Quickly check fetal gestational age using ultrasound measurements like Crown-Rump Length (CRL) and Head Circumference (HC). Covers all trimesters to help you track fetal development.
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Faced with professional data like CRL and BPD in prenatal ultrasound reports, many expectant parents find it difficult to understand the corresponding fetal development stage. The fetal gestational age chart is a medical reference tool. By inputting ultrasound measurements such as Crown-Rump Length (CRL) and Head Circumference (HC) in millimeters, it outputs the corresponding gestational weeks and days (e.g., 12+3). Based on first-trimester CRL charts and multi-parameter charts for the second and third trimesters, this tool translates abstract measurement data into an intuitive reference for developmental progress.
Q: What does a gestational age of "10+2 weeks" mean?
A: It means you are exactly 10 weeks and 2 days pregnant. This "weeks + days" format is the standard obstetric dating method.
Q: Why are different measurement metrics used in the first trimester versus the second and third trimesters?
A: In the first trimester (≤14 weeks), fetal development is uniform, and CRL is internationally recognized as the most accurate metric. In the second and third trimesters, individual differences increase, requiring a comprehensive assessment using multiple parameters like BPD (Biparietal Diameter) and FL (Femur Length). This tool provides itemized charts to assist in your evaluation.
The results from this tool are for prenatal reference only and cannot replace a doctor's diagnosis. Ultrasound measurements must be performed by a professional physician. When inputting data, ensure all units are in millimeters. If the values fall outside the chart's range or if there are significant discrepancies between different metrics, we recommend consulting your obstetrician with your complete report. The measurement error for CRL in the first trimester is usually ≤3 days, while third-trimester parameters may be affected by fetal position.
Clinically, it is recommended to prioritize CRL for assessing gestational age between 7 and 13 weeks, as the margin of error is smallest during this period. After 20 weeks, it is advisable to comprehensively evaluate four metrics: BPD, HC, AC (Abdominal Circumference), and FL. Observing the growth trend is more meaningful than looking at a single absolute value. For example, if a fetus at 24 weeks has a BPD of 58mm (corresponding to 24+1) and an FL of 42mm (corresponding to 24+5), the overall proportionality should be assessed in conjunction with growth curves.
