What you Need to Know About Pregnancy Ultrasounds
Ultrasounds are performed during pregnancy generally at key stages of a baby’s development. The first scan will be at your first visit with your Obstetrician in their rooms when the baby is between 7 – 10 weeks gestation. This scan is usually to help your obstetrician confirm your due dates for delivery, how many babies are present and ascertain if the pregnancy is viable.
Miscarriages can occur in the very early stages of pregnancy and whilst a blood test will still detect the pregnancy hormone a scan will allow your obstetric specialist to ensure it is still viable.
The ultrasound machine
In my practice I have two ultrasound machines both of which provide very clear and detailed imager but at the 12 week mark you will need to have a detailed ultrasound performed at specialist Ultrasonographer at a women’s ultrasound clinic. The ultrasound machines are very large and highly complex and enable imagery of all organs including blood flow through the vessels in the heart. This is where many, but not all abnormalities are detected. The ultrasound waves are not harmful to the baby or mother and are well proven in research.
Second trimester ultrasound scans
A detailed ultrasound examination of your baby is again performed at 20 weeks gestation. The baby is larger, and a more significant examination can be made. Having this scan performed at an expert obstetric and gynaecologic ultrasound centre is important to get the most accurate assessment of your baby. They are able to detect a higher proportion of problems in the baby if they exist. The baby’s gender can also be confirmed at this ultrasound.
Having an ultrasound at routine visits in my rooms usually includes assessment of size and position of the baby, activity and fluid volume around the baby and position of the placenta. The Midwives in my rooms are trained to perform these ultrasounds.
Is a third trimester ultrasound necessary?
Sometimes a 34-week ultrasound at an expert centre may be required to assess ongoing issues in your pregnancy. Ultrasound in late pregnancy is reasonably accurate at assessing size for small babies but is not good at predicting size for large babies. An experienced Obstetrician, feeling the baby through the mother’s stomach is more accurate for determining the size of big babies.
Less common is the need for extra ultrasounds in the 16-24 week period for assessment of potential cervical incompetence in high risk women. At these ultrasounds, an internal probe is required to measure cervical length to assess risk.
There are many issues during pregnancy and with your baby where ultrasound may be required, but the results are not central to the diagnosis or management. Conditions such as pre-eclampsia and diabetes may involve an extra ultrasound assessment during the pregnancy. Ultrasound is another part of the overall assessment and care of you and your baby during pregnancy and childbirth.