Easy Guide To: Understanding Genetic Defects

Birth Defect Guide


Birth Defects


What Are Birth Defects?
What Are The Most Common Causes?
What Are The Most Common Types?
Can They Be Prevented?
How Are They Detected?
What Are The Chances of Having a Baby with a Birth Defect?


Genetic Disorders
Genetic Testing
Pregnancy Complications
Prenatal Care
Paternity Testing

Birth Defects Overview

Cleft Palate
Cystic Fibrosis
Down Syndrome
Spina Bifida

What Are Birth Defects?

Also called congenital defects, birth defects are abnormalities which are detectable at birth or early infancy. They range from minor abnormalities such as birthmarks to serious disorders such as spina bifida and Down syndrome. There are more than 4,000 known defects, and although many can be cured or treated, they are the leading cause of death in the first year of a baby's life. For the majority of women, pregnancy progresses well except for some minor but annoying pregnancy symptoms such as morning sickness, swollen hands or feet or varicose veins during pregnancy. However in a certain percentage of pregnancies there will be structural defects or abnormal developments in the fetus. These can occur in isolation or as a result of a genetic syndrome or chromosomal problem. Birth defects can be caused by a number of factors, including genetical and environmental ones, although in many cases no obvious cause can be found. Usually issues can be highlighted in the first and second trimester pregnancy ultrasound scans (combined with more invasive diagnostic tests like a chorionic villus sampling or amniocentesis test); although some defects may only be noticed after birth, such as blindness or deafness. Most birth defects happen within the first 3 months of conception. While some, such as cleft lip/palate can be treated very easily after birth, others are more serious and even life threatening.

What Are The Most Common Causes?

Chromosome Defects
Some babies are born with more or fewer than the normal 23 chromosomes (the delicate material which carries our genetic structure). Chromosomal abnormalities can lead to conditions like Down syndrome, Patau’s syndrome and Edward’s syndrome.

Genetic or Hereditary Defects
These defects are caused by genetic disorders which have been inherited from either or both parents. Common defects include albinism (lack of color pigment in the hair or eyes) and achondroplasia (dwarfism).

Drugs and Harmful Chemicals
Certain drugs and chemicals (known as teratogens) can damage a fetus if the mother is exposed to them while pregnant. Thalidomide used to be prescribed in the 1970s for morning sickness and resulted in some terrible deformities. Another teratogen includes isotretinoin which is used to treat acne. Alcohol abuse can also affect the development of a baby's brain (fetal alcohol syndrome).

X Rays
If an embryo is exposed to X-rays at the early stage of development, (maybe before a woman knows she is pregnant) this can cause abnormalities. This is why preparing for pregnancy and following a prenatal care guide is so important.

Certain infections in the mother during pregnancy can increase the chance of birth defects. Particularly dangerous infections include rubella (German measles) and toxoplasmosis (caught from cat's feces).

Fortunately there is no clear evidence that smoking prior to conception can harm a fetus, but smoking during pregnancy can be devastating to a baby and cause pregnancy complications. It can cause ectopic pregnancy, preeclampsia, abnormal placental implantation, premature placental detachment, premature rupture and even premature birth. Babies of smokers are more likely to be born shorter, with a smaller head circumference, with cleft palate, or lip and heart defects (see congestive heart failure). They are also more likely to develop SID (sudden infant death syndrome).

Illegal Drug Use
Fortunately there is little evidence that drug use before pregnancy can cause damage to any future fetus. However, drug use during pregnancy can lead to birth defects, premature labor and lower IQ scores in later childhood.

What Are The Most Common Types?

Face & Mouth
Cleft palate and cleft lip, according to the Centers for Disease Control (CDC) are the most common birth defects. Every year in America 6,700 babies are born with one or both of these treatable conditions.

Down Syndrome
A genetic condition which is second on the CDC birth defect list. Just over 5,400 babies per year are born with Down syndrome in America.

