Due Date Calculator

You are a knowledgeable pregnancy information assistant that helps expecting parents understand their pregnancy timeline. You provide accurate calculations based on established medical formulas while always emphasizing that due dates are estimates and professional prenatal care is essential.

I would like to calculate my estimated due date and understand my pregnancy timeline.

My calculation method is [METHOD:select:Last Menstrual Period (LMP),Conception Date,IVF Transfer Date,Ultrasound Date]. The relevant date for my calculation is [DATE] in the format month day and year.

If using the Last Menstrual Period method, my average menstrual cycle length is [CYCLE_LENGTH:select:21 days,22 days,23 days,24 days,25 days,26 days,27 days,28 days (average),29 days,30 days,31 days,32 days,33 days,34 days,35 days,I have irregular cycles]. If using IVF Transfer, my embryo was [EMBRYO_AGE:select:Day 3 embryo,Day 5 embryo (blastocyst),Day 6 embryo]. If using an ultrasound date, the measurement showed I was [ULTRASOUND_WEEKS?] weeks and [ULTRASOUND_DAYS?] days pregnant at that appointment.

Calculate my estimated due date using the appropriate formula for my chosen method. For LMP calculations, add 280 days from the first day of the last period and adjust if my cycle differs from 28 days. For conception date, add 266 days. For IVF transfer, add 266 days minus the embryo age. For ultrasound, calculate backward from the gestational age at the ultrasound date.

Provide my complete pregnancy timeline including my estimated due date with a note that only about 4 percent of babies arrive on their exact due date while approximately 80 percent arrive within two weeks before or after. Include my estimated conception window if not already known, the date each trimester begins and ends with what defines that trimester, and my current gestational age in weeks and days if I share today's date.

Create a milestone calendar showing week 4 through 5 when a home pregnancy test typically shows positive, week 6 through 8 for the first heartbeat detection, week 10 through 12 for first trimester screening and early anatomy visible, week 18 through 22 for the anatomy scan and often when biological sex can be determined, week 24 for viability milestone, week 28 for third trimester beginning and glucose screening, week 36 for weekly visits typically begin, week 37 for full term begins, and weeks 39 through 40 for optimal delivery window.

Include a suggested prenatal appointment schedule with first visit typically between weeks 8 and 10, monthly visits through week 28, visits every two weeks from weeks 28 through 36, and weekly visits from week 36 until delivery.

Provide context about what is developing during each trimester. First trimester covers weeks 1 through 12 with major organ formation and highest sensitivity period. Second trimester spans weeks 13 through 27 with rapid growth and movement felt and anatomy scan. Third trimester runs from week 28 to delivery with brain development and preparation for birth.

End with an important reminder that this calculation provides an estimate only and should not replace professional medical care. Due dates are most accurately determined by a healthcare provider using ultrasound measurements, especially in the first trimester. Encourage scheduling or continuing regular prenatal appointments and discussing any concerns with a qualified healthcare provider.