Six tools and no newsletter wall

birthdate.baby exists because pregnancy advice online is written for nobody in particular. A due date is the one piece of information that makes it specific, so this site asks for that and nothing else.

What it does

Six free tools. A due date calculator that works from your last period, a known conception date, an IVF transfer or a dating scan. Forty two week by week pages. A hospital bag checklist that knows whether you are early or late. A contraction timer. A gear list sorted by the week to buy rather than by category. And the Chinese gender chart, which is folklore and is labelled as such.

All of them work fully without an email address. Nothing is held back behind a form and there is no account to make.

Where the numbers come from

Dating uses the standard 280 day count from the first day of the last menstrual period, adjusted for cycle length, which is what obstetric practice uses everywhere. Conception dating is 266 days. IVF dating is 280 days minus fourteen minus the age of the embryo at transfer, so a day 5 blastocyst is 261 days. Ultrasound dating fixes gestational age directly from the scan.

Scan and screening windows are the standard ones: nuchal translucency at 12w3d to 13w3d, anatomy at 18 to 20 weeks, glucose screening at 24 to 28 weeks, Tdap at 27 to 36 weeks, group B strep at 36 to 37 weeks. Sizes and weights on the week pages are typical averages, crown to rump through week 20 and crown to heel from week 21.

The arithmetic is covered by a test suite that pins every mode against hand computed dates, including leap years and daylight saving boundaries, because a confidently wrong due date is worse than no calculator.

What it does not do

It does not know anything about you or your pregnancy. It cannot tell you whether anything is normal, whether a date should be revised, or what a symptom means. It is careful arithmetic on a calendar and a set of checklists. Everything else is a conversation with your midwife or doctor.

Your data

Your date is stored in your own browser and is never sent anywhere. Ticked checkboxes and timed contractions are the same. If you type an email address into a signup form, that address is sent to us and nothing else is. There is more detail on the privacy page.

How it pays for itself

Some links to shops. That is the whole model, it is set out plainly on the disclosure page, and it does not change what the tools say.

Contact

Corrections are welcome, particularly to the maths. Write to [email protected].