The main purposes of this ultrasound examination are to confirm the pregnancy duration, to screen for Down syndrome (and other chromosomal syndromes) and to evaluate the baby’s development. It can be done from 11 weeks 4 days to 13 weeks 6 days. It is also a useful time to screen for pre-eclampsia.
The main purpose of this ultrasound examination is to to evaluate the baby’s structural development. It can be done from 19 to 22 weeks. It is also a useful time to screen for preterm labour.
This ultrasound examination is usually done after 26 weeks. The size of the baby is measured, and Doppler ultrasound is used to evaluate blood flow in the umbilical cord and different blood vessels in the baby.
By means of a blood test which is done on the pregnant woman, Down syndrome and other common chromosomal abnormalities (trisomy 13, trisomy 18 and X and Y-abnormalities) can be diagnosed with a high degree of accuracy. Still expensive, and not quite as accurate as amniocentesis or chorionic villus sampling, but definitely a viable option.
Other diagnostic tests
A fetal MRI might be requested for further information. This is a link to information from the Texas Children’s Hospital, but applicable to our local circumstances.
One of the biggest drawbacks of fetal MRI is artefacts caused by the baby’s movements. You might receive a tablet that makes both you and the baby drowsy (so, please don’t drive yourself afterwards!) It is also good not to have a large meal or sugary drinks less than two hours beforehand.
Invasive diagnostic procedures
With an amniocentesis, a specimen of amniotic fluid is obtained by placing a needle through the abdominal wall into the womb’s cavity. The fluid and cells in the amniotic fluid originate from the baby, and can be used to diagnose specific conditions of the baby.
With a chorionic villus sample (CVS) a sample of the chorionic villus cells which form the placenta is obtained by placing a needle through the abdominal wall into the placenta. These cells originate from the baby, and can be used to diagnose specific conditions of the baby.
With a cordocentesis, a blood sample the unborn baby is obtained by placing a thin needle through the abdominal wall into the umbilical cord. The blood in the umbilical cord originates from the baby, and can be used to diagnose specific conditions of the baby.
If an unborn baby is severely anaemic, blood is given to the baby through a thin needle which is placed through the abdominal wall into the umbilical cord or baby’s body cavity.
Twin-to-twin transfusion syndrome (TTTS) is a complication of identical twins, where one twin produces too much amniotic fluid, and the other is “stuck” because of a lack of amniotic fluid. This can be treated by lasering vessels on the surface of the placenta by means of a fetoscope.