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Last Period Calculation:
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The Pregnancy Calculator Using Last Period estimates the due date and current gestational age based on the first day of the woman's last menstrual period (LMP). This is one of the most common methods used to calculate pregnancy duration.
The calculator uses the standard last period calculation:
Where:
Explanation: This calculation is based on Naegele's rule, which assumes a 28-day menstrual cycle and ovulation occurring on day 14.
Details: Accurate due date estimation is crucial for monitoring fetal development, scheduling prenatal care, preparing for delivery, and identifying potential pregnancy complications.
Tips: Enter the first day of your last menstrual period. For best accuracy, use the exact date from your medical records. The calculator will provide your estimated due date and current gestational age.
Q1: How Accurate Is The Last Period Method?
A: It's reasonably accurate for women with regular 28-day cycles. For irregular cycles, ultrasound dating may be more precise.
Q2: What If I Don't Remember My Last Period Date?
A: If you're unsure about your LMP, an early pregnancy ultrasound (6-12 weeks) can provide a more accurate due date estimation.
Q3: Why 280 Days Instead Of 9 Months?
A: Pregnancy is calculated as 40 weeks from LMP, which equals 280 days. This accounts for the fact that conception typically occurs about 2 weeks after the first day of your last period.
Q4: Can The Due Date Change?
A: Yes, healthcare providers may adjust the due date based on ultrasound measurements, especially if there's a significant difference from the LMP calculation.
Q5: What Percentage Of Babies Are Born On Their Due Date?
A: Only about 5% of babies are born exactly on their due date. Most are born within two weeks before or after the estimated date.