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Prenatal diagnosis and counseling (Invasive prenatal diagnosis…
Prenatal diagnosis and counseling
Methods leading to complete assessment of fetal anatomic and physiologic development, to detect fetal deseases and malformations, and to intrauterine monitoring of the fetus
Frequency of fetal malformations in live born neonates app. 2-3%
Congenital abnormalities
chromosomal abnormalities
monogenic diseases
malformations: teratogens, multifactorial condidions
Teratogens
factors, which can cause irreversible disorder of structure or function of the fetus is exposed before delivery
Physical factors: Ionizing radiation, Extremal temperatures, Ultrasonic vaves
The rarest reasons of malformations are physical and chemical factors
Environmental factors
Maternal diseases: Diabetes (glucose levels), Phenylketonuria
Malnutrition
folic acid deficiency – neural tube defects,
vitamin A deficiency – xerophtalmia, hypotrophy, CNS malformations, preterm delivery
Maternal infections – TORCH
Toxoplasmosis
Others – syphilis, varicella zoster, influenza
Rubella – Gregg’s triad: eye defects (cataract, glaucoma), hearing problems (deafness), heart defects
Cytomegaly – microcephaly, hydrocephaly
Herpes
Chemical factors
Medicines
Thalidomid – phocomelia and amelia
Non-steroid antiinflammatory drugs – preterm closure of ductus arteriosus
Lithium, Folic acid antagonists – wady OUN
Retinoids – cranio-facial defects
Oral anticoagulants (warfarin) – hypoplasia and abnormal calcification of long bones epiphyses, intrauterine growth restriction
Drugs
Cocain – preterm placental abruptio, fetal loss, microcephaly, limb malformations, mental delay
Alcohol – FAS
Hormons
Diethylstilbestrol – vaginal adenocarcinoma, clear-cell carcinoma
Purposes of prenatal diagnosis
information of the defect, enabling the future parents to prepare for the handicapped child,
monitoring of the fetus and progression of the malformations,
planning pre- and perinatal management,
labor in the most appropriate conditions,
next pregnancy planning.
Methods of prenatal diagnosis
ultrasonography,
biochemical screening
free fetal DNA in maternal circulation
CVS (chorion villus sampling)
amniocentesis
cordocentesis
Biochemical screening
AFP (alpha-fetoprotein) --> fetal urine--> amniotic fluid--> diffusion to maternal circulation / swallowing by the fetus
AFP level:
Trisomy 21: 72%of values for healthy pregnancies
NTD (neural tube defects, defects of abdominal wall, gastrointestinal tract): At least doubled
„double test” 8-14 weeks: PAPP-A, beta-hCG
„triple test” 15-22 weeks: hCG, uE3 (fE3), AFP
Double test:
PAPP-A – decreased in trisomies 13, 18, 21
beta-hCG – decreased in trisomies 13 and 18, increased in trisomy 21
Triple test:
beta-hCG – decreased in trisomies 13 and 18, increased in trisomy 21
free estriol – decreased in trisomies 18 and 21, normal in trisomy 13
AFP – decreased in trisomies 18 and 21, normal in trisomy 13
Before blood sampling ultrasound examination should be performed – gestational age and number of fetuses are essential to calculate MoM.
Fetal DNA in maternal circulation
Screening test assesing risk, but:
99,9% of aneuploidies are in high risk group, there is less than 1% of false positive results
Invasive prenatal diagnosis
Indications
age above 35 (37) years
high risk in screening test
fetal malformations found in US
previous child with chromosomal abnormality
genetic disease in family
balanced translocation in one of the parents
Fetal malformations or IUGR in the 2nd trimester – are frequently correlated to the chromosomal abnormalities.
Previous child with chromosomal abnormality – risk of recurrence is 1%.
Genetic diseases
cystic fibrosis,
Huntington chorea
muscular dystrophies,
metabolic diseases.
CVS - (chorionic villous sampling)
8 - 12 weeks
transcervical or transabdominal
fetal karyotyping
no biochemical tests
high complication rate (3%)
early obtained result (7 - 10 days after CVS – before 12 weeks)
Amniocentesis
14 - 18 weeks
transabdominal
withdrawal of maximum 1/10 amniotic fluid volume
low complications rate (1%)
possibility of biochemical tests
Cordocentesis
later than 18 weeks
umbilical vein blood sampling
quick result
technically difficult
high risk of complications (3%)
If the patient is Rh negative, 300 μg anti RhD immunoglobuline should be administered after procedure to prevent immunization
Contraindicatons
1) coagulation dysfunctions
2) threatened abortion
3) retroplacental hematoma in US
4) infectious changes in the abdominal skin
Complications
1) amniotic fluid leakage,
2) intrauterine infection,
3) spotting / bleeding,
4) fetal demise,
5) abortion.
Screening in pregnancy --> Low risk --> Healthy fetus
Screening in pregnancy--> High risk--> Fetal defect--> Conservative management / Intrauterine treatment / Termination of pregnancy
Immunizations
Intrapartum
safe: tetanus toxoid, diphtheria, influenza, hepatitis B, pertussis
avoid live vaccines (risk of placental and fetal infection): polio, measles/mumps/rubella, varicella
contraindicated: oral typhoid
Radiation in Pregnancy
Necessary amount to cause miscarriage: >5 rads
Necessary amount to cause malformations: >20-30 rads