1. What Is Pregnancy Weeks Calculation?

Pregnancy weeks calculation determines how far along a pregnancy is based on the first day of the last menstrual period (LMP). This method is commonly used in obstetrics to estimate gestational age and due date.

2. How Does The Calculator Work?

The calculator uses the standard pregnancy dating formula:

Where:

• \( \text{LMP} \) — First day of last menstrual period
• \( \text{Current Date} \) — Today's date or any specified date
• \( \left\lfloor \right\rfloor \) — Floor function (rounding down to nearest whole number)

Explanation: The calculation counts the number of complete weeks that have passed since the first day of the last menstrual period.

3. Importance Of Pregnancy Dating

Details: Accurate pregnancy dating is essential for monitoring fetal development, scheduling prenatal tests, determining due date, and making important clinical decisions throughout pregnancy.

4. Using The Calculator

Tips: Enter the first day of your last menstrual period and the current date (defaults to today). Ensure dates are entered in the correct format and that LMP date is before current date.

5. Frequently Asked Questions (FAQ)

Q1: Why use LMP instead of conception date?
A: LMP is more reliably known than conception date and is the standard method used by healthcare providers worldwide for pregnancy dating.

Q2: How accurate is this calculation?
A: This method provides a good estimate, but ultrasound dating in early pregnancy (especially first trimester) is more accurate for determining gestational age.

Q3: What if I have irregular periods?
A: If cycles are irregular, LMP dating may be less accurate. An early ultrasound provides the most reliable dating in such cases.

Q4: When should I see a healthcare provider?
A: Schedule your first prenatal appointment when you get a positive pregnancy test, typically around 8 weeks gestational age.

Q5: How is due date calculated?
A: Due date is typically calculated as LMP + 280 days (40 weeks), known as Naegele's rule.