A Guide to Pregnancy Complications

Birth Defects

All expectant parents dream of having normal, healthy children. Unfortunately, sometimes this does not happen. Although most babies are born normal and whole, about 3 percent are born with some form of abnormality. Fortunately, about half of these imperfect babies have only minor defects that can be easily corrected, leaving no trace. In the other half, however, the defect may be severe and even life-threatening.


Birth defects, also called congenital anomalies, can affect nearly every organ of the baby's body. In some cases, these defects are visible on the surface of the body; in other cases, the defects involve internal organs, such as the heart or intestines. Another type of defect, called an inborn error of metabolism, is not visible but rather is an abnormality of the chemical system of the body in which normal chemical reactions in certain organs cannot occur.


The following is a list of the most common serious birth defects:

  • Head and face: Hydrocephalus (an abnormally large head due to accumulation of fluid), microcephaly (an abnormally small head), cleft lip and cleft palate (an abnormal opening in the lip and the roof of the mouth)
  • Heart: Congenital heart disease (a variety of different defects in the valves and walls of the heart)
  • Lungs: Absence of one lung, abnormal lung development
  • Stomach and intestines: Abnormal blockage
  • Abdominal wall: An opening through the navel or a large defect that causes the intestines to protrude
  • Kidneys: Absence of one or both kidneys, large cysts in the kidneys, developmental abnormalities of the kidneys (such as variations in structure)
  • Back: Spina bifida (an abnormal opening in the backbone in which nerves are contained in a thin, saclike structure)
  • Arms and legs: Absence of fingers or toes, fused fingers or toes, total absence of an arm or leg, clubfoot (an abnormal inward turning of the foot)


Little is known about the cause of most congenital anomalies. Heredity plays a role in some cases; some families have several members with similar abnormalities. Certain drugs, environmental pollutants, toxins, and high doses of radiation cause specific abnormalities. Certain infections in the mother -- the most significant of these is German measles (rubella) -- may cause multiple severe abnormalities. The mother's heavy drinking during pregnancy can cause fetal alcohol syndrome. In most cases, however, the exact reason for the abnormality is not known and probably derives from a disturbance in the normal organ development of the fetus.


The ability to detect congenital abnormalities before birth is a relatively recent medical achievement. In addition to allowing some couples to terminate an abnormal pregnancy, it has enabled others who may be at risk of having abnormal offspring to continue a pregnancy knowing the fetus is normal.

During the first prenatal visit, the doctor obtains a thorough history of both parents, including age, race, ethnic background, and previous abnormal conditions in the family. This information is used to determine if testing for an abnormal fetus is necessary. The following tests detect specific abnormalities:

  • Ultrasonography: detects hydrocephalus, microcephaly, spina bifida, tumors, heart defects, intestinal blockage, and absence of an arm or leg.
  • Blood tests: The alpha-fetoprotein (AFP) test (the most commonly used blood test to detect fetal abnormality) helps detect spina bifida.
  • Amniocentesis: detects chromosome abnormalities, spina bifida, and nearly 100 chemical disorders in the fetus.
  • Chorionic villus sampling (CVS): detects the same chromosomal abnormalities as amniocentesis, but the test can be performed earlier in the pregnancy.


Once an abnormality of the fetus has been detected, the parents must make a decision to either terminate or continue the pregnancy. However, the many remarkable advances in medical and surgical care can wholly cure many birth abnormalities considered very serious a few decades ago. Many heart defects, intestinal obstructions, and abnormalities of the abdominal wall can be corrected surgically, and those children born with them can expect to lead normal and healthy lives.

A pediatrician and a surgeon should describe to the parents the extent of the fetal abnormality and the chances of correcting it. Research currently underway may eventually enable surgical correction of certain types of congenital abnormalities while the fetus is still in the uterus.

Future Pregnancies

Fortunately, in most cases, birth defects do not repeat themselves in future pregnancies. Parents with one abnormal child have an average risk of less than 5 percent of having another child with the same abnormality. If, however, the defect is thought to be inherited from one parent, a specific pattern of this abnormality may be repeating itself. Before the parents of an abnormal child plan another pregnancy, they should meet with a doctor skilled in genetics and fetal abnormalities to discuss the risks of abnormalities appearing again.

Effect on the Parents

The birth of a physically abnormal child can produce feelings of shock, disbelief, sadness, and even anger in the parents. All members of the family are in some way affected by the birth. The parents must create a mutual support system to cope with this crisis. Gradually, the parents resolve their grief and become as closely attached to this child as they would to any other.

Genes, disease, and alcohol use can all contribute to abnormal development of a fetus. Continue reading to find out how a fetus also can be affected if its blood is incompatible with the mother's.