From the Research
The expected date of delivery (EDD) based on a last menstrual period (LMP) of January 17,2025, is October 24,2025. This calculation follows Naegele's rule, which is the standard method used in obstetrics to estimate the delivery date. The formula adds 7 days to the first day of the last menstrual period, then adds 9 months, or alternatively counts forward 280 days from the LMP. Pregnancy typically lasts about 40 weeks (280 days) from the first day of the last menstrual period, although it's essential to understand that this is just an estimate. Only about 5% of women deliver exactly on their due date, with most delivering within a window of about two weeks before or after. Early ultrasound dating, especially in the first trimester, can provide a more accurate EDD if the date of the last menstrual period is uncertain or if menstrual cycles are irregular, as supported by studies such as 1. It's also important to note that the accuracy of LMP-based EDDs can be limited, and factors such as irregular menstrual cycles or uncertainty about the date of the last menstrual period can affect the accuracy of the estimated delivery date, as discussed in studies like 2 and 3. Therefore, while October 24,2025, is the calculated EDD based on the provided LMP, it's crucial to consider the potential for variation and the importance of early ultrasound dating for a more precise estimation. Key points to consider include:
- The use of Naegele's rule for estimating the EDD
- The potential for variation in the actual delivery date
- The importance of early ultrasound dating for accurate EDD estimation
- The limitations of LMP-based EDDs, especially in cases of irregular menstrual cycles or uncertainty about the LMP date, as highlighted in studies such as 4 and 5.