Why dates may not match
Irregular cycles, early or late ovulation, uncertain period dates, and the timing of ultrasound measurements can make ultrasound dating and LMP dating differ.
- Early ultrasound may be more useful for pregnancy dating.
- Long cycles or later ovulation can make LMP dating look too far along.
- Your provider should decide whether to adjust the official due date.
Medical note
If your provider has assigned an official due date, use that record for care planning. This tool only helps organize the difference.