Fetal Well-being Scan

Fetal Age, Size, Growth and Weight

The age of the baby is established in early pregnancy. The size of the baby can be compared with the size expected for this stage of pregnancy, giving information about the baby’s growth. An estimate of the weight can be calculated from the measurements.

Recent research has shown that relying on measuring the size of the bump (Symphysis-Fundal Height) is unreliable in detecting small babies who are not growing properly and only picks up 30-50% whereas ultrasound scans will identify about 80-90% of babies with growth retardation. We advise serial growth scans at 24, 28, 32 and 36 weeks for optimal growth surveillance.

The biophysical profile is a measure of the baby’s health and uses ultrasound to examine fetal body movements, breathing movements, tone, amniotic fluid volume and sometimes heart rate variability. This gives an indication of the baby’s general wellbeing and identifies babies who are hypoxic (low on oxygen) who may need to be delivered early.

The purpose of this examination is to assess:

  • Position of the baby
  • Size of the baby
  • Amount of fluid surrounding the baby
  • Placental resistance to blood flow
  • Baby’s current state of health

Most babies are head down towards the end of pregnancy. Occasionally the baby can be in a breech position, where the bottom is closest to the cervix (opening to the uterus).

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