This is the single most important pregnancy scan and also the most challenging to perform. Its main purpose is to confirm that the baby is forming normally. Important anatomical structures such as the spine, brain, heart, kidneys and limbs are examined. Though many abnormalities are reliably detected with ultrasound, others such as some heart defects or brain malformations may either develop at a later stage of pregnancy or be much more difficult to diagnose. Overall, approximately half of serious abnormalities can be expected to be diagnosed with a good 18-20 week scan.
If you have a family history of any form of birth defects, genetic problems or are taking medications it is important to tell the person doing your scan.
It will also look at the placenta. At this stage approximately 5% of placentas will lie over or close to the cervix. Less than 1% will still block a vaginal birth at term but if we find a low placenta at 18-20 week scan we will often recommend checking the position of the placenta in late pregnancy.
Finding a problem with a baby is a very frightening and confronting experience for parents. If this occurs you will be spoken to by one of the doctors in the practice who appreciate that understanding complicated medical concepts can be very difficult immediately after bad news. Often follow-up visits are arranged when partners or other members of the family may wish to attend. Determining the exact nature of an abnormality and what the implications are for the baby is not always straight forward and may involve other tests and referral to other specialists.
Please drink 2 glasses of water in the hour before your scan
Because this is a very detailed scan we cannot always complete it in the booking time allowed and you may be asked to go for a walk and return or rebook for completion views.
If you or your partner have a family history of an abnormality in a newborn baby please mention this at the time of the scan
Please remember that even a normal scan does exclude all abnormalities or causes of developmental delay