Gestational Diabetes (1)
Definition
Why Screen for It and What Complications May Arise?
Who, When, and How?
Why is it screened at 24 weeks and not earlier?

Diabete general1 english

Dr. Claude Allouche, Gynecologist,
Ahuza Clinic, Raanana, Israel
058 726 02 64

Definition

Gestational diabetes is defined by the World Health Organization (WHO) as a glucose tolerance disorder leading to hyperglycemia, which appears or is diagnosed for the first time during pregnancy. In Hebrew, it is called "sakeret herayon" (סכרת הריון).

Two Categories of Gestational Diabetes

1. Undiagnosed Diabetes Discovered During Pregnancy

Description: This is typically type 2 diabetes that existed before pregnancy but was discovered through routine testing in early pregnancy.
Diagnosis: Fasting blood glucose > 1.26 g/L before or in the first trimester.
Course: This diabetes persists after delivery.

2. True Gestational Diabetes

Description: This diabetes develops only during pregnancy, often due to the body's inability to produce enough insulin to manage increased blood glucose.
Mechanism: During pregnancy, the placenta produces hormones that make the body less responsive to insulin (insulin resistance), a phenomenon that becomes more pronounced after 24 weeks of gestation.
Diagnosis: Done via an oral glucose tolerance test (OGTT) usually between 24 and 28 weeks.
Prevalence: Estimated to affect 2% to 6% of pregnant women, with higher rates in certain populations:

  • Overweight or Obesity: 19.1% prevalence in obese women and 11.1% in overweight women (BMI ≥ 25 kg/m²).
  • Advanced Age: 14% prevalence in women over 35 years old.
  • Family History: Type 2 diabetes in a first-degree relative.
  • Personal History: Previous gestational diabetes or macrosomia (baby weighing over 4000 g at birth).

Why Screen for It and What Complications May Arise?

Why Screen for It? GESTATIONAL DIABETES (1): WHAT IS IT? DEFINITION

  • Frequency: Between 3% and 6% of pregnant women will develop gestational diabetes.
  • Complications: If not well-controlled, gestational diabetes can lead to complications for both mother and baby.

A] Complications for the Baby:

The fetus receives nutrients through the mother's blood via the placenta. In response to excess glucose, the fetus produces insulin that promotes fat storage, potentially leading to excessive growth, a condition known as macrosomia. The baby might be large but fragile, with higher risks of:

  • Shoulder dystocia during vaginal delivery: Studies have shown that at the same birth weight, the risk is higher for babies of diabetic mothers compared to non-diabetic mothers. This complication can lead to brachial plexus paralysis, potentially causing lifelong disability.
  • Hypoglycemia: At birth, babies, especially those with macrosomia or born to mothers with poorly controlled diabetes, are at risk of hypoglycemia.
    In cases of gestational diabetes, the risk of neonatal hypoglycemia is 2.6 times higher when the birth weight exceeds 4000 g.
  • Hypocalcemia: The frequency of neonatal hypocalcemia in maternal diabetes cases is debated, with rates up to 30% in poorly controlled cases.
  • Jaundice: Hyperbilirubinemia is usually not severe if managed properly.
  • Respiratory distress: Babies of diabetic mothers are more at risk for neonatal respiratory distress due to premature birth, surfactant production issues, or cesarean delivery.
  • Congenital anomalies: If diabetes is present early in pregnancy, there is an increased risk of fetal malformations, such as heart defects, caudal regression syndrome, neural tube defects, and skeletal abnormalities.
  • Stillbirth: Undiagnosed or poorly controlled diabetes increases the risk of fetal death in utero.

B] Complications for the Mother:

Gestational diabetes raises the risk of:

  • Preeclampsia: High blood pressure during pregnancy, with swelling and protein in the urine.
  • Urinary infections during pregnancy.
  • Cesarean delivery or perineal tears due to macrosomia during vaginal delivery.

Clinical studies show that women with gestational diabetes:

  • Are more likely to experience it again in future pregnancies.
  • Have at least a 50% chance of developing type 2 diabetes later in life.

Screening for Gestational Diabetes: Who, When, and How?

WHEN?

Screening for gestational diabetes is done by:

  • A fasting blood glucose test in the first trimester.
  • An oral glucose tolerance test between 24 and 28 weeks of gestation, called "hamasat soukar" (המסת סוכר) in Hebrew.

Screening can also be done in the third trimester for women with risk factors who haven’t had earlier screening.
Fetal macrosomia or polyhydramnios (excess amniotic fluid) should also prompt screening.

WHO?

  • In Israel, screening is recommended for all pregnant women.
  • In France, screening is only recommended for at-risk patients.

HOW? Diagnostic Criteria:

1/ In the first trimester:

  • A fasting blood glucose > 0.92 g/L indicates gestational diabetes.
  • Fasting glucose ≥ 1.26 g/L indicates type 2 diabetes.

2/ Between 24 and 28 weeks:
The period during which glucose tolerance worsens during pregnancy, using two methods:
A] WHO's G75 test (used in France):
B] O'Sullivan's G50 test (used in Israel).

Why is it Screened at 24 Weeks and Not Before?

The body’s glucose regulation evolves throughout pregnancy. During the second half, the placenta produces hormones that cause insulin resistance, which is more noticeable after 24 weeks of gestation. Screening earlier might result in falsely reassuring results.