When a woman discovers that she is pregnant, one of the firsts things she wants to know is the pregnancy due date. Because a regular pregnancy period can be anywhere from 37 to 42 weeks, no one can give an exact due date. However, there are methods of calculating an approximate due date so that expectant mothers can make plans and record their pregnancy week by week.

Most experts say that the best way to determine a pregnancy due date is by doing an ultrasound during the first trimester. Ultrasound can be used to examine the development of the fetus, and then one will determine his or hers age based on which systems are entirely developed. The size of the baby is measured to see if it matches up with the last menstrual period. If an ultrasound is given during the first trimester, it can determine the age of the fetus within about 3 to 5 days. An ultrasound performed later in a pregnancy tends to be less accurate. As well, the fetal heartbeat can be used to determine the date of conception. The fetal heartbeat can be heard through Doppler beginning at 9 to 12 weeks.

The most common method of determining the pregnancy due date is by determining the first day of the last menstrual period. By adding 280 days to the last menstrual period, an expectant mother will have her approximate due date. It is important to be aware that this calculation is based on the assumption that a woman has her period every 28 days. Some women will have longer or shorter periods so the due date is considered an approximate date. As well, other factors that influence a pregnancy due date include: prenatal diet, weight, ethnicity, age of the mother, smoking, any prior pregnancies, ethnicity…etc. By the time a woman reaches her 40th week of pregnancy, she will receive weekly tests to make sure the baby is not in distress.

The standard equation for determining a pregnancy due date is: (Last Menstrual Period + 7 days) – 3 months = Expected Date of Delivery

Because determining the pregnancy due date is not an exact science, experts recommend that an expectant mother gets ready for birth two weeks before her due date. In any event, an expectant mother should relax and enjoy her pregnancy week by week.

This entry was posted on Monday, January 10th, 2011 at 8:13 am and is filed under Pregnancy. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.