About BabyAwaits
Pregnancy is forty weeks of waiting, wondering, and Googling at 2 a.m. BabyAwaits exists so the numbers you meet on that journey — due dates, fertile windows, weights, weeks — are clear, honest, and calculated the same way your care team calculates them.
Our methodology
Due dates: Naegele's rule (280 days from the first day of the last period), adjusted for cycle length; 266 days from conception; or 261/263 days from a day-5/day-3 IVF transfer. These are the standard formulas of US obstetric care.
Ovulation: ovulation day estimated as cycle length minus luteal phase (14 days for most), with a fertile window of the five days before through the day after ovulation, reflecting sperm and egg survival times.
Fetal size: weekly averages in line with the growth charts used in US prenatal care — crown-rump length through week 19, crown-heel from week 20. Fruit comparisons are friendly approximations, not clinical data.
Weight gain ranges: the Institute of Medicine (National Academy of Medicine) 2009 guidelines, still the standard in US practice — including the twin ranges.
Implantation: the 6-12 day window (most commonly days 8-9) is from Wilcox, Baird & Weinberg, New England Journal of Medicine, 1999 — the landmark study that measured implantation directly.
hCG trends: the classic doubling-every-48-72-hours rule and the 35%-minimum-rise-per-48-hours threshold (Barnhart et al., 2004). We compute your numbers; interpretation stays with your provider.
Kick counting: the count-to-10-within-two-hours method as described in ACOG patient guidance on fetal movement in the third trimester.
Growth percentiles: CDC / National Center for Health Statistics growth-chart LMS tables for birth-24 months (the WHO-derived charts), computed with the CDC's documented z-score formula. Where we could not verify a complete official dataset — head circumference, for now — we simply don't publish the feature.
Baby names: U.S. Social Security Administration national name statistics (public domain), loaded in full for the latest published year, with decade trends since 1984 for recent top-500 names.
Editorial standards
Week-by-week content is written from established, widely accepted obstetric knowledge and public-health patient education (such as ACOG and CDC materials), and is reviewed periodically. We deliberately avoid alarming framing: most variation in pregnancy is normal, and these pages say so.
Medical disclaimer: BabyAwaits offers education and general information, not medical advice, diagnosis or treatment. Always consult a qualified provider about your specific situation, and never delay care because of anything read here.
The privacy promise
Every calculator on this site runs entirely in your browser. Dates and logs you enter are stored only in your own device's browser storage — clear them anytime by clearing site data. We never receive, see or store them. See the privacy policy for details, including how advertising cookies work.
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