Pregnancy Week Calculator by LMP: Track Your Pregnancy Journey

Finding out you’re pregnant is an exciting moment! One of the first things you’ll want to know is how far along you are and when your baby is due. Our Pregnancy Week Calculator by LMP (Last Menstrual Period) helps you estimate your pregnancy stage and due date based on the first day of your last period.

How Does the Pregnancy Week Calculator Work? Doctors typically calculate your pregnancy weeks using the first day of your last menstrual period (LMP). This method assumes a 28-day cycle with ovulation happening around day 14. Even if you don’t have a perfect cycle, this is still a useful starting point.

Here’s how it works:

• Your pregnancy starts from the first day of your last period, not from the day you conceived.
• Pregnancy lasts around 280 days (40 weeks) from LMP.
• If you know your LMP, simply count forward 40 weeks to estimate your due date.

Why Use LMP to Calculate Pregnancy Weeks? The LMP method is widely used because it’s simple and doesn’t require an early ultrasound. Many women don’t know exactly when they ovulated, but most can recall the first day of their last period.

Key Pregnancy Milestones Based on LMP

• Week 4-5: You may get a positive pregnancy test.
• Week 8-12: Your first ultrasound (dating scan) helps confirm your due date.
• Week 18-20: Anatomy scan reveals baby’s growth and gender (if you choose to know).
• Week 24-28: Glucose test for gestational diabetes.
• Week 37-40: Your baby is full-term and ready to arrive any day!

Can Your Due Date Change? Yes! If an ultrasound scan shows that your baby is developing ahead or behind your LMP-based calculation, your doctor may adjust your due date. This is common if you have irregular cycles or don’t recall your last period accurately.

LMP vs. Ultrasound: Which is More Accurate?

• If your cycles are regular, LMP gives a good estimate.
• Early ultrasounds (8-12 weeks) are more accurate if your LMP date is uncertain.
• Later ultrasounds may not be as precise for dating, as babies grow at different rates.

Final Thoughts Your pregnancy journey is unique, and estimating your due date with the Pregnancy Week Calculator by LMP is just the beginning. Always check with your doctor for the most accurate timeline, and enjoy every step of this beautiful journey to meeting your little one!

• Moore, Keith. 2015. “How accurate are ‘due dates’?” BBC, February 3, 2015. www.bbc.com/news/magazine-31046144.
• Wikipedia: The Free Encyclopedia. 2017. en.wikipedia.org/wiki/Pregnancy.
• PubMed Health. 2014. “Pregnancy and birth: When your baby’s due date has passed.” www.ncbi.nlm.nih.gov/pubmedhealth/PMH0072755/.