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- Position of pregnancy (i.e. inside the uterus)
- Number of babies
- Presence of heart motion
- Age of pregnancy (from the first day of menstrual period)
The ultrasound appearance will depend on the age of the pregnancy. At 5 weeks gestation only a gestation sack will be seen. After this a yolk sac will be visible, then a small fetus.
The size of the fetus has to be over 4mm to see a heart beat. A viable fetus can be seen before the heart has begun to beat.
Dating the pregnancy by measuring from the head to the bottom (crown-rump length) is very accurate (+ /- 3 days).
Most miscarriages are due to chromosomal abnormalities. Occasionally a pregnancy may occur outside of the uterus, which is know as an ectopic pregnancy.
An assessment of the baby's structure is difficult before 12 weeks, when a Nuchal Translucency scan can be performed.
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Fetus in profile |
Twins Sometimes more than one baby will be seen (twins or triplets) or the pregnancy may not be viable (miscarriage). |
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