Obstetric Ultrasound
An obstetric ultrasound uses sound waves to show your baby in the womb. It confirms the pregnancy and its location, checks the baby's heartbeat, dates the pregnancy accurately, detects twins, examines the baby's anatomy and growth, and assesses the placenta and the amount of amniotic fluid.
At YGOPH, obstetric ultrasound is performed as part of antenatal care and at any time in an emergency. The World Health Organization recommends at least one scan before 24 weeks; many women have one scan in each trimester, and women with high-risk pregnancies are followed more closely, sometimes with Doppler studies of blood flow.
What happens during a pregnancy scan?
You lie on your back and gel is applied to your abdomen. The sonographer moves a probe over your skin and watches the images on a screen, taking measurements of the baby. In early pregnancy, a transvaginal probe may give clearer images; it is safe for the pregnancy and only used with your consent. Most scans take 15 to 30 minutes, and you are welcome to ask questions during the examination.
- First trimester: confirming the pregnancy, its date and the number of babies
- Around 20–24 weeks: checking the baby's anatomy and the placenta
- Third trimester: growth, position and amniotic fluid
- Bleeding, pain or reduced baby movements at any stage
- High blood pressure, diabetes, twins or other high-risk situations
Good to know
The main scans in pregnancy
A dating scan in the first trimester gives the most accurate due date. The anatomy (morphology) scan, usually between 20 and 24 weeks, examines the baby's organs and can detect some malformations. A third-trimester scan checks growth, the baby's position and the placenta, and helps plan the birth.
Doppler in high-risk pregnancies
When the baby is small, or the mother has pre-eclampsia or another complication, Doppler ultrasound measures blood flow in the umbilical cord and the baby's vessels. It helps the obstetrician decide whether the baby can safely continue to grow in the womb or should be delivered earlier.
What ultrasound cannot do
Ultrasound is very useful but not perfect. Some abnormalities cannot be seen, especially if the baby's position is difficult. A normal scan is reassuring but cannot guarantee that the baby is completely healthy. Scans are performed for medical reasons; seeing the baby's sex is not their purpose and is not always possible.