A routine imaging method that uses sound waves to evaluate the baby's development, well-being and the placenta throughout pregnancy. It is safe for both mother and baby.
Indication
- Confirmation of pregnancy and assessment of the location of the gestational sac
- First-trimester (11-14 weeks) nuchal translucency and early anomaly screening
- Second-trimester (18-22 weeks) detailed fetal anomaly (level II) screening
- Third-trimester follow-up of growth, placenta and amniotic fluid
- Suspicion of multiple pregnancy, placenta previa or intrauterine growth restriction
- Evaluation in cases of vaginal bleeding or suspected pregnancy complications
- Doppler monitoring of blood flow in high-risk pregnancies
Preparation
- In early pregnancy, a full bladder may be helpful for transabdominal examination
- In later weeks, a full bladder is not necessary
- Fasting is not required
- Bringing previous examination and test results is recommended
How it's performed
- The patient is placed supine on the examination table
- Ultrasound gel is applied to the abdomen
- The probe is moved over the abdomen and the baby, placenta and amniotic fluid are examined
- When needed in early pregnancy, a transvaginal probe may be used for detailed imaging
- The baby's head, spine, heart, abdomen and extremities are systematically evaluated
- Doppler is used when needed to measure uterine artery and umbilical cord blood flow
Post-procedure
- Findings are recorded in the prenatal follow-up card and patient file
- Examinations are repeated at recommended routine intervals (generally at least once in each of the first, second and third trimesters)
- Frequency may be increased depending on risk status
- Referral to a tertiary center or perinatology may be recommended in case of suspected anomaly
- Return to daily life is immediate after the procedure
Risks
- No known harmful effects of obstetric ultrasound at diagnostic doses have been reported
- Image quality may be limited by maternal body habitus, fetal position or amount of amniotic fluid
- Some structural anomalies may become apparent only in later weeks or after birth
- Screening tests may produce false positive or false negative results
FAQ
Does obstetric ultrasound harm the baby?
There is no evidence that obstetric ultrasound at diagnostic levels harms the mother or baby. Even so, unnecessary repetitions are best avoided.
How many ultrasounds are performed during pregnancy?
Generally at least four scans are performed: pregnancy confirmation in the first trimester, nuchal translucency at 11-14 weeks, detailed anomaly screening at 18-22 weeks, and growth screening in the third trimester. The number may increase in high-risk pregnancies.
At what week can the baby's sex be determined?
Sex can usually be assessed by ultrasound starting from the 16th week; clarity may vary depending on the baby's position.
What is the difference between detailed ultrasound and routine ultrasound?
Detailed (level II) ultrasound is a comprehensive scan performed at 18-22 weeks in which organ systems are examined one by one. Routine ultrasounds are shorter follow-up scans for basic assessment.
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