Early Scan - 6 to 11 weeks
An early pregnancy scan is usually performed to check the expected date of delivery, the viability of the pregnancy and the number of fetuses. It is usually performed transvaginally, as this gives the best possible resolution and the most information at this stage. By getting closer to the fetus, we are able to use a much higher resolution transducer, and therefore obtain clearer images. The transducer is introduced into the vagina and the sonographer or doctor will position it so the best possible images of the fetus are obtained. These internal scans will not harm you or the baby and are universally standard practise. There is no need to fill your bladder or undertake any other preparation. You will be informed of what is seen and staff will ensure you understand what is happening. If everything is going well with the pregnancy, you will be given some images to take home.
Early ultrasound scans are usually performed when there is a question as to the date of the last menstrual period. As the fetuses are all very much the same size at this gestation, it is the most accurate time to ascertain the due date of the pregnancy. The fetal heart can be seen from six to seven weeks, therefore viability of the pregnancy can be confirmed.
IVF pregnancies routinely undergo an early pregnancy scan to determine the number of fetuses and viability.
Other common reasons for scanning at this early stage are previous history of miscarriage, a previous ectopic pregnancy or if the patient has had bleeding during the pregnancy. In about half of suspected ectopic pregnancy cases, a mass can be seen on the scan. In the other half, the ectopic may be suspected if no fetal pole can be seen in the uterus but the blood test indicates at least a 6 week pregnancy.
At 5 weeks from the first day of your last menstrual period only a gestational sac will be visible. After this, a yolk sac will be visible, then a small fetus. The size of the fetus has to be at least 2mm to see a heart beat . Ideally, we try to undertake this scan from 6.5 weeks gestation. Sometimes the pregnancy is found to be only 5 weeks gestation and at this stage only a gestational sac will be seen. In these cases we will need to rescan you a few days later to confirm that the fetus is developing.