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Pregnancy Weeks Calculation:
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The Weeks Pregnant Calculator By LMP estimates gestational age based on the first day of your last menstrual period (LMP). This is the standard method used by healthcare providers to calculate pregnancy duration and estimate due dates.
The calculator uses the following formula:
Where:
Explanation: Pregnancy is calculated from the first day of your last menstrual period, not from conception. This adds approximately 2 weeks to the actual fetal age.
Details: Accurate pregnancy dating is crucial for monitoring fetal development, scheduling prenatal tests, determining viability, and calculating the estimated due date. Proper dating helps identify potential complications and ensures appropriate prenatal care.
Tips: Enter the first day of your last menstrual period and the current date (or any date you want to calculate for). The calculator will determine how many weeks pregnant you are at that specific date.
Q1: Why is pregnancy calculated from LMP instead of conception?
A: LMP provides a consistent reference point that's easier to recall than conception date. Most women know their LMP but rarely know exact conception date.
Q2: How accurate is LMP dating?
A: LMP dating is generally accurate for women with regular 28-day cycles. For irregular cycles or uncertain dates, ultrasound dating is more reliable.
Q3: What if I don't remember my exact LMP?
A: Use your best estimate. Early pregnancy ultrasound (before 14 weeks) can provide more accurate dating if LMP is uncertain.
Q4: Does this work for IVF pregnancies?
A: For IVF pregnancies, dating is typically calculated from embryo transfer date plus 14 days, or from retrieval date plus 14 days.
Q5: When should I confirm with healthcare provider?
A: Always confirm pregnancy dating with your healthcare provider, who may adjust based on ultrasound measurements and clinical assessment.