At Women Fertility & Fetal Centre, we are committed to providing our female patients with a safe pregnancy and a smooth delivery of a healthy baby.
The first ultrasound that will demonstrate the presence or absence of a viable fetus, a fetal viability scan is particularly helpful for women with previous pregnancy losses or who are undergoing assisted reproduction, as their anxiety levels are usually higher.
The earliest one can confidently see a fetal pole and the presence of fetal heart pulsations is from 6 weeks onwards. The CRL (crown rump length) of a fetus at 6 weeks is approximately 3 to 5 mm. For better accuracy, the scan is performed transvaginally.
A fetal viability scan helps to exclude ectopic pregnancy by confirming the presence of an intrauterine pregnancy, as well as the absence of any abnormality outside of the uterus. It also helps to accurately date the pregnancy if it is performed prior to 10 weeks gestation. In case of multiple pregnancies, it is essential in the determining of the type of twins.
An NT scan is a special ultrasound scan that is used to check the thickness of the nuchal translucency—the fluid present at the back of a baby’s neck—and the presence of the nasal bone. An abnormal amount of the nuchal fluid, together with the absence of the nasal bone, indicate a higher risk of a chromosomal disorder such as Trisomy 21 or Down’s Syndrome.
This scan is typically done during the first trimester, between 11 to 14 weeks of pregnancy. It has an accuracy of around 75%.
A combination of the NT scan and a maternal blood test that measures the levels of pregnancy-associated plasma protein-A (PAPP-A) and human chorionic gonadotropin (hCG).
OSCAR is performed during 11-14 weeks of pregnancy. When combined with a NT scan, the accuracy rate of detecting Trisomy 21 increases to 85-90%.
With 99% accuracy for Trisomy 21, NIPT evaluates the free fetal DNA, which is present in the mother’s blood during pregnancy, to check for the presence of variants in the amount of free Fetal DNA. This would give an indication of any risk of a genetic disorder.
This screening test—which can be performed from as early as 9 to 10 weeks of gestation—is used to assess whether further diagnostic tests are needed. This is the most sensitive test to date for the common trisomies and can be tested on both low- and high-risk patients.
This technique involves taking a sample of the chorionic villi from the placenta through the abdominal wall. Chorionic villi refer to finger-like projections within the placenta that contain the baby’s genetic makeup.
A CVS test is typically done during 11 to 14 weeks gestation, and is usually ordered to further confirm the high-risk results from a screening test, or exclude a chromosomal problem in the presence of a structural fetal abnormality.
An amniocentesis involves taking a sample of the amniotic fluid—the liquid that surrounds the fetus in the womb—via an ultrasound-guided needle. It is best performed at 16 weeks of pregnancy. Amniotic fluid contains fetal cells from which the genetic testing is performed.
This removes the risk of placental mosaicism as the placenta occasionally has cells which are different from the fetus.
The definitive ultrasound scan which is usually performed anywhere between 18 to 22 weeks gestation. A fetal anomaly screening scan aims to help detect any major fetal structural abnormalities, as well as demonstrate the location of the placenta and determine the uterine blood flow during mid-pregnancy.
Abnormalities which can be detected with a high degree of accuracy include: anencephaly, bilateral renal agenesis, cleft lip, diaphragmatic hernia, Edward’s syndrome (T18), exomphalos, gastroschisis, lethal skeletal dysplasia, open spina bifida, Patau’s syndrome (T13) and serious cardiac abnormalities.
An ultrasound assessment of the cervical length can help determine whether the expectant mother is at risk of preterm labour. It is recommended for this test to be done before the second trimester for the sake of early intervention and treatment if necessary.
Conducted anytime between 24 to 41 weeks of pregnancy, this diagnostic scan monitors the baby’s growth and development including placental condition, observe fetal movements and determine amniotic fluid volume. This may be done alongside a Doppler ultrasound test to measure blood flow from the placenta to the baby, for a better idea of the baby’s functional status.
When the mother goes into labour, ultrasound scans can be used to confirm the lie of the baby to assist the management of the labour. For example, for Caesarean section, a transverse lie is best turned to a breech presentation for ease of delivery.
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