Birth Defects, causes and prevention

Birth Defects, causes and prevention
Image taken from CDC


Birth defects which are also known as congenital anomalies can be defined as structural or functional abnormalities that also include metabolic disorders, which are present from birth. It can also be defined as any structural or functional abnormality determined by factors operating largely before conception or during gestation.  The birth defect can cause spontaneous abortions and stillbirths as well as mortality and lifelong morbidity for those born with birth defects.

Worldwide, at least 7.9 million people are born each year with a birth defect.  There are more than 7,000 kinds of birth defects known to date. Of the children who are affected by birth defects, at least 3.3 million worldwide die each year before age 5 and those who survive, about 3.2 million will be mentally or physically disabled for life. Only some of the defects can be mitigated with appropriate care.

The exact cause of birth defects has been a mystery; however, there are some important contributing factors such as; genetic factors, environmental factors and complex genetic factors.

The common cause of Birth Defects

It is estimated that about 94% of severe congenital anomalies occur in low- and middle- income countries. Most birth defects occur in the first 3 months of pregnancy when the organs of the baby are forming. Main contributing factors are:

Genetic factor:

Genetic factor accounts for about 25-30 % of total birth defects, approximately 1 percent of all births are characterized by a mutation at a single genetic locus. Usually, there are no previously affected relatives. This is the case with lethal autosomal dominant traits, which typically arise as a result of a fresh mutation in the oocyte or sperm. Not all mutant genes manifest at birth or lead to structural malformations. In a simple word; The mother or father may pass on genetic abnormalities to their baby. Abnormalities occur when a gene becomes flawed due to a mutation, or change. These defects happen mostly at conception and often can’t be prevented.

Environment factors:

Environmental factors account for 5-10 % of total birth defects. Environmental factors include nutritional deficiencies maternal illness, infectious agents, and teratogenic drugs. Some of the other factors also include certain medical conditions, such as being obese or having uncontrolled diabetes before and during pregnancy. In some cases being an older mother, typically over the age of 34 years also causes a birth defect.

Types of birth defects

Structural Birth Defects:

They are the defects that are related to a problem with the structure of body parts. They include:

  • Heart defects, such as missing or misshaped valves
  • Cleft lip or cleft palate
  • Abnormal limbs, such as club foot
  • Neural tube defects, such as spina bifida, and problems related to the growth and development of the brain and spinal cord.

Functional or developmental Birth Defects:

  • Nervous system or brain problems: eg. Down syndrome, Fragile X syndrome, and Prader-Will syndrome.
  • Sensor problems: includes hearing loss and visual problems such as deafness or blindness.
  • Metabolic disorders include some chemical reactions in the body e.g. phenylketonuria and hypothyroidism.
  • Degenerative disorders: e.g. muscular dystrophy and X-linked adrenoleukodystrophy.

Preventive methods for Birth defects

All birth defects cannot be avoided but some can be prevented by prenatal care, by avoiding substances that could cause birth defects. Some of the preventive methods are:

  • While planning pregnancy, see a doctor in regular basis, start prenatal care as soon as you feel like you are pregnant. Major birth defects can be prevented by consuming Folic acid as directed by the physician and as the body required.
  • Obtain genetic counseling and birth defect screening, particularly if you have any family history of birth defects or if you are 35 years of age or older.
  • Avoid harmful substances like smoking, drinking alcohol and other drugs.
  • Keep a healthy lifestyle, keep diabetes under control, maintain a healthy weight



  12. Weinhold B. Environmental Factors in Birth Defects: What We Need to Know. Environmental Health Perspectives. 2009;117(10):A440-A447.
  13. Institute of Medicine (US) Committee on Improving Birth Outcomes; Bale JR, Stoll BJ, Lucas AO, editors. Reducing Birth Defects: Meeting the Challenge in the Developing World. Washington (DC): National Academies Press (US); 2003. 1, Introduction.