GA (days) = assessment date − LMP · EDD = LMP + 280 days
GA by CRL (days) = 8.052 × √CRL(mm) + 23.73
IVF: EDD = transfer date + 266 − embryo age (days)
GA(BPD) = 9.54 + 1.482x + 0.1676x² · GA(HC) = 8.96 + 0.54x + 0.0003x³ (x in cm)
GA(AC) = 8.14 + 0.753x + 0.0036x² · GA(FL) = 10.35 + 2.46x + 0.17x² (x in cm)
Composite GA = 10.85 + 0.0006·HC·FL + 0.067·BPD + 0.0168·AC (mm)
log10 EFW = 1.5662 − 0.0108·HC + 0.0468·AC + 0.171·FL + 0.00034·HC² − 0.003685·AC·FL (cm)
AFI = sum of the deepest vertical pocket in each of four quadrants
Each vessel against its default reference · CPR = MCA PI ÷ UA PI · stage by the Barcelona protocol when EFW is below the 10th centile
Centile and z-score of the PI for gestational age · flag above the 95th centile
Centile and z-score of the PI for gestational age · flag below the 5th centile (cerebral vasodilatation)
PIV = (S − a) ÷ time-averaged maximum velocity · centile for gestational age, or for CRL at 11 to 14 weeks
Expected median (cm/s) = e^(2.31 + 0.04643 × GA in weeks) · MoM = observed ÷ median
Fetoplacental volume (mL) = 1.046 + 0.14 × weight (g)
Volume to transfuse (mL) = fetoplacental volume × (target − fetal) ÷ donor
LHR = lung area (mm²) ÷ head circumference (mm)
Expected, right lung = −2.2481 + 0.2712·GA − 0.0033·GA²
Expected, left lung = −1.4815 + 0.1824·GA − 0.0023·GA²
Mean PI = (left + right) ÷ 2 · centile for gestational age · flag above the 95th centile
Discordance (%) = (larger − smaller) ÷ larger × 100
CPR = middle cerebral artery PI ÷ umbilical artery PI · compared with the 5th centile for gestational age
Volume (cm³) = length × width × height × 0.52CVR = volume ÷ head circumference (cm)
Score = sum of five components, each 0 or 2 (out of 8 when monitoring is not done)
Score = dilation + effacement + station + consistency + position (0 to 13)
BMI = weight (kg) ÷ height (m)²
Doubling time = hours × ln 2 ÷ ln(second ÷ first)Change in 48 h (%) = ((second ÷ first)^(48 ÷ hours) − 1) × 100
Mean arterial pressure = (systolic + 2 × diastolic) ÷ 3Protein-to-creatinine ratio = protein ÷ creatinine (both in mg/dL)
Iron deficit (mg) = weight × (target − current haemoglobin) × 2.4 + 500
Volume (cm³) = 0.5 × length × anteroposterior × transverse ÷ 1000