Ultrasound Guided Intervention in Pregnancy
· Amniocentesis (diagnostic)- ( Indications) Early pregnancy — genetic:
maternal age, previous chromosomal anomaly, balanced translocation, determine sex in sex linked disorders, fetal anomalies with a high association with chromosomal abnormality.
Inherited metabolic disorders — previous history/family history, racial group.
Raised maternal AFP when no fetal abnormality detected and Finnish nephrosis suspected.
Late pregnancy — to investigate extent of Rh isoimmunization, to determine fetal lung maturity,
lecithin:sphingomyelin ratio and phosphatidyiglycerol.
(Risk)- Fetal — fetomaternal hemorrhage, orthopedic deformities related to membrane rupture, increased risk of RDS, 1% chance of miscarriage/intrauterine death or preterm delivery. Fetal damage should be avoided by ultrasound guidance. Maternal — infection, amniotic leak; organ damage should be avoided by US guidance.
· Amniocentesis for volume reduction in PH- To relieve maternal distress caused by PH and prevent or treat preterm labor. Placental abruption and rupture of membranes have been reported as complications.
· Amniocentesis for volume reduction in 'stuck twin'- Amniocentesis for PH of the recipient twin improves prognosis in both the recipient and oligohydramniotic ‘stuck twin’.
· Amniocentesis for pharmacologic intervention- Intra-amniotic drugs may be administered for cardiac arrhythmias (digitalis agents) or hypothyroid fetal goitre (thyroxine).
· Chorionic villus sampling- First trimester alternative to amniocentesis performed between 10th and 12th weeks for cytogenetic, biochemical and molecular prenatal diagnoses.
(indications)- Maternal age 35 or over. Previous offspring with chromosomal trisomy, parent carrier of chromosomal translocation, fetus at risk of an X-linked or metabolic/bio chemical disorder. Screen positive on serum screening AFP/BhCC Abnormality on first trimesters ultrasound associated with karyotypic abnormality.
(Limitations)- Transabdominal approach loss rate approximately 1.5-2.5% by experienced operators. Mosaicism from the placenta may necessitate fetal blood sample.
· Percutaneous umbilical blood sampling- (indications) Blood group, hematocrit determination, transfusion, karyotyping (anomalies, severe IUGR), transplacental infections, SLE, blood gas analysis in severe IUGR, hematological abnormalities, enzyme deficiency, blood chemistry (thyroxine in fetal goitre), hereditary immune deficiency and Duchenne’s muscular dystrophy.
(Complications) - Fetal loss approx 1%. Cord hematoma and arterial spasm. Fetal movement can be abolished by pancuronium bromide.
· Fetal transfusion/intravascular therapy- Abnormal fetal fluid collections may be aspirated for diagnostic or therapeutic reasons; fetal spaces can be decompressed into the amniotic cavity by a double pigtail catheter placement (bladder outflow obstruction, pleural effusions).
· Selective termination- This may be performed in multiple pregnancy to selectively reduce fetal number, or to selectively terminate an abnormal fetus. Selective termination can be performed by ultrasound guided intracardiac lethal injection of potassium chloride; 30% of patients lose the entire pregnancy.
· Fetal biopsy
- Skin and liver biopsy (congenital enzyme deficiency congenital ichthyosis). Rarely fetal tumors can be biopsied if the histology will alter obstetric management.