First Trimester Ultrasound
Confirms that the fetus is alive.
Diagnoses multiple pregnancy if no earlier scan was performed.
Confirms your due date if no earlier scan was performed.
Assesses fetal growth by measuring the fetal head, abdomen and femur.
Assesses the fetal anatomy. This involves a detailed early ultrasound examination of the fetal head, brain, face, heart, stomach, lungs, abdominal wall, kidneys, bladder, spine, arms, legs, hands, and feet.
Assesses the amniotic fluid volume.
Assesses the length of the cervix.
Assesses the mothers ovaries for cysts.
Assesses the uterus for lesions such as fibroids.
Key Information
Most pregnant women will be offered a routine first trimester ultrasound examination to assess the early fetal anatomy. It is usually performed between 12 and 14 weeks gestation, and ideally at 13 weeks. The ultrasound is usually performed transabdominally. Occasionally you may be advised to have a transvaginal ultrasound to achieve better views of your unborn baby. A full bladder is not required.
This examination has the ability to detect a large number of major fetal malformations. However it is important to be aware that even with the best ultrasound equipment not all abnormalities can be seen in the first trimester ultrasound. The majority of major malformations may be detected at the subsequent mid trimester fetal anatomy ultrasound performed at 20 weeks (for further information please follow link to “Routine 20 week ultrasound”)
Sometimes abnormalities can be missed because suboptimal views are obtained. This can be due to difficult fetal position or the patient's weight. In these situations a transvaginal ultrasound may be advised by the doctor performing the scan. If the views remain suboptimal, a repeat ultrasound may be recommended (usually between 15 to 17 weeks gestation) when the fetus is bigger and/or in a different, hopefully more favourable position.
Other times abnormalities may be missed despite good views. This may happen with conditions where the abnormality only becomes evident in later pregnancy or where there are in fact no structural changes in the fetus.