Fetal health screening FAQs

About two to five percent of babies are both with some type of birth defect. While small, it’s a scary percentage for expecting mothers. Dr. Tony Tan, a specialist in Obstetrics and Gynaecology, Raffles Women’s Centre credits the defects to something unfortunately out of anyone’s control.

“[They] may be due to chromosomal abnormality, genetic disease or structural abnormality in the baby,” he says.

For this reason, medical experts say it’s important for women of all ages, not just those aged 35 and above, to consider fetal health screening. Many abnormalities are random events and may not be easily identified by factors such as age of family history, but they can be picked up by pre-screenings.

Dr. Chow Kah Kiong, specialist in Obstetrics and Gynaecology, Raffles Women’s centre, recommends all pregnant mothers to go for foetal screening, of which “the most usual one is a routine blood test” and “the next almost universal test is an early ultrasonography on the foetus.”

Dr. Tan sheds light on different types of fetal health screening that can be conducted during the first, second and third trimesters of your pregnancy.

First trimester

The First Trimester Screening is conducted between the 11th and 13th week of your pregnancy. It combines historical data, high resolution Ultrasound scans with the mother’s blood. This screening is safe and poses no risk of miscarriage or other complications.

This test has been improved over the years to screen for common chromosomal abnormalities such as Down syndrome, early structural abnormalities, and the risk of pre-eclampsia (a condition which manifests as high blood pressure with proteins in the urine during pregnancy that requires delivery before 34 weeks). In fact, the First Trimester Screening is recognised as the best screening test for Down syndrome.

In addition to screening for Down syndrome, this test allows the identification of those at high risk for severe pre-eclampsia to benefit from the use of medications such as calcium supplementation and low dose aspirin early in pregnancy. This can reduce the risk of pre-eclampsia.

Second trimester

The foetus is next screened around 20 weeks for common structural abnormalities that can be detected by Ultrasound, placental localisation and cervical length. This screening allows the identification of structural abnormalities that need to be treated during pregnancy or soon after delivery. 

Possible structural abnormalities:

If the placenta was low-lying

The obstetrician would need to take note of symptoms like vagina bleeding and check the location of the placenta in the third trimester to determine whether a Caesarean section is required for delivery.

If the cervix is short

A short cervix at 20 weeks increases the risk of premature delivery before 33 weeks. The doctor may treat you with progesterone to reduce the risk of premature delivery.

Third trimester

The foetus can be screened for growth disorders. In five percent of cases, the fetus is growing below the normal range. Such fetuses should be monitored closely so as to determine the best time for delivery.

A 3D or 4D scan can be conducted as this time, purely for bonding between parents and their growing baby. Unlike traditional 2D ultrasound scans, 3D scans send sound waves at different angles. The returning echoes are processed and reconstructed, resulting in a 3D image of the foetus’s surface or internal organs. 4D ultrasounds string together frames of 3D ultrasounds to see movement.

Dr. Tony Tan and Dr. Chow Kah Kiong are specialists in Obstetrics and Gynaecology from Raffles Women’s Centre in Raffles Hospital, a tertiary care hospital and the flagship of the Raffles Medical Group, a leading private healthcare provider in Singapore and South East Asia.