During the 13th week ultrasound, the fetus's eyes are distinguishable, and its ankles and wrists are formed, according to WebMD. The baby's head still looks disproportionately large compared to the rest of the body but is typically more proportionate than in previous scans.Continue Reading
One objective of an ultrasound scan at this stage is to attempt an early determination of the baby's gender. It is possible to distinguish the baby's gender as early as 11 to 12 weeks, according to Dr. Joseph Woo, though it is difficult to be certain before 20 weeks.
By measuring the size of the baby during this scan, doctors more accurately estimate the age of the baby and use this information to estimate the due date. The nuchal fold screening ultrasound scan must take place around this time. This scan helps determine the risk of genetic problems, such as Downs Syndrome, and monitors the baby's development, according to BabyCenter.
In the case of multiple pregnancies, nuchal ultrasound scans around week 13 can detect potential problems, according to the Fetal Medicine Centre. One such problem detected by these scans is the babies sharing the same placenta. Early detection of these problems helps doctors determine how best to monitor the pregnancy.Learn more about Diagnostics & Imaging