Last Menstrual Period (LMP): What Every Woman Should Know
Your last menstrual period (LMP) isn’t just about tracking your cycle—it’s the key to understanding your fertility, pregnancy due date, and overall health. But let’s be real: periods can be confusing!
Maybe you’re trying to get pregnant, worried about a late period, or just want to know what’s “normal.” Whatever your reason, this guide will explain LMP in simple words—no medical jargon, just clear answers.
What Exactly Is LMP?
Your LMP is the first day of your last period (not the last day!). Doctors use this date to:
📅 Calculate your pregnancy due date (“You’re how many weeks pregnant?!”).
🩺 Check for irregular cycles (Is your period late, early, or MIA?).
💡 Understand your fertility window (Best time to try for a baby).
How to Track Your LMP (The Right Way!)
- Mark Day 1 – The first day you see red blood (not just spotting).
- Note the length – Most cycles are 21–35 days (from Day 1 of one period to Day 1 of the next).
- Use an app – Like Flo, Clue, or even your phone’s calendar.
❓ “What if my periods are irregular?”
- Track for 3–6 months to see your average cycle.
- If it’s always unpredictable, talk to a doctor (could be PCOS, stress, or thyroid issues).
LMP and Pregnancy: Why It Matters
1. Calculating Your Due Date
Doctors use a simple “40-week rule” from your LMP:
LMP + 7 days – 3 months + 1 year = Due date
(Example: LMP April 10 → Due date January 17 next year!)
⚠ But… This assumes a 28-day cycle. If yours is longer/shorter, your real due date might differ (ultrasounds fix this later).
2. Figuring Out How Pregnant You Are
- “4 weeks pregnant” = 2 weeks after conception (yes, it’s weird!).
- Early ultrasounds adjust this based on baby’s size.
“My Period Is Late—Am I Pregnant?”
Maybe! But other reasons include:
😴 Stress (Work, sleep, life—it messes with cycles!).
💪 Too much exercise (Athletes often miss periods).
🍎 Weight changes (Sudden loss/gain affects hormones).
💊 Medications (Birth control, antibiotics, etc.).
What to do?
- Take a pregnancy test (after 1 week late).
- If negative but still no period, wait 2–3 months or see a doctor.
When to Worry About Your LMP
Call your doctor if:
🚨 No period for 3+ months (And you’re not pregnant).
🚨 Heavy bleeding (Soaking a pad every hour).
🚨 Severe pain (Worse than usual cramps).
