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Obstetric — calculator & tables

Obstetric — calculator & tables — Reference values: CRL → GA (Robinson-Fleming), CRL → GA (INTERGROWTH-21st), Estimated fetal weight (Hadlock IV).

Measurements and reference values

MeasurementUsual valueNote
CRL → GA (Robinson-Fleming)IG(dias) = 8,052·√(CCN·1,037) + 23,73CRL in mm (5–84 mm)Source: Robinson & Fleming 1975
CRL → GA (INTERGROWTH-21st)IG(dias) = 59,3615 + 0,4614·CCNvalid 11+0–13+6 wkSource: INTERGROWTH-21st 2014
Estimated fetal weight (Hadlock IV)log10(PFE)=1,3596+0,0064·CC+0,0424·CA+0,174·CF+0,00061·DBP·CA−0,00386·CA·CFmeasurements in cm; EFW in gSource: Hadlock 1985
EFW — INTERGROWTH-21st (AC+HC)log(PFE)=5,084820−54,06633·(CA/100)³−95,80076·(CA/100)³·ln(CA/100)+3,136370·(CC/100)natural log; AC/HC in cm; 2nd world referenceSource: INTERGROWTH-21st (Stirnemann 2017)

Classifications and calculators

EFW by gestational age — Hadlock (g)

Wkp10p50p90
20275331387
21331399467
22398478559
23471568665
24556670784
25652785918
267589131068
2787610551234
28100412101416
29114513791613
30129415591824
31145317512049
32162119532285
33179421622530
34197323772781
35215425953036
36233528133291
37251330283543
38268632363786
39285134354019
40300436194234

SGA < p10 · AGA p10–p90 · LGA > p90. Use the calculator above for automatic classification. Second world reference: INTERGROWTH-21st (official table, Stirnemann 2017).

Source: Hadlock 1991, Table 1 — DOI 10.1148/radiology.181.1.1887021

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