When to have dating ultrasound
The test does come with risks—the earlier the amniocentesis takes place, the higher the risk of miscarriage. Chorionic Villus Sampling (CVS) as an alternative to amniocentesis because it can be done earlier (between weeks 10 and 12).
Like the amniocentesis, the test takes about half an hour and may be uncomfortable.
• The VDRL: Pregnant women require a syphilis test because the disease can cause neurological damage to the baby or even stillbirth.
• Genetic disorders: If tests haven’t already been done, your doctor or midwife may request tests. If a test turns out positive, treatment can dramatically reduce the baby’s risk of acquiring the disease.
(Read about those tests below.) The ultrasound technician will also measure the length of the fetus to give caregivers a more accurate estimation of your due date.
If the test indicates a high likelihood, caregivers will recommend amniocentesis or CVS (Chorionic Villus Sampling), which are more invasive tests, but will give you accurate diagnoses.
Specifically, caregivers test for abnormal levels of h CG (human chorionic gonadotrophin) and PAPP-A (pregnancy associated plasma protein).
The test can also tell you the sex of your baby, the Rh factor and the maturity of his/her lungs (which is useful if you show signs or have a history of premature delivery).