When Does Pregnancy Officially Start? Understanding the First Day of Your Last Menstrual Period

Learn when pregnancy officially starts and how to calculate your due date using the last menstrual period method.

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Pregnancy officially starts from the first day of your last menstrual period (LMP). This is because ovulation and fertilization usually happen about two weeks after your period begins, making it difficult to pinpoint the exact moment of conception. Therefore, the LMP method provides a standardized way of calculating the pregnancy timeline and due date.

FAQs & Answers

  1. How is the due date calculated? The due date is typically calculated based on the first day of your last menstrual period, adding 280 days for a full-term pregnancy.
  2. What is ovulation? Ovulation is the process where an ovary releases an egg, which can be fertilized by sperm, and it usually occurs about two weeks after your last period.
  3. What if I don't remember my last menstrual period? If you don't remember your last menstrual period, your healthcare provider may use an ultrasound to estimate the gestational age of your pregnancy.

Watch More

For more insights on pregnancy and reproductive health, check out our videos on ovulation tracking and understanding your menstrual cycle.

  1. Understanding Pregnancy: Does Conception Count as Day 1? Explore why conception is not considered day 1 of pregnancy and how gestational age is calculated from your last menstrual period.
  2. How to Determine Your Pregnancy Week Learn how to accurately calculate your pregnancy week from your last menstrual period.
  3. How to Determine Your Pregnancy Week Correctly Learn how to accurately calculate your pregnancy week using the last menstrual period (LMP) method.
  4. Is 5 Weeks Pregnant Actually 3? Understanding Pregnancy Calculations Learn why 5 weeks pregnant is counted as 5 weeks and how pregnancy weeks are calculated from the last menstrual period.