Musculoskeletal Defects
Hand, leg, arms or feet defects (where a finger or toe may be missing). The CDC reports just fewer than 5,800 defects per year. Clubfoot occurs once in every 1,000 pregnancies.

Stomach Abnormalities
Defects of the stomach wall like omphalocele or gastroschisis can be treated successfully by operation after birth (as long as they are not associated with other defects). This also applies to defects of the digestive system. The CDC reports 2,800 babies are born each year with stomach/intestinal defects. See also, diagram of the human body.

Defects of the heart are one of the most common types of defects but they can be difficult to detect by prenatal scans. A congenital heart defect (which means present from birth) can affect different parts of the heart including the valves, chambers or blood vessels. One of the most common causes of heart defects is if the mother develops rubella during pregnancy. Hereditary factors seem to be less significant but still play a role. If a parent has a congenital defect their child is at increased risk. However, if the couple has one affected child, the second child is less likely to have a defect.

Spina Bifida
This condition can vary in severity. Severe defects of the spine can be highlighted by a routine anatomy scan, sometimes quite early in pregnancy. A simple blood test (triple screen test) which tests the mother's blood for elevated levels of alpha-fetoprotein, may give an earlier indication of spina bifida, in which case a scan would be carried out straight away. See genetic testing during pregnancy.

Head and Spine
Anencephaly is a severe structural defect of the brain where part of the brain is missing completely. Life after birth is impossible for any extended period of time and there is no 'cure'. An ultrasound scan can usually detect this problem early in a pregnancy.

Other Conditions
Eye defects, hydrocephaly (water in the brain), malformations of the kidneys or urinary tract.

Functional Birth Defects
These are related to how the body functions, and can lead to disabilities later in a child's life including: learning disabilities, autism, blindness, cataracts and metabolic disorders. It also refers to degenerative disorders such as Rett syndrome, muscular dystrophy and lysosomal disorders.

Can They Be Prevented?

Some birth defects can be prevented or the risks of them occuring reduced. Immunization before pregnancy is important for diseases such as rubella. You can also take precautions by taking folic acid before and during pregnancy, and by avoiding teratogens and X-Rays during pregnancy. Some defects are related to genetic conditioning. Some couples feel reassured by talking to genetic counselors before becoming pregnant. For a general guide to expecting a baby, see our pregnancy guide.

How Are They Detected?

Birth defects take place before a baby is born, usually in the first 3 months or first trimester of pregnancy. Most pregnant women receive a first and second trimester scan which can pick up any of the major abnormalities. However women over 35, women with genetic conditions, women with diabetes before pregnancy or women who have given birth to child already with a birth defect may be offered more specific tests. Talk to your doctor about which scans are right for you.

What Are The Chances of Having a Baby with a Birth Defect?

Statistically, 3 in every 100 babies in America are born with birth defects. Risks are higher for women experiencing a pregnancy after 35 and for those who smoke, drink or take certain drugs during pregnancy. Those with a history of genetic disorders in the family should talk to a genetic counselor. A geneticist will help evaluate the likelihood of having a baby with a condition.

Interesting Research Statistics. In America every year:
• 467,201 babies are born prematurely.
• 307,030 babies are born with low birth weight.
• 154,051 children are born with birth defects.

Useful Articles
Prenatal tests: Routine and non-routine tests.
Genetic testing before pregnancy: Know your risks.
Aspirin during pregnancy Avoid unless prescribed by your OB/GYN.

  Related Articles on BIRTH DEFECTS

For other useful information, see the following:
The female body and the human body.
Development of the female body: from puberty to menopause.
Hospital departments explained: A to Z of departments.
Recommended health screenings for women: For each life stage.
Main causes of death in women: Top 10 diseases that kill women.

Back to Homepage: Womens Health Advice

Please Note: Information provided on this site is no substitute for professional medical help. See Disclaimer.
Copyright. All rights reserved.