular (blood vessel) complications and poor blood glucose control. Diabetes that occurs in pregnancy is often listed according to White's classification:

  • Gestational diabetes. When a mother who does not have diabetes develops a resistance to insulin because of the hormones of pregnancy.

    • Class A1, which can be controlled by changes in diet

    • Class A2, which requires insulin or oral hypoglycemic medication for control

  • Pre-gestational diabetes. Women who already have insulin-dependent diabetes and become pregnant.

    • Class B - diabetes developed after age 20, have had the disease less than 10 years, no vascular complications.

    • Class C - diabetes developed between age 10 and 19 or have had the disease for 10-19 years, no vascular complications.

    • Class D - diabetes developed before age 10, have had the disease more than 20 years, vascular complications are present.

    • Class F - diabetic women with kidney disease called nephropathy.

    • Class R - diabetic women with retinopathy (retinal damage).

    • Class T - diabetic women who have undergone kidney transplant.

    • Class H - diabetic women with coronary artery or other heart disease.

It is very important for a mother to closely manage her diabetes during pregnancy. Generally, the poorer the control of blood glucose and the more severe the disease and complications, the greater the risks for the pregnancy.

Maternal complications of diabetes on a pregnancy

Complications for the mother depend on the degree of insulin need, the severity of complications associated with diabetes, and control of blood glucose.

Most complications occur in women with pre-gestational diabetes and are more likely when there is poor control of blood glucose. Women may require more frequent insulin injections. They may have very low blood glucose levels, which can be life threatening if untreated, or they may have ketoacidosis, a condition that results from high levels of blood glucose. Ketoacidosis may also be life threatening if untreated. It is not clear whether pregnancy worsens diabetic related blood vessel damage and retinal changes, or if it causes changes in kidney function.

Complications for fetus and baby

Infants of mothers with diabetes are at greater risk for several problems, especially if blood glucose levels are not carefully controlled, including the following:

  • Birth defects. Birth defects are more likely in infants of diabetic mothers, especially insulin-dependent women who may have two to six times greater the risk of major birth defects. Some birth defects are serious enough to cause fetal death. Birth defects usually originate sometime during the first trimester of pregnancy. They are more likely in women with pre-gestational diabetes, who may have changes in blood glucose during that time. Overall, major birth defects may occur in about 5% to 10% of infants born to insulin-dependent women. Major birth defects that may occur in infants of diabetic mothers include the following:

    • Heart and connecting blood vessels

    • Brain and spine abnormalities

    • Urinary and kidney

    • Digestive tract

  • Stillbirth (fetal death). Stillbirth is more likely in pregnant women with diabetes. The fetus may grow slowly in the uterus due to poor circulation or other conditions, such as high blood pressure or microvascular disease, which can complicate diabetic pregnancy. The exact reason stillbirths occur with diabetes is unknown. The risk of stillbirth increases in women with poor blood glucose control and with blood vessel changes.

  • Macrosomia. Macrosomia refers to a baby that is considerably larger than normal. All of the nutrients the fetus receives come directly from the mother's blood. If the maternal blood has too much glucose, the pancreas of the fetus senses the high glucose levels and produces more insulin in an attempt to use this glucose. The fetus converts the extra glucose to fat. Even when the mother has gestational diabetes, the fetus is able to produce all the insulin it needs. The combination of high blood glucose levels from the mother and high insulin levels in the fetus results in large deposits of fat that causes the fetus to grow excessively large.

  • Birth injury. Birth injury may occur due to the baby's large size and difficulty being born.

  • Hypoglycemia. Hypoglycemia is low levels of blood glucose in the baby immediately after delivery. This problem occurs if the mother's blood glucose levels have been consistently high causing the fetus to have a high level of insulin in its circulation. After delivery, the baby continues to have a high insulin level, but no longer has the high level of glucose from the mother, resulting in the newborn's blood glucose level becoming very low. The baby's blood glucose level is checked after birth, and if the level is too low, it may be necessary to give the baby glucose intravenously.

  • Respiratory distress (difficulty breathing). Too much insulin or too much glucose in a baby's system may delay lung maturation and cause respiratory difficulties in babies. This is more likely in babies born before 37 weeks of pregnancy.

How is diabetes diagnosed?

Women with diabetes before pregnancy have already been diagnosed. Depending on the severity of their disease, they may need continued care by their health care provider along with their obstetrician.

Nearly all nondiabetic pregnant women are screened for gestational diabetes between 24 and 28 weeks of pregnancy. In addition to a complete medical history and physical exam, a glucose screening test is given, which involves drinking a special glucose drink followed by measurement of glucose levels after a 1-hour interval.

If this test shows an increased blood glucose level, a 3-hour glucose tolerance test will be done.

If results of the second test are in the abnormal range, gestational diabetes is diagnosed.

Treatment for diabetes

Your health care provider will figure out the best treatment for you based on:

  • How old you are

  • Your overall health and medical history

  • How sick you are

  • How well you can handle specific medications, procedures, or therapies

  • How long the condition is expected to last

  • Your opinion or preference

Treatment for diabetes focuses on keeping blood glucose levels in the normal range. Treatment may include:

  • Special diet with controlled amounts of carbohydrate

  • Exercise

  • Blood glucose monitoring

  • Insulin injections

  • Certain oral hypoglycemics

Managing diabetes during the pregnancy

Special fetal testing and monitoring may be needed for pregnant diabetics, especially those who are taking insulin (because of the increased risks for stillbirth). These tests can include the following:

  • Fetal movement counting. Counting the number of movements or kicks in a certain period of time, and watching for a change in activity.

  • Ultrasound. A diagnostic imaging technique which uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs. Ultrasounds are used to view internal organs as they function, and to assess blood flow through various vessels.

  • Nonstress testing. A measurement of the fetal heart rate in response to the fetus' movements.

  • Biophysical profile. A test that uses the nonstress test and ultrasound to examine fetal movements, heart rate, and amniotic fluid amounts.

  • Doppler flow studies. A type of ultrasound which uses sound waves to measure blood flow.

Infants of diabetic mothers may be delivered vaginally or by cesarean, depending on the estimated fetal weight and the mother's health.  An amniocentesis may be done in the last few weeks of pregnancy to check the amniotic fluid for fetal lung maturity, as the lungs mature more slowly in babies whose mothers have diabetes. If the lungs are mature, some mothers may have labor induced or, depending on the estimated fetal weight,  a cesarean delivery.