BPD of 50 mm (alone)
- Input
- DBP: 50 mm
- Expected output
- 21 semanas e 1 dia · margem ± 1,5 semana
Falls in the range where the mid-pregnancy anatomy scan is commonly performed.
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gestational age BPD second trimester fetal biometry
From week 14 onward, CRL falls outside its usage range and the calculator switches to estimating gestational age from BPD, HC, AC or FL, each with its own Hadlock formula and its own margin of error. This page shows how each measurement converts a value in millimeters into a gestational age, and how the calculator combines two or more measurements when they disagree.
Falls in the range where the mid-pregnancy anatomy scan is commonly performed.
It is the largest margin of error among the five measurements the calculator accepts.
The displayed margin is always the worst among the combined measurements, not an average of the margins, so it stays at 2.5 weeks even with BPD included.
CRL (Crown-Rump Length) in the 1st trimester (weeks 6–14) is the most precise parameter, with a margin of error of only ± 3–5 days. After week 14, composite biometry (BPD + HC + AC + FL) tends to be more accurate than any single measurement. Precision decreases progressively throughout gestation.
A percentile indicates where the fetal measurement sits relative to a reference population at the same gestational age; the 50th percentile is the median. The calculator itself does not compute a percentile, it only converts millimeters into weeks using the Hadlock formulas, the comparison against percentile curves is done separately, by whoever interprets the report.
Because fetal growth becomes less uniform after the first trimester: genetic, nutritional and individual factors start to influence the size of each structure more. The calculator reflects that with margins of 1.5 to 2.5 weeks for these measurements, versus a fixed 0.5 week for CRL.
Yes, as long as none of them is CRL. BPD, HC, AC and FL carry equal weight against each other in the weighted average; only CRL gets a doubled weight when it appears alongside another measurement.
Medical disclaimer: this calculation is educational and does not replace physician evaluation. Biometric measurements have inherent margin of error and must always be interpreted in clinical context.
Select the biometric measurement type from your ultrasound report, enter the value in millimeters, and optionally enter the exam date to get the estimated EDD.
Values entered remain only in your browser. We do not store or transmit this data.