08/29/2026
📏📐 Centiles and Fetal Measurements By Jess Rawlinson | Midwife | Student Midwife Studygram 📐📏
📏 Understanding Fetal Centiles 🤰🏼
If a baby is measuring on the 10th, 50th or 95th centile, what does that actually mean?
Centiles help us understand how a baby’s measurements compare with those of other babies at the same gestational age.
For example:
✨ 50th centile means around 50% of babies would be expected to have a smaller measurement and 50% a larger measurement.
✨ 10th centile means around 10% would have a smaller measurement and 90% a larger measurement.
✨ 95th centile means around 95% would have a smaller measurement and 5% a larger measurement.
During a growth scan, you may see several measurements plotted:
🧠 HC = Head Circumference
🤰🏽 AC = Abdominal Circumference
🦴 FL = Femur Length
⚖️ EFW = Estimated Fetal Weight
But remember, a centile is only one part of the picture.
A baby measuring on a lower centile isn’t automatically growth restricted, and a baby measuring on a higher centile isn’t automatically abnormally large. One of the important things to consider is the baby’s growth trajectory over time.
A baby who consistently follows a similar centile may simply be constitutionally smaller or larger. A significant change in growth trajectory may require further assessment, alongside the wider clinical picture.
📚 Student Midwife Tip:
Think of the centile as where the baby’s measurement sits compared with babies at the same gestation, and the growth trajectory as how that position changes over time.
Save this one for your next growth scan placement! 🤎
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