Our Services Pre-Natal Diagnosis Early Fetal Morphology Scan

First trimester fetal morphology scan aims to carry out an early assessment of fetal structures. In case the baby has some structural defect(s), the parents may know about it earlier. The early identification of abnormalities of the baby allows prenatal diagnosis for chromosomal or genetic cause and early counseling on the prognosis of the condition. For certain major congenital defects, the parents might have the option of an early termination of the pregnancy.

How is first trimester morphology scan different from the ordinary antenatal ultrasound?
During an ordinary antenatal ultrasound, the fetal heart pulsation, fetal size, amniotic fluid volume around the fetus and the placental site are usually assessed. For a first trimester fetal morphology scan, in addition to the above parameters, commonly assessed structures include: cranium, falx cerebri, choroid plexus, orbits, facial profile, nasal bone, mandible, nuchal translucency, spine, 4 chamber heart, fetal heart rhythm, lung, stomach, umbilical cord insertion, long bones of limbs, hands and feet orientation.

When is the best timing for first trimester fetal morphology scan?
A first trimester fetal morphology scan is usually performed during 11-14 weeks of gestation. The more advanced the gestational age, the easier the fetal parts can be assessed.

What are the limitations of first trimester morphology scan?
First trimester fetal morphology scan can pick up about half of the major fetal structural abnormalities. As the fetal size is small at this stage and the fetus will continue to develop, some major malformations may not be obvious at this stage or may develop in later pregnancy. Hence, not all major fetal abnormalities can be detected at this stage, even with the appropriate ultrasound equipment and in the most experienced hands. Sometimes, structural abnormalities might be suspected but not confirmed yet on a first trimester morphology scan, in which case, a follow-up morphology scan is needed a few weeks later.

The accuracy of a morphology scan in general depends on a number of factors, including the severity and nature of the abnormality, whether the fetal position is optimal for scanning, women’s factors such as whether the tummy is thick or there is surgical scar, the quality of the ultrasound machine and whether the medical personnel are experienced in or have received adequate training in this practice.

Can first trimester morphology scan replace second trimester morphology scan or Down syndrome screening?
First trimester morphology scan is regarded as an extra scan performed in first trimester and is not a substitute for Down’s screening test or the second trimester morphology scan (usually performed at 20-22 weeks of gestation). Some gross malformations may develop later in pregnancy and may not be detected in the first trimester. We advise you to have a Down’s screening test and the routine second trimester morphology scan even though the first trimester morphology scan is normal.