Anomaly scan

Prior to 18 weeks' gestation, the fetal organs may be of insufficient size and development to allow for ultrasound evaluation.

Scans performed beyond 22 weeks' gestation may limit the ability to seek pregnancy termination, depending on local legislation.

These markers are often not clinically significant and do not cause adverse pregnancy outcomes, but used in order to decide whether additional tests, which will be more accurate, are needed.

However, performing an ultrasound for the sole purpose of determining fetal sex without a medical indication is not recommended.

These factors include the severity of the anomaly, the background risk of the study population, gestational age at time of scan, the expertise of the ultrasound technician and interpreting obstetrician, and maternal obesity.

Anatomy scan image of a human placenta and umbilical cord (colour Doppler rendering) showing central placement of the cord in the placenta and three vessels in the cord, which is the normal physiology.
Anatomy scan of the fetal head at 20 weeks of pregnancy in a fetus affected by spina bifida . In the axial scan the characteristic lemon sign and banana sign are seen.
Anatomy scan with power bi-directional colour Doppler of both fetal kidneys at 18 weeks of pregnancy to detect renal agenesis . The videoclip shows a frontal scan with normal renal blood perfusion during fetal breathing movements.