Birth Defects

1
Birth Defects

• 150,000 babies born each year with birth defects
  (3-5)
• Birth defect abnormality of structure,
  function, or metabolism present at birth that
  results in a physical or mental disability or is
  fatal.
• Birth defects are the leading cause of infant
  mortality.

2
The Quest for the Perfect Child

• Attempts to minimize birth defects
• Women having fewer children, so each one counts
• Women having children at older ages, so risk for
  defects increases
• Lorber and Moore Designer babies
• Sex selection
• Eugenics
• What is normal?

3
Fetal Quality Control

• Strother Ratcliff
• Required decisions
• Pressures to make certain decisions
• Physical intrusions
• Alteration of pregnancy experience
• Potential of loss of rights of mother as fetus
  gains rights

4
But

• Think about how far can we go?
• Which birth defects are unacceptable and which
  ones are tolerated?
• Should we encourage a woman to abort a child with
  a certain defect?

5
What Causes Birth Defects?

• Genetic
• Environmental
• Causes of 60-70 of birth defects are unknown.

6
Genetic causes

• Single abnormal gene
• Combination of genes
• Number or structure of chromosomes
• Missing or extra chromosome

7
Environmental Causes

• Drug or alcohol abuse
• Exposure to medications (Accutane, thalidomide)
• Infections

8
Multifactorial Inheritance

• Genes environment
• Cleft lip/palate
• Club foot
• Some heart defects

9
Diagnosing birth defects

• Prenatal genetic testing is available, although
  no test is 100 accurate.
• Counseling parents about the risks and choices.
• Choices
• Continue pregnancy and arrange treatment at the
  time of delivery
• Fetal surgery
• abortion

10
Prenatal Genetic Testing

• Testing recommended if
• You are 35 or older when the baby is due
• You have a family history of birth defects
• You have a child with a birth defect
• You have type 1 diabetes prior to your pregnancy

11
The Type of Testing

• And what it can reveal depends on the weeks
  gestation of the pregnancy
• Some are more invasive tests than others
• Some depend on maternal blood samples,
  ultrasound, amniotic fluid, tissue samples

12
First trimester

• Between 11th and 14th weeks of pregnancy
• Maternal blood test to detect increased risk of
  Down Syndrome. It detects levels of HCG (a
  hormone, human chorionic gonadotropin) and
• PAPP-A (pregnancy associated plasma protein a).
• May detect heart defects or skeletal problems
• Blood test combined with ultrasoundsound waves
  create an image of the baby. Measures region
  under the skin behind the babys neck.

13
First Trimester Screen

• At 11th week, identifies 87 of babies with Down
  Syndrome.
• At 13th week, identifies only 82.
• False positives are possible, so women need more
  testing.
• 1 in 20 have positive result on these two tests
  during the first trimester.
• Followup is usually CVS

14
CVS

• Chorionic villus sampling (9-14 weeks)
• Sample of placenta is extracted and tested for
  genetic abnormalities. Results in 2-7 days
• Ultrasound guided needle through uterus or
  catheter through cervix
• Risk of miscarriage is 1
• Does not screen for open spine defects
• Balance early diagnosis vs. increased risk

15
Quad Marker Screen

• Maternal blood screening weeks 15-20 of pregnancy
  to detect Down Syndrome and open spine disorders
  like Spina Bifida
• Alpha-fetoprotein
• human chorionic gonadotropin
• estriol
• Inhibin-Aa hormone produced by placenta
• 1 in 20 false positive rate
• Usually do ultrasound and amnio

16
Amnio

• Amniocentesis (15-18 weeks)
• Risks of fetal loss 0.5 (1 in 200) when done
  prior to 24th week
• Sample of amniotic fluid is drawn from womans
  abdomen using ultrasound guidance
• Results in 2 weeks
• Also used at 36 weeks to check lung maturity

17
Bozzette Argues

• Along with the ability for rapid and early
  detection of congenital and hereditary disorders
  comes a responsibility to provide information and
  emotional support for families faced with the
  reality of disease and disability.

18
Bozzette

• Many issues remain unanswered such as to whom
  genetic testing should be made available and how
  much of this technique should become routine in
  prenatal care.

19
Age for genetic testing

• Keeps creeping down.
• It used to be 35 and over
• Now it is 25-30.
• What are the implications?

20
Risks for Defects by Age

• Chance of carrying an abnormal child
• 35 years old 1 in 2,000
• 39 years old 1 in 100
• 44 years old 1 in 20