A woman can estimate her due date with an ultrasound, by measuring the size of the uterus or by determining the first day of her last menstrual cycle, states WebMD. The average pregnancy due date falls 40 weeks after the first day of the woman’s last menstrual cycle.
Most women can get a general estimate on their due dates without visiting a doctor, according to WebMD. The easiest way to do this is to take the first day of the pregnant woman’s last menstrual period, add seven days to this date and then count backwards by three months. Women who know the exact day of conception can add 40 weeks to this date to find their estimated due date.
For a more accurate estimated due date, pregnant women can visit their doctors for additional tests, WebMD advises. A doctor can palpate around the pelvis to determine the size of the uterus. After 12 weeks, most doctors can determine how far along the pregnancy is and give a pregnant woman an estimated due date.
The most accurate doctor-administered tool for determining a woman’s due date is an ultrasound, states WebMD. This tool uses sound waves to create a computerized image of the fetus used to determine the size and age of the unborn baby. This provides doctors with an accurate assessment of the age of the fetus and when the delivery date can be expected. Most pregnant women deliver within two weeks of the doctor-estimated due date.