Handbook of Genetic Counseling/Diabetes in Pregnancy

Diabetes in Pregnancy

Overview of DiabetesEdit

  • Disorder in which body doesn't produce enough insulin or doesn't use insulin properly
    • Insulin is hormone made by pancreas
    • Insulin lets body turn blood sugar into energy or store it as fat
  • If diabetes is untreated, high levels of sugar accumulate in blood
    • Can damage organs
      • Blood vessels
      • Nerves
      • Eyes
      • Kidneys
    • Daily insulin injections may help prevent these complications
  • Three types of diabetes
    • Insulin-dependent diabetes mellitus (IDDM)
      • Type I or juvenile diabetes
      • B cells don't produce insulin
      • Classic presentation
        • Weight loss
        • Increased appetite
        • Increased thirst
        • Excessive urination
        • Severe cases can cause ketoacidosis
    • Non-insulin dependent diabetes mellitus (NIDDM)
      • Type II diabetes
      • Classically seen in adults who are overweight
      • Insulin is present but insulin receptors unresponsive
    • Gestational diabetes
      • Caused by hormones or other factors that interfere with bodies ability to use insulin during pregnancy
      • Many women have no symptoms
      • Risk factors to develop gestational diabetes:
        • Over age 30
        • Obesity
        • Family history of diabetes
        • Personal history of gestational diabetes - 50% recurrence
        • Previous baby over 9 ½ pounds
        • Previous stillbirth
      • Occurs most frequently in African-Americans, Hispanic/Latino Americans, Pacific Islanders, and American Indians
      • Usually develops during second half of pregnancy
      • Most women can control insulin levels with diet and exercise
      • Women with gestational diabetes have 50% chance of developing diabetes after pregnancy

Diabetes in PregnancyEdit

  • Incidence
    • About 1 in 100 women of childbearing age have diabetes before pregnancy
    • About 3-5% of women develop gestational diabetes
  • Risks to fetus
    • In general, the more severe the diabetes, the more severe the outcome
    • Poorly controlled diabetes (all types)
      • Risk for congenital malformations related to severity of diabetes
        • Women with IDDM and uncontrolled NIDDM have 2-3 times incidence of congenital anomalies (6-8%)
        • Women with NIDDM have median risk
        • Women with gestational diabetes at small increased risk
      • Increased risk for macrosomia (25-45%)
        • Baby 10 pounds or more at birth
        • Due to extra sugar in mother's blood that crosses the placenta to fetus
        • Fat tends to accumulate around shoulders and trunk
        • Makes babies difficult to deliver vaginally
        • Can lead to increase in shoulder dystocia, clavicular fracture, and Erb's Palsy
      • Increased risk for pregnancy complications
        • Miscarriage
        • Pregnancy-related high blood pressure
        • Polyhydramnios
        • Preterm delivery - can lead to respiratory distress
        • Stillbirth
      • Increased risk for newborn complications
        • Breathing difficulties
        • Low blood sugar
        • Jaundice
        • Infant mortality is 30/1000 live births (4 X general population rate)
    • Poorly controlled preexisting diabetes (IDDM and NIDDM)
      • Malformations most likely to originate before 7th week gestation
      • Includes risk for:
        • Congenital heart defects (5 X average incidence)
          • Transposition of great vessels
          • VSD
          • ASD
        • Renal anomalies (5 X average incidence)
          • Renal agenesis (6 X average incidence)
          • Cystic kidney (4 X average incidence)
          • Ureter duplex (23 X average incidence)
        • Situs inversus (84 X average incidence)
        • Anal/rectal atresia (5 X average incidence)
        • Central nervous system defects
          • Neural tube defects (10 X average incidence)
          • Anencephaly (5 X average incidence)
          • Caudal regression (300 X average incidence)
    • If blood sugar levels are well controlled beginning before pregnancy, risk for complications falls to almost population risk
  • Women with IDDM prone to microvascular disease
    • Difficult for these women to carry successful pregnancy
      • Causes diabetic retinopathy, kidney disease, coronary artery disease, and nerve disease in peripheral limb structures
      • Pregnancy puts increased demand on already stressed system
    • Prevents optimal maternal-fetal blood exchange

Management of PregnancyEdit

  • Should begin monitoring blood sugar before pregnancy
    • Since most serious birth defects associated with diabetes originate in early weeks
    • Blood sugar control begun before pregnancy reduces risk of birth defects, miscarriage, stillbirth, macrosomia, and newborn complications
    • Ideally keep blood glucose levels between 60 and 120 mg/dl
  • Monthly blood test to measure glycated hemoglobin
    • Substance formed when glucose in blood attaches to protein in red blood cells
    • Test shows how well blood sugar has been controlled for up to 3 months
    • Can help determine when it is "safe" to conceive
    • Can be used to monitor control throughout pregnancy
  • Women should take multivitamin with 400 micrograms of folic acid
    • Beginning at least one month before pregnancy
    • Because women with diabetes at increased risk for NTDs
    • No studies showing that this larger dose prevents NTDs in women with preexisting diabetes
  • Women who take oral medication to control blood sugar must switch to insulin
    • Oral medications may increase risk for birth defects
    • Must be done prior to conception
  • Glucose Challenge
    • Used to screen pregnant women for gestational diabetes
    • Does not need to be offered to women under 25 years because their risk is very low
    • Consume drink with 50 grams of glucose and measure blood one hour later
    • Women with high blood levels of glucose then take glucose tolerance test
  • Glucose Tolerance Test
    • Consume drink with 100 grams of glucose
    • Blood samples drawn one, two, and three hours following to measure level of glucose
    • Identifies women with gestational diabetes who should be monitored
  • Maternal serum AFP screening
    • Since women with diabetes at increased risk to have baby with neural tube defect
    • Maternal serum AFP is elevated in all women with diabetes so must be interpreted with knowledge that woman is diabetic
  • Frequent ultrasounds to track fetal growth during 3rd trimester
    • May recommend C-section if large baby
    • "Non-stress" test to monitor baby's heart rate

Control of Diabetes During PregnancyEdit

  • Diet
    • Recommend that women get nutritional counseling
    • Diet may need to be modified as pregnancy progresses
    • As a general rule, women should consume 2,200-2,400 calories per day
  • Exercise
    • Helps control diabetes by prompting body to use insulin more efficiently
    • Recommended for women with gestational diabetes and some with preexisting diabetes
  • Insulin Treatment
    • Given to many women with preexisting diabetes
    • Requirements change during pregnancy
      • Usually increase after 20-24 weeks
      • Stabilize by 36 weeks
    • Only 10-15% of women with gestational diabetes need insulin
      • Recommended if blood sugar levels don't stabilize after two weeks of diet control
      • New oral medication being tested that has been shown to not increase risk of birth defects or complications
  • Blood sugar levels may be difficult to control after delivery
    • Especially true if woman is breastfeeding
    • Blood levels usually return to normal for women with gestational diabetes


  • American Diabetes Association
Phone: (800) 342-2383
Web: www.diabetes.org
  • March of Dimes
Phone: (800) 367-6630
Web: www.modimes.org
  • Healthy-ojas Diabetes Association
Web: http://healthy-ojas.com/diabetes/diabetes-details.html


"Diabetes in Pregnancy." March of Dimes Fact Sheet. www.modimes.org Emery AEH, and Rimoin KL, eds. Principles and Practice of Medical Genetics (1990). Rope, Alan. "Pregnancy Complicated by Diabetes Mellitus." Topics in Medical Genetics lecture (2002).


The information in this outline was last updated in July 2002.