SONOGRAPHIC DATING

Ultrasound Due Date Calculator

Enter the scan date and gestational age documented on your official physician or sonographer ultrasound report to determine your official clinical due date.

Ultrasound-Derived Gestational Parameters ACOG Opinion No. 700

Official Ultrasound Due Date

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Current Gestational Age Today: —

Equivalent LMP Baseline

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Medical chart baseline

Current Trimester

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Progress stage

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Medical Notice: This calculator calculates dates based strictly on clinician-certified ultrasound measurements entered by the user. It does not interpret raw sonogram images or perform diagnostic image analysis. Always rely on your certified obstetrician's dating summary.

The Clinical Accuracy of Ultrasound Dating

According to consensus guidelines from the American College of Obstetricians and Gynecologists (ACOG), the American Institute of Ultrasound in Medicine (AIUM), and the Society for Maternal-Fetal Medicine (SMFM), first-trimester ultrasound measurement of Crown-Rump Length (CRL) is the single most accurate method for establishing or confirming gestational age.

Biometric Dating Across Trimesters

First Trimester (≤ 13 6/7 weeks): Crown-Rump Length (CRL) measurement has an accuracy margin of ±5 to 7 days.
Second Trimester (14 0/7 to 27 6/7 weeks): Combines Biparietal Diameter (BPD), Head Circumference (HC), Abdominal Circumference (AC), and Femur Length (FL), with an accuracy margin of ±7 to 14 days.
Third Trimester (≥ 28 0/7 weeks): Biometric accuracy decreases to ±21 to 30 days due to biological growth variation; ultrasound dating should not routinely alter a well-established first-trimester due date.

References

American College of Obstetricians and Gynecologists (ACOG). Committee Opinion No. 700: Methods for Estimating the Due Date. Obstet Gynecol 2017;129:e150-4.
Hadlock FP, Shah YP, Kanon DJ, Lindsey JV. Fetal crown-rump length: reevaluation of relation to menstrual age (5-18 weeks) with high-resolution real-time US. Radiology 1992;182(2):501-505.