Question 1

How is my due date calculated?

Accepted Answer

Due date is calculated using Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day cycle. For different cycle lengths, the due date is adjusted accordingly. For example, a 30-day cycle adds 2 extra days to the due date.

- Standard formula: LMP + 280 days = estimated due date (EDD)
- For a 30-day cycle, add 282 days; for a 26-day cycle, add 278 days
- IVF patients: add 266 days from egg retrieval date for the most accurate EDD
- First-trimester ultrasound (weeks 8–12) can adjust the EDD to within 5–7 days

Question 2

How accurate is a due date calculator?

Accepted Answer

Only about 4-5% of babies are born on their exact due date. Most babies (80%) are born within 2 weeks of the due date, between 38-42 weeks. An ultrasound in the first trimester can provide a more accurate estimate, typically within 5-7 days.

- Only 4–5% of babies arrive on the exact due date
- 80% of babies are born between 38 and 42 weeks (within 2 weeks of EDD)
- First-time mothers tend to deliver 3–5 days after their due date on average
- First-trimester ultrasound dating is accurate to ±5–7 days
- Second-trimester ultrasound accuracy drops to ±10–14 days

Question 3

What are the three trimesters of pregnancy?

Accepted Answer

First trimester: Weeks 1-12 (critical development period). Second trimester: Weeks 13-26 (baby grows rapidly, you may feel movement). Third trimester: Weeks 27-40 (baby gains weight, prepares for birth). Each trimester has different symptoms and developmental milestones.

- First trimester (weeks 1–12): organs form, heartbeat detectable by week 6, morning sickness peaks weeks 8–10
- Second trimester (weeks 13–26): gender visible by week 18–20, first kicks felt around week 16–22
- Third trimester (weeks 27–40): baby gains ~0.5 lb/week, lungs mature by week 36
- Viability milestone: week 24 – survival rate outside the womb reaches 50–70%
- Week 37+: baby is considered early term; week 39–40 is full term

Question 4

When should I see a doctor after finding out I'm pregnant?

Accepted Answer

Schedule your first prenatal visit around weeks 8-10. Contact your doctor sooner if you have bleeding, severe pain, or a history of complications. Early prenatal care is important for monitoring baby's development and your health.

- First prenatal visit (weeks 8–10): blood work, medical history, initial ultrasound
- Start taking 400–800 mcg folic acid daily as soon as you suspect pregnancy
- Call your doctor immediately if you experience heavy bleeding, severe cramping, or fever
- Most women have 10–15 prenatal visits total across the full pregnancy
- High-risk pregnancies (age 35+, multiples, diabetes) require more frequent monitoring

Question 5

What is full term pregnancy?

Accepted Answer

Full term is 39-40 weeks. Early term is 37-38 weeks, late term is 41 weeks, and post-term is 42+ weeks. Babies born at 37+ weeks are generally healthy, but 39+ weeks is ideal for full lung and brain development.

- Early term (37–38 weeks): baby is healthy but brain grows 35% more between weeks 37–39
- Full term (39–40 weeks): ideal for delivery – lungs and brain are fully mature
- Late term (41 weeks): doctor may discuss induction – placenta efficiency begins to decline
- Post-term (42+ weeks): induction is typically recommended to reduce complications
- Average first pregnancy lasts 40 weeks + 5 days; subsequent pregnancies average 40 weeks + 3 days

Question 6

How do I calculate due date from conception?

Accepted Answer

Add 266 days (38 weeks) to your conception date. Since conception usually occurs about 14 days after LMP, this gives the same result as the LMP method. If you know your exact conception date (from IVF), this method may be more accurate.

- Conception date + 266 days = estimated due date
- Conception typically occurs 12–16 days after the first day of LMP (average 14 days)
- IVF patients know the exact conception date, making this method most accurate for them
- Ovulation test kits (LH surge detection) can pinpoint conception to within 24–36 hours

Due Date Calculator

Calculate From

Last Menstrual Period

Trimester Timeline

Key Pregnancy Milestones (2/10 reached)

Example Calculations

1Calculate from LMP (28-Day Cycle)

2Calculate from Conception Date

Frequently Asked Questions

How is my due date calculated?

How accurate is a due date calculator?

What are the three trimesters of pregnancy?

When should I see a doctor after finding out I'm pregnant?

What is full term pregnancy?

How do I calculate due date from conception?

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