Gestational Diabetes: Signs, Causes, and Risk Factors

Gestational diabetes usually does not manifest in any obvious symptoms. However, blurred vision, fatigue, frequent infections, increased urination and thirst, and nausea may be signs and symptoms of gestational diabetes. Gestational diabetes can only be diagnosed through routine prenatal testing and screening.

During pregnancy, the body produces a larger amount of certain hormones to help maintain a healthy pregnancy and provide nutrients to the baby. This increase in hormones can interfere with insulin, a substance which takes glucose (sugar) out of the bloodstream and uses it for energy. This causes higher blood sugar levels, which is normal in pregnancy because the extra glucose is needed to support the baby. But when the amount of insulin produced is less than what is needed to handle blood sugar levels, it can lead to high levels of glucose in the bloodstream (this is also known as hyperglycemia), and gestational diabetes can occur.

Risk for gestational diabetes may increase if the patient has any of the following conditions:

• A previous diagnosis of gestational diabetes or prediabetes, poor impaired glucose tolerance, or impaired fasting glycemia
• A family history of type 2 diabetes
• Maternal obesity
• Advanced maternal age (over 35)
• Previously birthed a baby that weighed more than 9 pounds
• High blood pressure and preeclampsia
• Too much amniotic fluid (polyhydramnios)
• Significant weight gain before or during the first 18-24 weeks of pregnancy
• Medical conditions associated with risk for diabetes, such as polycystic ovary syndrome (PCOS)

The American Congress of Obstetrics and Gynecologists (ACOG) recommends that all pregnant patients receive an oral glucose tolerance test between the 24th and 28th week of pregnancy. People who have risk factors for gestational diabetes may have this test earlier in the pregnancy, typically around the 18th week.  Patients who develop pregnancy-related diabetes should also be re-tested 6-12 weeks after delivery.

To test for gestational diabetes, the patient will drink a syrupy solution and their blood will be tested to check glucose level an hour later. A follow-up test is then given where the patient fasts overnight and then has their blood sugar tested the next morning. After the second test, they will drink a solution that has an even higher level of glucose than the solution given during the initial test. The patient’s blood glucose level will then be checked every hour for a period of three hours. If at least two of the blood glucose readings are higher than normal, the patient will be diagnosed with gestational diabetes.

With gestational diabetes, frequent check-ups by the physician are essential, especially during the last three months of pregnancy, and especially if the patient has other factors that make them a high-risk pregnancy.

Once a patient is diagnosed with gestational diabetes, the physician will have them monitor their diabetes by testing their glucose levels at home. The most common way is to draw a drop of blood from a finger using a device that will give a glucose reading. The goals of treatment are to keep blood glucose levels within normal limits during the pregnancy and to make sure the growing baby is healthy.

In addition to close monitoring, it is recommended that mothers with gestational diabetes be treated with dietary counseling, oral hypoglycemic medications, or insulin.

Currently, the American College of Obstetricians and Gynecologists (ACOG) and the American Diabetes Association recommend screening all pregnant patients for gestational diabetes.

Due to the multiple, serious complications that can arise from gestational diabetes , rigorous testing and monitoring is important. According to a 2008 study that spanned multiple countries, the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) trial, even subtle defects in maternal glucose metabolism during pregnancy may lead to health problems for mother and baby (2).

Gestational diabetes places mothers in the high-risk pregnancy category, as it poses an increased risk for complications during pregnancy, labor, and delivery. With proper monitoring and care, however, many of the risks associated with gestational diabetes can be mitigated, resulting in a healthy baby.

Monitoring may include non-stress testing for fetal well-being, ultrasounds for fetal well-being, fetal size and amniotic fluid levels and Doppler flow studies.

In many cases, it is safest for babies of mothers with gestational diabetes to be delivered in a scheduled delivery prior to 40 weeks . If a mother’s diabetes is poorly controlled, delivery is recommended as early as week 36. Although premature birth does have associated risks, in the case of diabetes, the benefits of early delivery outweigh the risks, especially with proper postnatal care.

The high blood sugar levels associated with gestational diabetes are often passed on to the baby through the placenta. This extra amount of energy is put towards growth and can result in a baby being too large (macrosomic), which increases the baby’s risk of a traumatic birth, like getting stuck or injured in the birth canal. Babies with macrosomia are most safely delivered via C-section. If macrosomia goes undetected or cesarean section is not performed, this may result in a prolonged or arrested labor, traumatic injury to the baby, or HIE.

Once babies are born, they begin to produce their own glucose and energy stores. While in utero, babies produce larger quantities of insulin to process the existing larger supply of blood sugar from the placenta.

When babies from a gestational diabetes pregnancy are born, the amount of insulin they produce does not drop as quickly as their glucose supply does, since they are used to a larger supply of glucose in utero. If they don’t take in enough energy as newborns, their blood sugar can drop dangerously low. This is extremely problematic because blood sugar is the sole energy source for the brain. If low blood sugar (hypoglycemia) continues, brain cells begin to die, which can cause seizures and permanent brain damage. Generally, after birth, it’s very important to monitor the baby’s blood sugar – especially if their mother had diabetes – in order to prevent it from dipping too low.

Hypoxic-ischemic encephalopathy (HIE) is a brain injury caused by a lack of blood and oxygen flow to the brain. This can happen due to complications associated with diabetes, such as prolonged labor or traumatic delivery due to macrosomia or placental insufficiency. Medical practitioners are trained to monitor and recognize the specific events and conditions that could potentially cause injury – and should be trained to avoid injury and provide care that is up to the ‘standard of care.’ If they do not provide proper care, the baby may suffer HIE, which can result in cerebral palsy.

Neonatal seizures are one sign that a baby has neurological abnormalities. Seizures are abnormal electrical discharges in the brain and are common in neonatal hypoglycemia. Neonatal hypoglycemia can damage brain cells, which in turn can cause seizures. It is very important that medical professionals bring seizures under control because continuing seizures can make underlying brain damage worse.

Mothers with gestational diabetes can sometimes have poor placental perfusion or placental insufficiency, which affects the flow of blood to the baby through the umbilical cord. This can cause the baby to be deprived of oxygen in the uterus (chronic intrauterine hypoxia). These conditions can cause the baby to produce too many red blood cells. Babies’ livers break down these red blood cells, releasing a substance called bilirubin into the blood. When too much bilirubin is released (hyperbilirubinemia), the baby’s skin and eyes can turn yellowish. This condition is called jaundice.

It is common practice to induce labor prior to 40 weeks for women with gestational diabetes as a strategy to reduce complications, especially those related to macrosomia. Labor induction is often planned at 38 ½ to 39 weeks’ gestation and can occur when the baby’s lungs are mature, antepartum tests are normal, diabetes is under control, and the mother doesn’t have vascular disease.

ACOG recommends consideration of C-section delivery in diabetic women when estimated fetal weight exceeds 4500 grams, though some researchers recommend C-section delivery between 4000 and 4500 grams, after evaluating obstetrical history and clinical measurements of the pelvis. Physicians should be alerted to the possibility of cephalopelvic disproportion if dilation or descent stops during labor, and the baby’s estimated weight exceeds 4000 grams. These researchers also suggest consideration of C-section delivery in diabetic women who demonstrate significant protracted labor and failure of descent – in other words, they are slower to dilate and the baby does not descend down the birth canal.