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Fetal Medicine
Fetal medicine is an evolving branch of obstetrics which deals with unborn child to achieve ultimate aim of having healthy mother and healthy baby.
The incidence of fetal structural defect in general population is around 3%, where as the risk of chromosomal defect is 6/1000 birth among population without any risk factor
This branch of medicine, deals with prenatal screening of fetus [unborn child] for structural and genetic defects.
Ultrasound
Every pregnant women should be advised anomaly scan (ultrasonography ) during fifth month of pregnancy to rule out any major structural defect in fetus.
ROLE OF ULTRASOUND DURING PREGNANCY –
- To confirm number of fetus and gestational age
- To search for any fetal structural defect
- To check fetal well being
- To help in the performance of invasive therapeutic and diagnostic procedures
Accurate diagnosis of fetal malformation improves patient care by proper counselling and allowing for informed patient and obstetrician decision making
Screening for chromosomal defect
IN FIRST TRIMESTER (11 – 14 weeks) Combined screening by serum markers ( blood test ) and Nuchal translucency ( ultrasonography ) has improved the detection rate up to 90 % with a false positive rate of 5 %.
Nuchal Translucency – is the most important marker for general population screening. Increased nuchal translucency is a marker for structural and chromosomal defect. By using nasal bone, ductus venous Doppler and tricuspid flow the diagnostic accuracy can be further improved.
Second trimester screening – Second trimester screening includes a combination of genetic sonogram and quad test. Quadruple marker serum screening is the most effective form of aneuploidy screening in second trimester. Those patients who have missed first trimester screening can opt for this test.
Prenatal diagnostic procedures
Invasive diagnostic procedures play an important role to obtain genetic, biochemical and physiological information about the fetus.
The three main diagnostic procedures includes
- Amniocentesis
- CVS ( Chorionic villous sampling )
- Cordocentesis ( fetal blood sampling )
Three main diagnostic procedures
Amniocentesis
Under continuous ultrasound guidance 22G spinal needle is introduced inside the uterus, to reach an amniotic fluid pocket devoid of fetal parts and placenta. Around 20 cc of amniotic fluid is aspirated and sent to genetic lab for further investigations
It is the most common invasive procedure performed prenatally. This procedure is ideally performed after 15 weeks of pregnancy to reduce procedure related complications .it is reported that. If performed before 15 weeks (early amniocentesis), the complications like tulips euinovarus, miscarriage and amniotic fluid leakage are increased.
CVS (Chorionic villous sampling )
This procedure is ideally performed after 11 weeks of pregnancy as limb reduction defects are reported in procedure performed too early . In this procedure, 18 G Spinal needle is introduced into the long axis of placenta under USG guidance. A 20 ml syringe is attached to spinal needle after removing the stylet. Negative suction is created and needle is moved up and down within the placenta to aspirate chorionic villi.
The aspirated villi are then transported in media to the genetic lab.
Cordocentesis (fetal blood sampling )
it is also called as percutaneous umbilical (fetal) blood sampling procedure. Usually performed after 18weeks of pregnancy.
20 g spinal needle is inserted transabdominal into umbilical vein and fetal blood is aspirated.
It was initially introduced to diagnose haemoglobinopathies, now a day’s umbilical vein cannulation is usually performed in cases of erythroblastosis fetalis for intrauterine blood transfusion.
Fetal Therapy
A range of fetal surgical and pharmacological interventional procedures continue to develop with improvement into the knowledge, technique and instrumentation.
Fetal pharmacological treatment is successful in cases with congenital adrenal hyperplasia, cardiac arrthymias, thyroid disorders and fetal infections
The expanding list of fetal surgical procedure includes-
- Fetoscopic surgery / interventions in twin to twin transfusion syndrome ,amniotic band syndrome and TRAP.
- Intrauterine radiofrequency ablation in twin reversed arterial perfusion (TRAP )
- Intrauterine shunt procedures to decompress collections in pleural effusion ,CPAM AND bladder outlet obstruction , PUJ obstruction.
- Balloon valvuloplasty in aortic stenosis.
- Open fetal surgery in fetus with sacrococcygeal teratoma , congenital pulmonary airway malformationand meningomyelocele.
- EXIT procedure for management of compromised fetal airway
Our understanding of fetal anatomy, physiology and molecular disorders of fetus have increased with advances in genetics, prenatal diagnosis and ultrasonography .therefore more and more advances in fetal therapy is anticipated.
