Transcript Prevention of Birth Defects

Prevention of Birth Defects
An Overview of Primary and
Secondary Strategies
Primary Prevention
Single Gene Disorders
 No medical intervention available to
correct underlying pathology.
 Prevention is dependent upon preconceptual genetic counseling of at-risk
couples.
Primary Prevention
Teratogenic Disorders
Teratogen- any environmental influence that
adversely affects the normal development of
the fetus
 A wide variety measures are available to
protect the otherwise healthy fetus from in
utero damage.
 These include education concerning of the
mother concerning nutrition and exposure to
teratogenic agents and also
 Screening for infectious diseases.
Primary Prevention
Chromosomal Disorders
 These disorders are not systematically
predictable and risk factors are not
determined.
 Aside from pre-conceptual counseling in
cases where known risk factors are
present primary prevention strategies
are not available.
Primary Prevention
Mulifactorial disorders
 Neural tube defects including spina bifida
were linked to maternal folic acid deficiencies
in the early 1990’s.
 In 1996 folate supplementation was
recommended for women anticipating
conception or in the first trimester of
pregnancy.
 In 1998 folate supplementation was required
in grain products produced in the U.S.
Secondary Prevention of Birth
Defects
Prenatal Diagnosis
Prenatal Diagnosis
The diagnosis of a disease or a condition in a
fetus or embryo before it is born.
The decision as to whether to use prenatal
diagnostic procedures is one made as a result
of consultation between the family and the care
provider. There is no absolute requirement for
the utilization of these technologies in any
circumstance.
Prenatal Diagnosis
Candidate pregnancies for screening:
+ advanced maternal age >35
+ previous offspring that were premature or had
abnormalities
+ chromosomal abnormalities in either parent
+ parents at risk for in-born errors of
metabolism
+ high levels of maternal serum alpha
fetoprotein (AFT)
Prenatal Diagnosis Techniques
Ultrasound
Routinely done around 20 weeks
Detects structural defects
Determines gestational age and sex
No Risk
Prenatal Diagnosis
Transabdominal Amniocentesis
~ 1/4 cup of amniotic fluid removed at 16 wks.
Fluid is produced by fetal lungs, kidneys and
umbilical cord. The fluid contains shed fetal skin
cells and biochemical substances produced by the
fetus.
AFT may indicate neural tube defects
Complication rate: <5%, Miscarriage: .25-.50%
1
2
Prenatal Diagnosis
Chorionic Villi Sampling
Performed at 8-10 wks
Involves passing a small catheter through the vagina
into the uterus
Small samples of cells are taken from the placenta,
where it attaches to the wall of the uterus.
Miscarriage rate is .5 -1.0%
1