Fetal abnormalities with diabetes during pregnancy

Diabetes during pregnancy is a leading cause which can results many fetal abnormalities/problems
1. Miscarriages
2. Birth defects
3. Growth restriction
4. Growth acceleration
5. Fetal obesity
6. Central obesity
Miscarriages
There is a strong association between the degree of blood sugar control prior to pregnancy and the miscarriage rate. Poor blood sugar control may double the miscarriage rates. Patients with long-standing diabetes (glycohemoglobin,HbAc , exceeding 11%) have been shown to have miscarriage rates of up to 44%. Conversely, recent reports demonstrate a normalization of the miscarriage rate with excellent glycemic control.

Birth defects

The occurrence of birth defects in normal population is 1-2%. But the likelihood of structural abnormalities in fetus of diabetic mothers is increased 4-8 folds. Most lesions involve the central nervous and cardiovascular systems. The periconceptional glycemic control is the main factor in the genesis of diabetes-associated birth defects.

1. cardiac malformations(ASD, PDA, VSD)
2. Neural tube defects
3. sacral agenesis
4. hypoplastic left colon

Growth restriction

Usually fetuses with diabetic mothers are macrosomic but there is a risk of Intra Uterine Growth restriction (IUGR) as well. The risk is three fold as compared to fetuses of non diabetic mothers. The risk is higher when the diabetes is preexisting.
The most import predictor of fetal growth restriction is underlying maternal vascular disease. Specifically, pregnant patients with diabetes-associated retinal or renal vasculopathies and/or chronic hypertension are most at risk for growth restriction.
Growth acceleration
Excessive body fat stores, stimulated by excessive glucose delivery during diabetic pregnancy, often extend into childhood and adult life. The adverse downstream effects of deranged maternal metabolism have been documented well into puberty. Glucose intolerance and higher serum insulin levels are more frequent in offspring of diabetic mothers compared with normal controls. By age 10-16 years, offspring of diabetic mothers have a 19.3% rate of impaired glucose intolerance.
Fetal obesity

Macrosomia is typically defined as a birth weight above the 90th percentile for gestational age or greater than 4000 g. In pregnant diabetic women, macrosomia occurs in 15-45% of cases, a 3-fold increase from normoglycemic controls. The infants of diabetic mothers (IDMs) had 5-fold higher rates of severe hypoglycemia, a 4-fold increase in macrosomia, and a doubled increase in neonatal jaundice. Birth injury, including shoulder dystocia and brachial plexus trauma, is more common among IDMs, and macrosomic fetuses are at the highest risk.

Central obesity

The macrosomic fetus develops a unique pattern of overgrowth, involving central deposition of subcutaneous fat in the abdominal and interscapular areas. Skeletal growth is largely unaffected. Neonates of diabetic mothers have a larger shoulder and extremity circumference, a decreased head-to-shoulder ratio, significantly higher body fat, and thicker upper extremity skin folds compared with nondiabetic control infants of similar weights.