- How long will your pregnancy last?
medical/nutritional history, and normality of menstrual cycle.
- Calculating the EDD (estimated due date). Here's a simple way to find you EDD (again, remember there is no accurate date; we say "estimated" because we can target only the most probable date). If you have a regular 28-day menstrual cycle, note the first day of your last period then add 7 days. Then count back 3 months. If your last period started on August 1, your estimated delivery date (if you count 3 months backward and add 7 days) is may 8 of the following year. Remember that this is only an estimation and much will depend on the regularity of your menstrual period. If your period is inconsistent, consult your OB-gyne.
- Listening to the fetal heart. A health care practitioner may help you determine your due date by listening to the sound of the baby's heartbeat. The heartbeat can be detected at about 18 to 20 weeks of pregnancy with the use of a stethoscope or a Droppler device. The heart becomes clearly discernible through the Droppler device when the fetus is around 10 to 12 weeks old. Take note that the fetal heart can usually be seen at around 6 weeks so the probable dates suggested here are the most appropriate time to estimate the fetal heart.
- Using Ultrasound. This is the most popular way to determine the due date and to give the parents an initial view of their baby. If you're not confident in the EDD, the doctor can do an ultrasound to investigate fetal development and growth without the harm of x-rays. The ultrasound estimates the age and size of the fetus by measuring the circumference of its head. An image of the fetus can be detected by a quartz crystal with high-frequency sound waves. The device is placed on the pregnant woman's abdomen and waves are beamed toward the fetus. The ultrasound can depict soft tissues in details; it provides a good picture of the growing fetus inside the womb.