One of the most exciting moments in early pregnancy is the first ultrasound, often called the 'dating scan.' It's your first glimpse of your baby and, more importantly, it provides the most accurate information for determining your Estimated Due Date (EDD). This calculator is designed to help you understand how sonographers and doctors use your baby's earliest measurements to establish a precise pregnancy timeline.
By using the data from your ultrasound report, you can see for yourself how your baby's growth translates into a due date.
What is an Ultrasound Dating Scan?
A dating scan is an ultrasound performed in the first trimester of pregnancy. Its primary purposes are to confirm that the pregnancy is viable (has a heartbeat), is located correctly in the uterus, and to measure the embryo or fetus to accurately determine the gestational age. Because all healthy fetuses grow at a very predictable rate in early pregnancy, these initial measurements provide the most reliable due to date, which is considered the 'gold standard' by medical professionals.
How to Use the Ultrasound Due Date Calculator
This tool can calculate your due date based on measurements from either a first or second-trimester scan. You will need your ultrasound report to find the following information:
- For a First Trimester Scan (most accurate): Enter the Crown-Rump Length (CRL) measurement and the date of your ultrasound.
- For a Second Trimester Scan: Enter the biometric measurements, which may include Biparietal Diameter (BPD), Head Circumference (HC), Abdominal Circumference (AC), and Femur Length (FL), along with the date of your ultrasound.
Decoding Your Ultrasound Report: What Do the Measurements Mean?
Your ultrasound report can look like a series of confusing acronyms, but they're simple once you know what they stand for:
- CRL (Crown-Rump Length): The measurement from the top of the baby's head to the bottom of their torso. It is the most accurate measure of fetal age in the first trimester.
- BPD (Biparietal Diameter): The diameter of the baby's head between the two parietal bones (the widest part).
- HC (Head Circumference): The measurement around the baby's head.
- AC (Abdominal Circumference): The measurement around the baby's abdomen, used to gauge growth and weight.
- FL (Femur Length): The length of the baby's thigh bone, which reflects longitudinal growth.
Important Medical Notes
This calculator is an educational tool to help you understand the data on your medical reports. The official due date used for your medical care is the one determined by your sonographer and confirmed by your doctor. Always use the EDD in your official medical records for scheduling and planning purposes.