The goal is to repeat, by examining a large number of chromosomal abnormalities in the unborn child, if it shows malformation risk factors or signs making fear: nuchal thickening of the neck to ultrasonography or hCG levels too high.
With a mother aged (over 38 years with a positive test HT21) for example, it allows to perform a fetal karyotype.
A practical limitation in case of risk of spontaneous abortion and placental malabsorption.
20 mL sample of amniotic fluid to analyze and can be cultured amniocytes.
Without anesthesia, outpatient examination begins with an ultrasound location of the placenta and verification of fetal vitality.
Possible from the 15th week of gestation, the puncture is transabdominal ultrasound-guided needle in.
20 ml liquid enough for the exam.
The collected amniotic fluid is cultured, and amniocytes are analyzed.
The karyotype is established by the cytogenetics laboratory within 15 to 20 days, and a map of the observed genetic abnormalities.
There are rare under ultrasound but may exist as:
– A white puncture bringing not liquid;
– A bloody puncture wound through the placenta;
– Especially a risk of miscarriage: 0.5 to 1% of cases.
K15 + K10 + B120 and B1300 for additional dosage of alpha-fetoprotein.
On suspicion of spina bifida (malformation family history or as Depakine mother during pregnancy) may be added a dose of alpha-fetoprotein, alkaline phosphatase and its isoenzymes for research of cystic fibrosis.
Determining the sex of the fetus is also possible for conditions related to fetal sex.