Fetal Gestational Age Comparison Chart

Tool Introduction

"Fetal Gestational Age Chart" is a convenient online tool designed to help expectant mothers and medical professionals quickly estimate gestational age based on fetal ultrasound measurement data. This tool integrates two core types of reference charts: one is a gestational age estimation chart based on Crown-Rump Length (CRL), particularly suitable for gestational age assessment in early pregnancy; the other is a gestational age estimation chart based on single measurement indicators (such as Head Circumference HC, Biparietal Diameter BPD, Femur Length FL, Transcerebellar Diameter TCD, Foot Length FoL), suitable for gestational age estimation in mid-to-late pregnancy. By entering the corresponding data from your ultrasound report, you can easily find the estimated gestational age of the current fetus, thereby better understanding the fetal development.

Principle of Gestational Age Estimation

Estimating fetal gestational age is crucial throughout pregnancy, as it relates to determining the due date, assessing fetal growth and development, and arranging various prenatal check-ups. This tool adopts two main estimation principles based on the physiological characteristics of the fetus at different developmental stages:

• Early Pregnancy Estimation (based on Crown-Rump Length CRL): In early pregnancy (usually before 14 weeks of gestation), fetal growth rate is relatively stable and individual differences are small. Crown-Rump Length (CRL) is an internationally recognized and most accurate indicator for gestational age assessment. By measuring the longest distance from the top of the embryo's or fetus's head to its rump, combined with the corresponding reference chart, gestational age can be accurately estimated.
• Mid-to-Late Pregnancy Estimation (based on multiple physiological indicators): After entering mid-to-late pregnancy, individual differences in fetal growth and development begin to appear, and the accuracy of a single indicator will decrease. Therefore, this tool provides reference charts for multiple measurement indicators such as Head Circumference (HC), Biparietal Diameter (BPD), Femur Length (FL), Transcerebellar Diameter (TCD), and Foot Length (FoL). Doctors usually make a comprehensive judgment based on these indicators, and this tool can serve as a reference to help you understand the gestational age range corresponding to each indicator.

How to Use

1. Obtain Ultrasound Measurement Data: You will need a recent fetal ultrasound examination report.
2. Determine Pregnancy Stage: Based on your number of weeks of pregnancy, select the appropriate reference chart:
   • If you are in early pregnancy (usually before 14 weeks of gestation), please use the "Gestational Age Estimation Chart based on Crown-Rump Length (CRL)".
   • If you are in mid-to-late pregnancy, please use the "Gestational Age Estimation Chart based on Single Measurement Indicators".
3. Find Corresponding Data:
   • Early Pregnancy: Find the fetal "Crown-Rump Length (CRL)" value in the ultrasound report, the unit is usually millimeters (mm). In the first table of this tool, find the row closest to your CRL value.
   • Mid-to-Late Pregnancy: Find the measurement indicator value you wish to query in the ultrasound report, such as "Head Circumference (HC)", "Biparietal Diameter (BPD)", "Femur Length (FL)", etc., the unit is usually millimeters (mm). In the second table of this tool, find the row in the corresponding indicator column that is closest to your measured value.
4. Obtain Estimated Gestational Age: The "Gestational Age" corresponding to your measured value in the reference chart is the estimated result. The gestational age format is "weeks + days", for example, "8+3" means 8 weeks and 3 days.

Usage Examples

Here are a few examples of using this tool to estimate gestational age:

• Example 1: Early Pregnancy CRL Estimation
  • Input Data: Ultrasound report shows fetal Crown-Rump Length (CRL) is 35mm.
  • Operation Demonstration: In the "Gestational Age Estimation Chart based on Crown-Rump Length (CRL)", find the row corresponding to CRL 35mm.
  • Expected Output Result: Estimated gestational age is 10+2 weeks.
• Example 2: Mid-to-Late Pregnancy BPD Estimation
  • Input Data: Ultrasound report shows fetal Biparietal Diameter (BPD) is 50mm.
  • Operation Demonstration: In the "Gestational Age Estimation Chart based on Single Measurement Indicators", find the row corresponding to BPD 50mm.
  • Expected Output Result: Estimated gestational age is 21+0 weeks.
• Example 3: Mid-to-Late Pregnancy FL Estimation
  • Input Data: Ultrasound report shows fetal Femur Length (FL) is 40mm.
  • Operation Demonstration: In the "Gestational Age Estimation Chart based on Single Measurement Indicators", find the row corresponding to FL 40mm.
  • Expected Output Result: Estimated gestational age is 23+6 weeks.

Frequently Asked Questions

• Q: What do CRL, HC, BPD, FL, TCD, FoL indicators represent respectively? A: These are important fetal ultrasound measurement indicators: CRL (Crown-Rump Length) is used in early pregnancy; HC (Head Circumference) and BPD (Biparietal Diameter) assess fetal head development; FL (Femur Length) assesses limb development; TCD (Transcerebellar Diameter) assesses cerebellar development; FoL (Foot Length) assesses foot development. They are all important references for estimating fetal gestational age and growth.
• Q: How to interpret the gestational age representation, for example, "10+2 weeks"? A: "10+2 weeks" means 10 full weeks of pregnancy, and 2 days have passed. Gestational age is usually expressed in the format of "weeks + days", for example, 10 weeks and 3 days is 10+3.
• Q: How accurate are these reference charts, and can they completely replace a doctor's diagnosis? A: These charts are reference values generated based on a large amount of medical statistical data and have high reference value under normal circumstances. However, there are individual differences in fetal growth and development, which are affected by various factors such as genetics, nutrition, and environment. The actual gestational age should be determined by a doctor based on a comprehensive judgment of multiple examinations (such as last menstrual period, early pregnancy ultrasound, and subsequent development). This tool is for auxiliary reference only and cannot replace professional medical diagnosis and advice.
• Q: What if the ultrasound measurement value is outside the table range? A: If your measured value is outside the table range, it may mean that fetal development is in an earlier or later stage, or there are other special circumstances. It is recommended to consult a professional doctor for interpretation and diagnosis.

Precautions

• The data provided by this tool is for reference only and cannot be used as the final medical diagnostic basis. For all decisions regarding fetal health, please be sure to consult a professional obstetrician-gynecologist.
• Please ensure that the entered measurement data is accurate and pay attention to the unit being millimeters (mm). Incorrect input will lead to incorrect gestational age estimation results.
• There are individual differences in fetal growth and development. Even with the same gestational age, the measurement data of different fetuses may vary slightly. This reference chart provides average reference values.
• The best timing for ultrasound examination and the selection of measurement indicators should follow the doctor's professional guidance. Early pregnancy CRL measurement is the most accurate period for assessing gestational age.