Second Trimester Scan

Also known as anomaly scan, most women are offered second trimester scan between weeks 18 - 22 to check on the baby's development. An ultrasound scan is not routine and families shouldn't bank on them alone to provide precise results. Nevertheless an ultrasound scan offers reassurance that the baby is developing well so most families opt for it. Second trimester scan is detailed and the whole scan can last for nearly half an hour.

What can a Second Trimester Ultrasound Detect?

• A scan at this point can see the size and shape of organs like the uterus and ovaries.
• The position of the placenta, the quantity of amniotic fluid and the umbilical cord can be viewed on the monitor. The placenta is located on the inner walls of the uterus - sometimes it can by lying close to the cervix (low-lying), or covering the cervix (placenta previa). The placenta usually shifts position in the third trimester.
• Ultrasound also shows fetal movement. Because of your baby's size and the level of fluid, you will be amazed at how much your baby is moving without you even knowing it.
• The sonographer will measure your baby's head circumference (HC) and diameter (biparietal diameter or BPD), the abdominal circumference (AC) and femur or thigh bone (FL) to make sure your baby is growing normally and the size correlates with the date given at your dating scan.
• The anatomy of your fetus can be seen from about weeks 18. A level one scan is basic allowing the technician to view your baby's heart, brain, spine, bowel and limbs, to detect any abnormalities. If problems such as neural tube defects, major kidney problems, major limb abnormalities and defects of the abdominal wall exist, they can all be detected. Other conditions, such as congenital heart problems and hydrocephalus (excess fluid on the brain) may also be diagnosed at this stage. If a problem is identified at this level, a level two ultrasound which is more comprehensive will be recommended where a specialist will perform the scan using high quality equipment to confirm if the anomaly does exist.
• Your baby's sex can be determined after weeks 16 via a scan. If you do not wish to know do inform the technician ahead of time. Gender of the baby is only possible if the fetus is positioned in a favorable way; the genitals will be hidden if baby's position is unfavorable.

Tit - bit

• At your doctor's office your ultrasound scans are referred to what is known as standard ultrasounds or 2D sonography. 3D scans sometimes called 4D allows a three dimensional view of the baby which allows for amazing detailed visualizations of the baby. Medical experts are of the view that 3D scans should be limited to the medical confines since it is sometimes possible to detect something that is not entirely normal without understanding its implication. Therefore 3D scans are used when routine ultrasound calls for it to better view a problem in three-dimension.
• Fetal echocardiogram may be performed to the anatomy of the fetal heart in greater detail if a heart problem is suspected. It is not performed before the second trimester. It is usually recommended in cases where the incidence of heart problem is higher e.g. if the heart anatomy didn’t look normal during the routine ultrasound scan.

Final Word

As mentioned despite all the measuring during the lengthy scan, second trimester ultrasound may provide key information but you need to understand that a basic ultrasound alone is not enough to determine if there is a chromosomal or other abnormality invisible to the eye. A normal ultrasound doesn't guarantee that the baby is healthy since many problems cannot be seen. Similarly in abnormal findings the babies turn out to be fine.