Due Date Calculator from Ultrasound

Ultrasound Due Date Calculator

Use this calculator to estimate your baby's due date based on your first-trimester ultrasound measurements, specifically the Crown-Rump Length (CRL).

function calculateDueDateFromUltrasound() { var ultrasoundDateInput = document.getElementById("ultrasoundDate").value; var crlMeasurement = parseFloat(document.getElementById("crlMeasurement").value); var resultDiv = document.getElementById("result"); resultDiv.innerHTML = ""; // Clear previous results // Input validation if (!ultrasoundDateInput) { resultDiv.innerHTML = "Please enter the date of your ultrasound scan."; return; } if (isNaN(crlMeasurement) || crlMeasurement <= 0) { resultDiv.innerHTML = "Please enter a valid Crown-Rump Length (CRL) measurement."; return; } if (crlMeasurement 84) { resultDiv.innerHTML = "CRL measurements are typically used for dating between 5mm and 84mm (approx. 5 to 14 weeks gestation). Please ensure your CRL is within this range for accurate results."; return; } // Parse ultrasound date var ultrasoundDate = new Date(ultrasoundDateInput); if (isNaN(ultrasoundDate.getTime())) { resultDiv.innerHTML = "Invalid ultrasound date. Please use a valid date format."; return; } // Calculation based on Hadlock's formula (simplified for CRL) // Gestational Age (days) = 8.052 * sqrt(CRL in mm) + 23.73 var gestationalAgeDays = (8.052 * Math.sqrt(crlMeasurement)) + 23.73; var gestationalAgeWeeks = Math.floor(gestationalAgeDays / 7); var gestationalAgeRemainingDays = Math.round(gestationalAgeDays % 7); // Calculate estimated due date var estimatedDueDate = new Date(ultrasoundDate); estimatedDueDate.setDate(ultrasoundDate.getDate() + Math.round(gestationalAgeDays)); // Add calculated GA to ultrasound date // Format dates for display var options = { year: 'numeric', month: 'long', day: 'numeric' }; var formattedUltrasoundDate = ultrasoundDate.toLocaleDateString('en-US', options); var formattedEstimatedDueDate = estimatedDueDate.toLocaleDateString('en-US', options); resultDiv.innerHTML = "

Calculation Results:

" + "Ultrasound Date: " + formattedUltrasoundDate + "" + "Crown-Rump Length (CRL): " + crlMeasurement.toFixed(1) + " mm" + "Estimated Gestational Age at Scan: " + gestationalAgeWeeks + " weeks and " + gestationalAgeRemainingDays + " days" + "Estimated Due Date: " + formattedEstimatedDueDate + ""; } .calculator-container { font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; background-color: #f9f9f9; padding: 25px; border-radius: 10px; box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1); max-width: 600px; margin: 30px auto; border: 1px solid #e0e0e0; } .calculator-container h2 { color: #2c3e50; text-align: center; margin-bottom: 20px; font-size: 1.8em; } .calculator-container p { color: #34495e; line-height: 1.6; margin-bottom: 15px; } .calculator-form .form-group { margin-bottom: 18px; } .calculator-form label { display: block; margin-bottom: 8px; color: #34495e; font-weight: bold; font-size: 1em; } .calculator-form input[type="date"], .calculator-form input[type="number"] { width: calc(100% – 20px); padding: 12px; border: 1px solid #ccc; border-radius: 6px; font-size: 1em; box-sizing: border-box; transition: border-color 0.3s ease; } .calculator-form input[type="date"]:focus, .calculator-form input[type="number"]:focus { border-color: #007bff; outline: none; box-shadow: 0 0 5px rgba(0, 123, 255, 0.3); } .calculator-form button { background-color: #007bff; color: white; padding: 12px 25px; border: none; border-radius: 6px; cursor: pointer; font-size: 1.1em; font-weight: bold; display: block; width: 100%; transition: background-color 0.3s ease, transform 0.2s ease; margin-top: 20px; } .calculator-form button:hover { background-color: #0056b3; transform: translateY(-2px); } .calculator-result { margin-top: 25px; padding: 20px; background-color: #e9f7ff; border: 1px solid #b3e0ff; border-radius: 8px; color: #2c3e50; } .calculator-result h3 { color: #007bff; margin-top: 0; margin-bottom: 15px; font-size: 1.5em; text-align: center; } .calculator-result p { margin-bottom: 10px; font-size: 1.05em; } .calculator-result .highlight { color: #d9534f; font-weight: bold; font-size: 1.2em; } .calculator-result .error { color: #dc3545; font-weight: bold; text-align: center; }

Understanding Your Due Date from Ultrasound

Estimating your baby's due date is one of the most exciting parts of early pregnancy. While your last menstrual period (LMP) can provide an initial estimate, an early ultrasound scan, particularly one that measures the Crown-Rump Length (CRL), is often considered the most accurate method for dating a pregnancy.

Why is Ultrasound Dating More Accurate?

The accuracy of dating a pregnancy by LMP can be affected by irregular menstrual cycles, uncertainty about the exact date of the last period, or variations in ovulation. In contrast, during the first trimester (typically between 6 and 14 weeks of gestation), fetal growth is very consistent among embryos. This consistency allows for a highly reliable estimation of gestational age based on the baby's size.

What is Crown-Rump Length (CRL)?

The Crown-Rump Length (CRL) is the measurement of the length of the embryo or fetus from the top of its head (crown) to the bottom of its buttocks (rump). It's a crucial measurement taken during the first-trimester ultrasound. As the embryo grows rapidly and predictably during this period, the CRL provides an excellent indicator of its gestational age.

How the Calculator Works

This calculator uses a widely accepted formula, often based on research by Hadlock et al., to estimate gestational age from the CRL measurement. The formula translates the length of your baby in millimeters into an approximate number of days of gestation. Once the gestational age at the time of the ultrasound is determined, it's added to the date of your ultrasound scan to project your estimated due date.

For example, if your ultrasound was on January 1st and your baby's CRL indicated a gestational age of 9 weeks and 3 days, the calculator would add 9 weeks and 3 days to January 1st to determine your estimated due date.

Accuracy and Limitations

• High Accuracy: First-trimester ultrasound dating using CRL is generally considered accurate within +/- 5 to 7 days. This makes it more precise than LMP dating, especially if there's any doubt about your last period.
• Optimal Window: CRL measurements are most accurate for dating between approximately 6 and 14 weeks of gestation. Beyond this window, other measurements like biparietal diameter (BPD), head circumference (HC), and femur length (FL) become more reliable for dating.
• Individual Variation: While fetal growth is consistent in early pregnancy, slight individual variations can occur. The due date provided is an estimate, and only about 5% of babies are born exactly on their due date.

Why is an Accurate Due Date Important?

An accurate due date is vital for several reasons:

• Monitoring Fetal Growth: It helps healthcare providers track your baby's growth and development against expected milestones.
• Scheduling Tests: Many prenatal tests, such as screening for chromosomal abnormalities, are time-sensitive and need to be performed within specific gestational windows.
• Planning Delivery: It assists in making informed decisions about the timing of delivery, especially if there are complications or if an induction is considered.
• Emotional Preparation: Knowing your due date helps you and your family prepare emotionally and practically for the baby's arrival.

Always discuss your ultrasound results and estimated due date with your healthcare provider, as they will provide the most personalized and accurate information for your pregnancy journey.