Hesperian Health Guides

Chapter 12: Common Birth Defects

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Types of Birth Defects

One out of every 100 or so babies is born with some kind of obvious defect or deformity. There are many different types. In this chapter we describe a few of the most common: cleft lip and cleft palate, extra or joined fingers or toes, and short, missing, or deformed limbs. We also discuss children born with multiple contractures (arthrogryposis). Please also refer to the chapters on club feet (Chapter 11), and spina bifida (Chapter 22).


In many cases, the cause of a birth defect is not known. But sometimes a defect may be caused by one of the following:

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The mother of this girl with cleft lip and palate did not get enough to eat while she was pregnant.
child with deformed limbs
A doctor gave this boy’s mother a medicine for ‘morning sickness’.
child's arm with grooves and deformed fingers
child with Down syndrome
This boy’s mother was 45 years old when he was born.
  • Poor nutrition during early pregnancy. This is thought to be one cause of cleft lip and palate.
  • Genetic (hereditary). Sometimes certain defects run in families. For example, if one parent was born with an extra thumb, there is a greater chance that a child will be born with a similar defect. One or both parents may be ‘carriers’ of the factor that causes a defect, without having it themselves. However, it may be present in relatives. Often both parents must have a ‘defect factor’ for a child to be born with the defect. For this reason, birth defects are more common in children whose parents are closely related, and who therefore carry the same defect factors.
  • Medicines, pesticides, chemicals, polution, and poisons. Especially during the first 3 months of development, a baby in the womb can easily be harmed by chemicals and poisons. Many medicines, drugs, and pesticides (plant, insect, and rat poisons) can cause birth defects if a pregnant mother is exposed to them.
  • German measles (rubella). If the mother gets German measles during the first 3 months of pregnancy, it can cause defects in the baby. These usually affect the senses (hearing and seeing), the brain (cerebral palsy and mental slowness), or organs inside the body (heart, liver). Sometimes the baby is born with ‘rubber band-like’ grooves on the limbs and deformed or missing fingers or limbs.
  • Children born to mothers 40 years of age or older are more likely to have Down syndrome and defects of the hands, feet, or organs inside the body (heart, liver). In this age group, about 1 mother in 50 will have a child born with Down syndrome or defects. If both parents are this age, the chance is even more.

See ways to prevent birth defects.

This page was updated:21 Nov 2019