1. What is Gestational Age Calculation?

Gestational age calculation based on Last Menstrual Period (LMP) is a standard method used in obstetrics to determine the duration of pregnancy. It provides an estimate of how far along a pregnancy has progressed from the first day of the woman's last menstrual period.

2. How Does the Calculator Work?

The calculator uses the gestational age formula:

Where:

• \( Current Date \) — The date for which gestational age is being calculated
• \( LMP \) — First day of Last Menstrual Period
• \( \lfloor \rfloor \) — Floor function (rounding down to nearest whole number)

Explanation: The calculation determines the number of complete weeks that have passed since the first day of the last menstrual period, providing the gestational age in weeks.

3. Importance of Gestational Age

Details: Accurate gestational age calculation is essential for monitoring fetal development, scheduling prenatal tests, determining expected delivery date, and making critical clinical decisions throughout pregnancy.

4. Using the Calculator

Tips: Enter the current date and the first day of the last menstrual period. Ensure dates are accurate as even small errors can affect the calculated gestational age by several days.

5. Frequently Asked Questions (FAQ)

Q1: Why use LMP instead of conception date?
A: LMP is used because it's typically more reliably known than the actual conception date and provides a standardized reference point for pregnancy dating.

Q2: How accurate is LMP-based gestational age?
A: LMP dating is generally accurate within ±2 weeks. First-trimester ultrasound is considered more accurate for dating pregnancies.

Q3: What if menstrual cycles are irregular?
A: For women with irregular cycles, LMP dating may be less accurate. Ultrasound dating is recommended in these cases.

Q4: When should gestational age be confirmed by ultrasound?
A: Early ultrasound (before 14 weeks) is recommended to confirm dating, especially if LMP is uncertain or cycles are irregular.

Q5: How does this relate to estimated due date?
A: Estimated due date (EDD) is calculated as LMP + 280 days (40 weeks). This calculator shows current gestational age from that starting point.