Cerebroplacental ratio (CPR) reference values (MCA-PI/UA-PI) in singleton pregnancies, third trimester
Normal reference values for the cerebroplacental ratio (CPR) calculated as MCA-PI / UA-PI were reported for low-risk, normal-growth singleton fetuses across 29–41 weeks of gestation in the Israeli population study by Rambam Maimonides Medical Journal. [1]
Gestational-age specific reference percentiles for CPR (MCA-PI/UA-PI)
Reported percentiles: 5th, 10th, 25th, median (50th), 75th, with additional mean, minimum, and maximum values. [1]
| Gestational age (weeks) | 5th | 10th | 25th | 50th (median) | 75th |
|---|---|---|---|---|---|
| 29 | 0.90 | 0.92 | 1.04 | 1.30 | 1.80 |
| 30 | 0.70 | 0.72 | 0.83 | 1.50 | 1.80 |
| 31 | 1.00 | 1.00 | 1.17 | 1.50 | 1.98 |
| 32 | 1.00 | 1.09 | 1.30 | 1.60 | 2.10 |
| 33 | 1.30 | 1.30 | 1.30 | 1.60 | 2.20 |
| 34 | 0.80 | 1.01 | 1.12 | 1.34 | 2.03 |
| 35 | 1.06 | 1.09 | 1.40 | 1.70 | 2.03 |
| 36 | 0.70 | 0.98 | 1.10 | 1.50 | 1.80 |
| 37 | 0.74 | 1.03 | 1.13 | 1.46 | 1.80 |
| 38 | 0.68 | 1.09 | 1.10 | 1.39 | 1.68 |
| 39 | 0.78 | 0.89 | 1.01 | 1.30 | 1.64 |
| 40 | 1.05 | 1.08 | 1.14 | 1.32 | 1.61 |
| 41 | 0.60 | 0.60 | 1.00 | 1.46 | 1.85 |
[1]
Clinical interpretation threshold referenced in the same CPR framework
In a separate study using the same CPR definition (MCA-PI/UA-PI), a CPR < 1.0 was used as the abnormal threshold for adverse perinatal outcomes in pregnancies with intrauterine growth restriction. [2]
Scope and measurement convention for the reference ranges
The reference nomogram values apply to singleton pregnancies with normal anatomy and normal third-trimester estimated fetal weight, measured during the third trimester 29–41 weeks in the Israeli study setting. [1]