Pregnancy Calculator

How is the Due Date Calculated?

The due date is calculated using Naegele's Rule, which adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day menstrual cycle with ovulation occurring on day 14. While this is an estimation, it's the standard method used by healthcare providers worldwide. Only about 5% of babies are born on their exact due date, with most arriving within two weeks before or after.

Formula: LMP + 280 days = Estimated Due Date

The Three Trimesters

Pregnancy is divided into three trimesters, each lasting approximately 13 weeks:

• First Trimester (Weeks 1-13): Major organs and structures develop. Common symptoms include morning sickness, fatigue, and breast tenderness.
• Second Trimester (Weeks 14-27): Often called the "honeymoon period" with increased energy. Baby's movements become noticeable.
• Third Trimester (Weeks 28-40): Final growth phase. Baby gains weight and prepares for birth. Common symptoms include back pain and frequent urination.

Important Milestones

Key pregnancy milestones include:

• Week 8: Baby's heart is fully formed and beating
• Week 12: End of first trimester, reduced miscarriage risk
• Week 20: Anatomy scan typically performed
• Week 24: Viability milestone (baby could survive with medical care)
• Week 37: Full-term pregnancy begins
• Week 40: Estimated due date

Calculation Methods Explained

• LMP Method: Most common, adds 280 days from first day of last period
• Conception Date: Estimated date of fertilization, calculated back 14 days from LMP
• Ultrasound: Most accurate, especially in first trimester, based on fetal measurements
• IVF Transfer: Calculated from embryo transfer date, accounting for embryo age (Day 3 or Day 5)

Accuracy and Limitations

This calculator provides an estimate based on standard calculations. The actual due date may vary based on several factors including cycle length, ovulation timing, and individual variations. First-trimester ultrasounds are the most accurate way to determine gestational age and due date. Always consult with your healthcare provider for personalized medical advice and accurate pregnancy dating.

Note: This is an educational tool and should not replace medical advice from qualified healthcare professionals.