I compared my baby weight estimate from ultrasound scan measurements at the last antenatal visit for patients over a 3-month period with actual birth weights.
My scan estimates of weight averaged only 8.14% variation from actual birth weights.
In 89% of cases my scan estimate of baby weight was with 15% of birth weight. in only 3 cases was the variation more than 500gms.
The ultrasound scan weight estimate is derived by using the biparietal diameter (width) of the baby’s head, the head circumference, the abdominal circumference and the length of the femur bone of the lower limb.
My accuracy compares favourably with published data and with results of specialist pregnancy ultrasound units to which I refer patients.
I tell patients all the time I don’t pretend to be an ultrasound scanning expert. I am self-taught. As is the case for most obstetricians, I do not have a certification in pregnancy ultrasound scanning.
All my patients are referred to a specialist pregnancy ultrasound unit for a detailed foetal morphology / anatomy ultrasound scan at 20 weeks. They are also referred at other times in accord with need (e.g. early foetal anatomy scan, cervix check, baby suspected as being too small or too large, checking baby’s wellbeing, etc.).
As well, I did not miss a major foetal anomaly. There was only one – a baby with anencephaly (baby is without parts of the brain and skull). I made this diagnosis at 15 weeks gestation and had the diagnosis confirmed at a specialist pregnancy ultrasound unit.
