What is difference between gestational age and fetal age?

Gestational age counts from LMP. Fetal age counts from conception — approximately 2 weeks less.

Pregnancy Week Calculator — How Many Weeks Pregnant Am I?

How Pregnancy Weeks Are Counted

Pregnancy is measured from the first day of your last menstrual period (LMP), not from conception. This means during "weeks 1–2" you haven't actually conceived yet — ovulation happens around week 2, and conception occurs shortly after. Full-term pregnancy is 40 weeks from LMP.

What Happens Each Trimester

First Trimester (Weeks 1–13): Most critical for organ formation. Morning sickness peaks at 8–10 weeks. Miscarriage risk highest here.
Second Trimester (Weeks 14–27): The golden trimester — energy returns, bump shows, first movements (quickening) felt at 18–22 weeks.
Third Trimester (Weeks 28–40): Rapid baby weight gain. Braxton Hicks, back pain, heartburn are common. Baby settles into birth position.

What if my ultrasound shows a different week?

Ultrasound dating is more accurate than LMP dating, especially for irregular cycles. If there's a discrepancy of more than 7 days before 14 weeks, your doctor may adjust your due date based on ultrasound measurements.

Medical Disclaimer: This tool is for educational purposes only and should not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider for personalized guidance.

How Many Weeks Pregnant Are You?

Knowing exactly how many weeks pregnant you are helps you understand your baby's current stage of development, what symptoms to expect, and what prenatal appointments and tests are coming up. Our pregnancy week calculator gives you your exact gestational age based on your last menstrual period.

Key Pregnancy Milestones by Week

Week 4: Missed period, hCG detectable, pregnancy test positive
Week 6: Heartbeat visible on transvaginal ultrasound
Week 8: All major organs forming, baby the size of a raspberry
Week 12: End of first trimester, miscarriage risk drops significantly
Week 16: Gender may be detectable by ultrasound
Week 20: Anatomy scan, halfway point!
Week 24: Viability milestone
Week 28: Third trimester begins
Week 37: Early term — baby is ready if labor begins
Week 40: Your estimated due date

Why does pregnancy count from last period not conception?

Because most women know when their period started but not when they ovulated or conceived, LMP dating is used as a reliable reference point. Conception typically occurs 2 weeks after LMP.

Can I be further along than I think?

Yes. If you ovulated earlier or later than day 14, your gestational age may differ from LMP calculations. An early ultrasound provides the most accurate dating.

What is the difference between gestational age and fetal age?

Gestational age counts from LMP (when your doctor tracks pregnancy). Fetal age counts from conception — so fetal age is approximately 2 weeks less than gestational age.

Pregnancy Week Calculator

How Many Weeks Pregnant?

How Pregnancy Weeks Are Counted

What Happens Each Trimester

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