Why have an ultrasound at 20 weeks?

The 20 week ultrasound is to check organ development in detail. Some organs such as the heart, lips and palate, lower spine and digits are too small to check at 12 – 13 weeks. A detailed examination of all structures visible on ultrasound will be performed. In almost all cases reassurance will be given that the anatomy as seen on ultrasound is developing normally.

What can you see on the scan?

Very small abnormalities such a hole in the heart or cleft lip may not be seen even with the best equipment and skill. Some abnormalities may develop later in pregnancy conditions such as autism and cerebral palsy cannot be diagnosed using ultrasound as there is no visible abnormality. If a 12 – 13 week ultrasound has not been performed the due date can be worked out at this examination. 

Can I do downs syndrome testing at 20 weeks?

Down Syndrome Screening cannot be performed using ultrasound at 20 weeks. Please see CVS and amniocentesis for further testing options.

Can you see the placenta's position at 20 weeks?

The position of the placenta is checked. 1 in 20 placentas are low at 20 weeks but most move away as the pregnancy grows. 1 in 100 placentas are low at 32 weeks. If the placenta is low at 20 weeks a check is usually done at 32 weeks 

Will I be able to know the sex of my baby?

The 20 week ultrasound is very accurate in determining the sex of the baby. It is correct 99% of the time. At the 12 – 13 week ultrasound it is sometimes possible to sex the baby but not as accurately. In 10% of cases it is not possible to sex the baby and where sexing is done it is wrong 10% of the time. 

How Long will the scan take?

The 20 week scan typically takes 30 minutes to complete. Occasionally we can’t see/scan everything because of your baby’s position or the position of your placenta. Your own BMI also affects how well we can see your baby on ultrasound. 

How do I prepare for the scan?

There is no preparation for a 20 week scan, although it is always helpful to have a partially filled bladder.