Birth Defects
Source: MedlinePlus Health Topics, U.S. National Library of Medicine
What are birth defects? A birth defect is a problem that happens while a baby is developing in the mother's body. Most birth defects happen during the first 3 months of pregnancy. One out of every 33 babies in the United States is born with a birth defect. A birth defect may affect how the body looks, works, or both. Some birth defects like cleft lip or neural tube defects are structural problems that can be easy to see. Others, like heart disease , are found using special tests. Birth defects can range from mild to severe. How a birth defect affects a child's life depends mostly on which organ or body part is involved and how severe the defect is. What causes birth defects? For some birth defects, researchers know the cause. But for many birth defects, the exact cause is unknown. Researchers think that most birth defects are caused by a complex mix of factors, which can include: Genetics. One or more genes might have a change or mutation that prevents them from working properly. For example, this happens in Fragile X syndrome . With some defects, a gene or part of the gene might be missing. Chromosomal problems. In some cases, a chromosome or part of a chromosome might be missing. This is what happens in Turner syndrome . In other cases, such as with Down syndrome , the child has an extra chromosome. Exposures to medicines , chemicals, or other toxic substances . For example, alcohol misuse can cause fetal alcohol spectrum disorders . Infections during pregnancy . For example, infection with Zika virus during pregnancy can cause a serious defect in the brain . Lack of certain nutrients. Not getting enough folic acid before and during pregnancy is a key factor in causing neural tube defects. Who is at risk of having a baby with birth defects? Certain factors may increase the chances of having a baby with a birth defect, such as: Smoking, drinking alcohol, or taking certain "street" drugs during pregnancy Having certain medical conditions, such as obesity or uncontro