How Ultrasound Scans Know So Much About Babies In Utero

Ultrasound scans are an amazing painless way of seeing how your baby doing inside the womb. The technology has so far allowed us to have a glimpse of the womb world—we have been able to find the location of the baby in utero, detect their heartbeat and their gender even before they are born.

You will be able to see your baby via an ultrasound scan by as early as 7 weeks into pregnancy. By that time, you could only notice that little heart beating incessantly. However, detecting the fetus can get challenging sometimes. If nothing shows on the screens, your doctor might advise you to come a week or two later, during which, the amniotic sac or fetus grows as much as is requires to be detected through the scan.


How Does An Ultrasound Scan Work

An ultrasound scan uses high-frequency sound waves unlike any other harmful radiation to detect the fetus. These sound waves are transmitted through the mother’s belly using a device called transducer, which is moved along on the mother’s belly. When these sound waves hit the body tissues and fluids, some of them get reflected back—this is picked up by the device and interpreted in the form of images, which is displayed on the screen.

Here is what all your doctor can determine using an ultrasound scan.


1. Noticing Your Baby’s Heartbeat

The fetal heartbeat can be detected between 6-7 weeks of pregnancy. Seeing your baby’s tiny pulsating heart right on the screen is exciting and overwhelming. By this time, their heartbeat will be between 90-110 beats per minute. If the heartbeat is not picked up by the scan, your doctor will ask you to return for a scan after a week or two.

2. Identifying The Fetal Pole

The fetal pole is basically the fetus itself, which is seen at the periphery as a thick margin of the yolk sac that provides nourishment to your baby in the early days. The yolk sac is also seen by the doctors by 7 weeks of pregnancy. It is alright if the fetal pole is not visible until 9 weeks, you may be asked to come back for a scan later.
Fetal pole is somewhat bean-shaped and the doctor can determine the size of the baby by studying it.


3. Position Of The Baby

The first proper ultrasound scan can also reveal the position of the baby—its exact location in the womb. The patterns of the blood flow seen during the scan can help detect complications like ectopic pregnancy, early in the gestation.

4. The Gender Of The Baby

Another surprise for the parents that only an ultrasound scan can safely predict is the sex of the baby. Between 18 to 22 weeks, one can find the gender of the baby through the scan—though, most people still keep it as a secret to be revealed naturally at birth.


5. To Determine The Due Date

Ultrasound scans also help determine the due date—though, sometimes, the birth day of your baby may not arrive as accurately as predicted.

The delivery date is usually calculated by knowing the first date of your last menstrual cycle. However, if you aren’t aware of the start date of your last period, an ultrasound can help determine the gestational age—it is most effective in the first trimester itself.


The fetal pole size also called the crown-rump length (CRL) is determined and measured using the ultrasound scan through which the due date is estimated using the size of the fetus.

Note that if the heartbeat is not captured in the scan it could indicate that the fetus has not survived or is not developing. There are further tests to determine that before the doctor arrives at a conclusion about the pregnancy.


There are also chances that the checkup was done too early in the pregnancy and the cardiac development hasn’t taken place. Discus with your doctor or take second opinions on it.