This is a scan usually carried out trans-abdominally at 6 weeks to 10 weeks of pregnancy. The scan can determine the number of fetuses present and whether the pregnancy is progressing normally inside the uterus. It is useful for women who are experiencing pain or bleeding in the pregnancy and those who have had previous miscarriages or ectopic pregnancies. The figure shows a normal pregnancy at 7 weeks of gestation.
1ST TRIMESTER SCANS WILL BE DONE TO:
- Confirm a normal intrauterine pregnancy
- Exclude extra-uterine pregnancy or miscarriage
- Determine the fetal age by measuring the length of the embryo (this will establish the dating of the pregnancy)
- Determine the baby’s heart rate
- Look for multiple pregnancies (twins, triplets, etc.)
- Identify problems of the placenta, uterus, cervix, and ovaries
HOW ACCURATE IS PREGNANCY DATING?
A measurement of the length of the embryo at 7-11 weeks’ gestation is accurate to within about 3 days. Beyond this time the accuracy reduces due to flexion (bending) of the fetus and individual’s growth variance.