Ultrasound has been used for more than 30 years and
is not known to cause any harm to pregnant women or
her baby. That said, ultrasound should not be routinely
used unless your doctor has a specific medical reason
for doing so.
How accurate is
ultrasound in dating a pregnancy?
Ultrasound is extremely accurate when used during
the first trimester. Measuring the baby's crown to
rump length at this stage can pinpoint a baby's gestational
age within 3-5 days while similar measurements taken
during the other two trimesters take relatively longer.
Therefore the first trimester is the preferred time
to date a pregnancy.
What are the other
reasons for performing a first trimester ultrasound?
• Your doctor may order a first trimester ultrasound
• Pinpoint the location of the gestational sac
(the developing fetus is contained within this sac),
something that can be useful in
• diagnosing an ectopic pregnancy.
• Look for evidence of an embryo
• Check for a fetal heartbeat
• Find out if you are carrying more than one
• Examine the uterus for structural abnormalities
or other problems that could pose problems during