How to Use the Pregnancy Calculator

This tool helps you estimate your due date and track your pregnancy progress. Here’s a step-by-step guide:

Basic Usage

1. Enter at least one date in any of the available fields:
   • Last Menstrual Period (LMP)
   • Due Date
   • Ultrasound Date
   • Conception Date
   • IVF Transfer Date
2. Click the “Calculate” button
3. View your results which will appear below the form:
   • Estimated Due Date
   • Current Pregnancy Week
   • Pregnancy Status (whether you’re full-term)

Detailed Instructions for Each Input Option

1. Last Menstrual Period (LMP)

• Enter the first day of your last period
• The calculator adds 280 days (40 weeks) to estimate your due date
• This is the most common method for calculating due dates

2. Due Date

• If you already know your due date from a healthcare provider
• The calculator will show your current pregnancy progress based on this date

3. Ultrasound Date

• Enter the date you had an ultrasound that determined gestational age
• The calculator adjusts the due date based on typical ultrasound timing

4. Conception Date

• Enter the date you believe conception occurred
• The calculator adds 266 days (38 weeks) to estimate your due date

5. IVF Transfer Date

• For IVF pregnancies, enter your embryo transfer date
• The calculator adds 266 days (for Day 5 embryos) to estimate your due date

Understanding the Results

After clicking “Calculate”, you’ll see:

1. Estimated Due Date: The calculated or provided due date in a readable format
2. Current Pregnancy Week: How many weeks pregnant you are today
3. Pregnancy Status:
   • Not yet full-term: If you’re less than 37 weeks (shown in pink)
   • Full-term pregnancy: If you’re between 37-42 weeks (shown in green)
   • Past due date: If you’re more than 42 weeks (shown in pink)

Important Notes

• The calculator prioritizes dates in this order if you enter multiple:
  1. Due Date
  2. Ultrasound Date
  3. IVF Transfer Date
  4. Conception Date
  5. Last Menstrual Period
• Only about 4% of babies are born exactly on their due date
• Most babies are born within two weeks before or after the estimated due date
• Always consult with your healthcare provider about your specific pregnancy

Helpful Tips

• Click the “?” icons next to each field for explanations about that date type
• The calculator works best when you know at least one reliable date
• You can update the calculation anytime by changing a date and clicking “Calculate” again

This tool is designed to provide estimates based on standard medical calculations, but every pregnancy is unique. Use it as a guide alongside professional medical advice.

Frequently Asked Questions (FAQs) – Pregnancy Calculator

General Questions

1. How accurate is this pregnancy calculator?

The calculator provides estimates based on standard medical calculations:

• LMP method: ±2 weeks accuracy
• Ultrasound dating (first trimester): ±5-7 days accuracy
• Conception/IVF dating: ±3 days accuracy
  Remember only about 4% of babies are born exactly on their due date.

2. Which date should I enter for the most accurate results?

Accuracy priority:

1. IVF transfer date (most accurate)
2. Early ultrasound date (especially first trimester)
3. Known conception date
4. Last menstrual period (LMP)

3. Why does my doctor’s due date differ slightly?

Healthcare providers may adjust dates based on:

• Ultrasound measurements
• Irregular cycles
• IVF embryo age (Day 3 vs Day 5)
• Clinical judgment

Calculation Methods

4. How is the due date calculated from LMP?

Standard calculation:

• Add 280 days (40 weeks) to first day of last period
• Assumes 28-day cycle with ovulation on day 14

5. How does IVF dating work?

For IVF pregnancies:

• Day 5 embryos: Add 266 days (38 weeks) to transfer date
• Day 3 embryos: Add 268 days (38 weeks + 2 days)

6. How does conception dating work?

• Add 266 days (38 weeks) to conception date
• Typically assumes conception occurred 14 days after LMP

Technical Questions

7. What if I have irregular periods?

The LMP method may be less accurate if you have:

• Cycles longer than 28 days
• Irregular ovulation
• Recent hormonal contraception use
  In these cases, ultrasound dating is more reliable.

8. How is pregnancy week calculated?

Weeks are counted as:

• Completed weeks + days (e.g., 12 weeks 3 days)
• Based on days passed since LMP/conception
• 40 weeks = full term pregnancy

9. What defines “full-term” pregnancy?

Medical definitions:

• Early term: 37 weeks 0 days to 38 weeks 6 days
• Full term: 39 weeks 0 days to 40 weeks 6 days
• Late term: 41 weeks 0 days to 41 weeks 6 days
• Post term: 42 weeks and beyond

Troubleshooting

10. Why won’t the calculator give me results?

Common issues:

• No date entered (need at least one date)
• Invalid date format (use calendar picker)
• Future dates where appropriate
• Browser JavaScript disabled

11. Can I use this for twins/multiples?

The calculator works for multiples but:

• Twins often deliver 36-37 weeks
• Triplets often deliver 32-34 weeks
  Consult your doctor for multiple-specific dating.

12. What if I don’t know any exact dates?

Options:

• Estimate LMP as best you can
• Wait for first ultrasound dating
• Use our reverse calculator (enter due date to find conception period)

Medical Questions

13. Should I change my plans based on this calculator?

Always consult your healthcare provider about:

• Medical decisions
• Delivery planning
• Pregnancy concerns
  This tool is for informational purposes only.

14. Why does my pregnancy app show different weeks?

Differences may come from:

• Calculation methods (LMP vs ultrasound)
• Rounding conventions
• Different term definitions
• App-specific algorithms

15. When should I contact my doctor about my due date?

Contact your provider if:

• Your dates differ by >5 days from ultrasound
• You have pregnancy concerns
• You reach 41 weeks without labor signs
• You notice reduced fetal movement

For the most accurate pregnancy dating, early ultrasound (especially first trimester) combined with clinical assessment provides the best estimates. This calculator is designed to complement, not replace, professional medical care.