CRL(Crown Rump Length) varies from week by week and also day by day. A good increasing CRL means your baby is growing as expected without any issues. The normal CRL at 8 week ranges anywhere from 16.5mm to 24.5mm.
As per the Intergrowth table, the Normal CRL (Crown Rump Length) at 8 weeks 5 days or 6 days should be above 24 mm and it also differs according to percentile.
| Gestational Age | CRL (in mm) |
|---|---|
| 8 Weeks 0 days | 16.5 – 17.5 mm |
| 8 Weeks 1 days | 18.0 -18.5 mm |
| 8 Weeks 2 days | 19.0 – 20.0 mm |
| 8 Weeks 3 days | 20.5 – 21.0 mm |
| 8 Weeks 4 days | 21.5 – 22.0 mm |
| 8 Weeks 5 days | 22.5 – 23.5 mm |
| 8 Weeks 6 days | 24.0 – 24.5 mm |
If the baby is measuring higher than these CRL mentioned in the above table, you need not worry as there is a chance that CRL measurement might be wrong (or) your ovulation date and LMP might have been miscalculated!
References:
https://linkinghub.elsevier.com/retrieve/pii/S0301211509002383
https://intergrowth21.tghn.org/
https://www.hindawi.com/journals/isrn/2012/938583/tab4/