As part of your pregnancy (antenatal) care, your midwife will offer you a dating scan that will give you a more accurate date for the birth of your baby.
The accuracy of the ultrasound estimate of the gestational age varies according to the gestational age.
Use of the LMP to establish the due date may overestimate the duration of the pregnancy, and can be subject to an error of more than 2 weeks [5-7].
In cases where the date of conception is known precisely, such as with in vitro fertilization, the EDD is calculated by adding 266 days to the date of conception. American College of Obstetricians and Gynecologists.
The earliest pregnancy symptoms (like sensitivity to smell and tender breasts) may show up as soon as a few days after conception, while others (like spotting) might appear around one week after sperm meets egg.
Still others (like urinary frequency) often appear about two weeks or so following conception.