GUIDE深度 · Deep dive
Ways to Estimate a Due Date
The common method is LMP plus 280 days (Naegele). Adjust for non-28-day cycles; with a known conception date use plus 266 days; first-trimester ultrasound (CRL) is most accurate. Methods differ by a few days, and clinicians pick one as the official due date.
LMP plus 280 days, adjusted one day per cycle day.
Conception date plus 266 days.
First-trimester ultrasound by crown-rump length.
Early ultrasound usually takes precedence.
For ART, use transfer/retrieval dates.
FAQ
Why one day off from an app?
Cycle adjustment, time zones or algorithms differ; use the clinician's date.
Will I deliver at 40 weeks?
No; 37-42 weeks is common, and post-42 needs assessment.