What causes congenital anomalies?

From the Guidelines

Congenital defects are primarily caused by a combination of genetic factors, environmental exposures, and maternal health conditions during pregnancy, with the most recent evidence suggesting that proximity to unconventional oil and natural gas sites may also increase the risk of congenital heart defects 1. The causes of congenital defects can be multifaceted, including:

• Genetic factors such as chromosomal abnormalities, single gene mutations, and complex genetic interactions
• Environmental exposures like maternal infections, certain medications, alcohol consumption, tobacco use, and illicit drug exposure during pregnancy
• Nutritional deficiencies, particularly folate deficiency, which increases the risk of neural tube defects
• Maternal health conditions, such as diabetes and phenylketonuria, when poorly controlled during pregnancy
• Exposure to environmental toxins, including lead, mercury, and certain pesticides A recent study found that living in proximity to unconventional oil and natural gas sites may increase the risk of congenital heart defects in newborns, with adjusted odds ratios ranging from 1.04 to 2.62 1. Additionally, seizure disorders in pregnant women, whether treated or untreated, can also increase the risk of congenital anomalies, including neural tube defects, highlighting the importance of preconception counseling and care, including supplementation with 4 mg of folic acid daily 1. Preventive measures, such as taking prenatal vitamins with folic acid, avoiding known teratogens, managing chronic health conditions, and receiving appropriate vaccinations before pregnancy, can help reduce the risk of congenital defects.

From the Research

Causes of Congenital Defects

• Congenital defects can be caused by a combination of genetic and environmental factors, including nutritional deficiencies and exposure to toxins 2, 3
• Folic acid deficiency is a known risk factor for neural tube defects (NTDs), and supplementation with folic acid has been shown to reduce the risk of NTDs 4, 2
• Other potential causes of congenital defects include:
  • Genetic mutations 5, 6
  • Environmental exposure to toxins, such as alcohol and cigarette smoke 3
  • Maternal factors, such as diet, body mass index (BMI), and age 5
  • Vitamin B12 deficiency 5

Role of Folic Acid and Vitamin B12

• Folic acid supplementation has been shown to reduce the risk of NTDs, particularly in women who are planning to become pregnant 4, 2
• Vitamin B12 deficiency has also been linked to an increased risk of NTDs, and supplementation with vitamin B12 may be beneficial in preventing these defects 5
• The exact mechanism by which folic acid and vitamin B12 exert their beneficial effects is not fully understood, but it is thought to involve interactions with genetic and environmental factors 6

Genetic Risk Factors

• Genetic variants, such as those in the GIF, LRP2, CUBN, TCb1R, and MTHFR genes, have been linked to an increased risk of NTDs 5, 6
• Research is ongoing to identify other genetic risk factors and to understand how they interact with environmental factors to cause congenital defects 6