🤰 Naegele's Rule📅 LMP or Conception📊 Trimester Breakdown
Pregnancy Due Date Calculator
Calculate your estimated due date (EDD) from your last menstrual period (LMP) or conception date, with a full trimester timeline.
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Naegele's Rule: Due date = LMP + 280 days (40 weeks). Full term is 39–40 weeks. Only ~4–5% of babies arrive on their exact due date. The EDD is a midpoint — deliveries between 37–42 weeks are considered normal.
How Due Dates Are Calculated Around the World
Despite cultural differences in how pregnancy is described, all modern medical systems use the same underlying formula: EDD = LMP + 280 days.
| Country | Medical Method | Cultural Note |
|---|---|---|
| 🇺🇸 USA | Naegele's Rule (280 days) | ACOG defines full-term as 39–40 weeks |
| 🇬🇧 UK | Naegele's Rule + ultrasound at ~12 weeks | NHS dates confirmed by dating scan |
| 🇯🇵 Japan | Same 280-day rule | Traditionally called "10-month pregnancy" counting from conception |
| 🇨🇳 China | Same 280-day rule | Traditional lunar calendar may add cultural milestones |
| 🇩🇪 Germany | Naegele's Rule | Mutterpass (mother's passport) tracks all milestones |
| 🇦🇺 Australia | Naegele's Rule + 12-week dating scan | RANZCOG recommends ultrasound confirmation |
| 🇮🇳 India | Same 280-day rule | Ayurvedic tradition counts "10 months" from conception |
Trimester Guide
- 1st Trimester (Weeks 1–13): Embryo implants and major organs form. Morning sickness, fatigue, and heightened smell are common. Risk of miscarriage is highest here (~10–20% of known pregnancies).
- 2nd Trimester (Weeks 14–27): Most comfortable period. Anatomy scan around week 20 checks for structural abnormalities. Movements ("quickening") felt around 18–22 weeks.
- 3rd Trimester (Weeks 28–40): Rapid weight gain for both mother and baby. Lungs mature. Braxton Hicks contractions begin. At 37 weeks, the baby is considered "early term"; 39–40 is "full term".
Medical disclaimer: This calculator provides an estimate based on Naegele's Rule. Always confirm your due date with your midwife or OB-GYN using ultrasound dating, especially if your cycles are irregular.