Your 20-week ultrasound is the first opportunity for you and the sonographer to see how your baby’s body and organs are developing. If so desired, you will also probably be able to find out your baby’s sex. At the appointment, your sonographer will closely examine your baby’s body systems and organs to see if there are any signs of a problem. Most of the time, the sonographer will be able to tell you that your baby is developing normally. If there are any signs of abnormalities, the sonographer will refer you to a doctor who will take a closer look at any areas of concern and continue to follow up with you for the duration of your pregnancy.
During the 20-week ultrasound, the sonographer uses a wand-like instrument coated with a special gel on the outside of the abdomen to see inside the uterus. Ultrasound images are usually black and white and grainy, but you should still get some exciting glimpses of your developing baby.
Your Baby’s Size
The sonographer will take measurements of several parts of your baby’s body. After measuring the head width and circumference, the abdominal circumference, and the upper leg length of your baby, the sonographer will put these measurements into a mathematical formula to estimate the baby’s size. This will indicate if your baby is normally sized for this stage of your pregnancy.
If the baby is a couple of weeks more or less developed than expected for your assumed conception and due dates and you didn’t have an ultrasound scan during your first trimester, the sonographer may revise your dates. An ultrasound scan in the first trimester will generally indicate the most accurate dates; however, if you didn’t have a first-trimester ultrasound, the 20-week ultrasound can provide some clues. In rare cases, a lag in the baby’s development may indicate a growth issue, but most slight variations in growth and development are normal.
The sonographer will check to see if the placenta looks normal and whether it may be blocking the cervix, or birth canal, which is not unusual in the second trimester. If the placenta is in the way, the doctor will schedule a follow-up later in the pregnancy to see if it has moved away from the cervix. In most cases, the placenta naturally shifts before the third trimester.
The Amniotic Fluid
Your amniotic fluid will be checked to ensure that it is a healthy amount. Too little fluid could be a sign of a growth issue or a renal problem in the baby. The baby will be monitored in this case. Too much fluid could increase the risk of premature labor. It is possible to drain some of the excess fluid through amniocentesis to lower the risk.
There are signs to indicate that the baby may have a higher risk of chromosomal abnormalities such as Down’s Syndrome. The signs themselves are not a cause for alarm, but they may indicate the need for a diagnostic test, and they will continue to be monitored during the pregnancy.