Discovering you're pregnant is life-changing, and understanding your pregnancy timeline helps you prepare for each stage of this incredible journey.
How Pregnancy Due Date is Calculated
Pregnancy is counted from the first day of your last menstrual period (LMP), not conception. The standard calculation uses Naegele's Rule:
Due Date = LMP + 1 year - 3 months + 7 days
Example: LMP January 1, 2024 Due Date = October 8, 2024
Why This Method?
Conception typically occurs around day 14 of your cycle (ovulation). Since exact conception date is often unknown, counting from LMP provides a standardized starting point.
Understanding Pregnancy Terms
• Gestational Age: Weeks since LMP (used by doctors) • Fetal Age: Actual age since conception (2 weeks less) • Full Term: 39-40 weeks • Early Term: 37-38 weeks • Late Term: 41 weeks • Post Term: 42+ weeks
First Trimester (Weeks 1-12)
What's Happening: • Week 4: Implantation occurs • Week 5: Heart begins beating • Week 6: Neural tube forms • Week 8: All major organs developing • Week 10: Called a fetus now • Week 12: Gender may be visible on ultrasound
Common Symptoms: • Morning sickness (weeks 6-12) • Fatigue • Breast tenderness • Frequent urination • Mood swings
Important Appointments: • First prenatal visit (week 8-10) • Dating ultrasound • Blood tests and screenings
Second Trimester (Weeks 13-26)
What's Happening: • Week 14: Baby can make facial expressions • Week 16: Gender identifiable • Week 18: Baby starts moving (quickening) • Week 20: Halfway point, anatomy scan • Week 24: Viability milestone
Common Symptoms: • Increased energy • Baby movement felt • Growing belly visible • Back pain may start • Braxton Hicks contractions
Important Appointments: • Anatomy scan (week 18-22) • Glucose screening (week 24-28) • Regular growth monitoring
Third Trimester (Weeks 27-40)
What's Happening: • Week 28: Eyes can open • Week 32: Bones hardening • Week 36: Baby moves head-down • Week 37: Considered early term • Week 40: Due date!
Common Symptoms: • Shortness of breath • Swelling in feet/ankles • Frequent urination returns • Braxton Hicks increase • Nesting instinct
Important Appointments: • Weekly visits from week 36 • Group B strep test (week 35-37) • Fetal monitoring
Key Milestones and Tests
Week 10-13: NIPT (Non-Invasive Prenatal Testing) Week 11-14: Nuchal translucency scan Week 15-20: Amniocentesis (if indicated) Week 18-22: Detailed anatomy scan Week 24-28: Glucose tolerance test Week 35-37: Group B strep test
Factors Affecting Due Date Accuracy
Your due date may change based on: • Irregular menstrual cycles • First ultrasound measurements • IVF transfer date (if applicable) • Multiple gestations
Only 5% of babies arrive on their due date. Most arrive between 38-42 weeks.
Warning Signs to Watch
Contact your doctor immediately if you experience: • Heavy bleeding • Severe abdominal pain • High fever • Severe headaches with vision changes • Decreased fetal movement • Leaking fluid
Preparing for Baby
First Trimester: • Choose a healthcare provider • Start prenatal vitamins • Avoid alcohol, tobacco, certain foods
Second Trimester: • Start baby registry • Consider childbirth classes • Begin nursery planning
Third Trimester: • Pack hospital bag • Install car seat • Finalize birth plan • Prepare home for baby
Use our Pregnancy Calculator to determine your due date, current week, and trimester. Remember, every pregnancy is unique—regular prenatal care is essential for a healthy pregnancy.