This is a systematic study of your baby from head to toe. It is similar to an ultrasound scan of an adult only it involves a head to toe study.
Most babies are born normal. 4% of babies are born with major structural defect. The risk is higher with advancing age, certain medical conditions, certain drugs for medical conditions, alcohol consumption and familial transmitted conditions.
A detailed structural scan performed between 18 and 22 weeks will identify most of the major problems.
A report should be issued and should be kept as a medical record of your baby. Not all babies scanned normal at this stage are actually born normal. Some conditions only manifest later in pregnancy. Infections are also known to cause abnormalities in organs already confirmed as normal. Usually a second look at 30-32 nd week of pregnancy will settle this.
WHAT IS CHECKED FOR IN THE BABY DURING THE DETAILED SCAN?
The following structures should be confirmed to be present and normal in appearance at this scan visit:
Cranium: skull shape and calcification. Presence of skull defects. Brain within the skull. facial profile, lip and nose, eyes.
Brain structures: midline falx, cavum spetum pellucidi, thalami, cerebral peduncles, third and fourth ventricles, cerebellum, lateral ventricles, cisternal magna, nuchal fold, corpus collasum, normal grey and white matter.
Chest: ribs, spine, lungs, diaphragm, trachea, esophagus, and heart.
Heart: normal position, size. 4 chambres, septum, LVOT, RVOT, pulmonary and its branches, aortic arch, ductal arch, valves, pulmonary veins
Abdomen: stomach, kidneys, bladder, cord insertion, bowels,
Spine: sagittal, coronal and transverse views of entire vertebral column
Upper and lower limbs: all 12 long bones of arms, forearms, thigh and legs, hands and feet
Placenta: cord insertion, position and liquor volume
HOW LONG WILL THIS TAKE?
This usually requires 20 minutes of your time. Sometimes it can take longer if a certain defect is detected or if the baby is lying in certain position that make scanning difficult.
You can make the following conclusions if the 2nd trimester detailed scan was normal:
1. 80% of major defects are excluded
2. 80% of major heart defects are excluded
3. The age related Down syndrome risk is reduced by 50%. The scan is not conclusive for absence of Down Syndrome. 30% of Down Syndrome babies are normal on ultrasound.
4. There was no problem with biometry (measurements to ensure growth is appropriate).
5. The placenta looks normal and in the correct location with normal cord insertion
6. The amniotic fluid level is normal
7. The uterus is normal.
8. If you opted for screening for preterm birth - the length of the cervix is normal.
9. This is a structural scan and not a functional study - eg autism, palsy, other non-structural disorders cannot be assessed by ultrasound examinations.