Pregancy calculator and estimated due date

How does a pregnancy calculator work?

Through your last period's date, the pregnancy calculator will make an estimate of your due date. It can be confusing for future mothers, but the medical reference to find out the expected date of delivery is from the date of the last period, which is called the LMP. Even though ovulation happens 14 days after the first day of the cycle, as it is difficult to know when fertilization happened, the medical community uses as the beginning of pregnancy the first day of the last period's cycle.

How long does a pregnancy last?

A pregnancy lasts for 40 weeks or 280 days. From the 37th week of pregnancy, the baby can already be born, but a woman can have a pregnancy of up to 42 weeks. Between 41 and 42 weeks, if the baby is not born, the doctor will decide what is the best approach. For mothers who want to have an elective cesarean section, it can be done after the 39th week.

How do we calculate your due date?

In order to find out your Estimated Due Date (EDD), we use the Naegele's Rule which is the standardised way to calculate the due date (EDD) from the date of the last menstrual period (LMP). The rule was created by German Obstetrician Franz Karl Naegele, hence the name Naegele's Rule.

To arrive at the Estimated Due Date, we add 280 days to the first day of the last menstrual period. From the resulting date, we know that it can fall a few days before or after. It is estimated that only 5% of babies are born on the estimated date. We consider a standard 28-day cycle. If your cycle is longer or shorter, we make an adjustment with the difference in days.

What If I don't know the date of my last period?

Many women don't remember the date of their last period or have irregular cycles, so knowing your LMP may not be easy. In this situation, the best thing to do is to have an ultrasound. This way, the doctor will be able to tell the size of the embryo or gestational sac, and will be able to tell the mother the estimated due date, known as the EDD.

Why is pregnancy counted in weeks and not in months?

Since your baby's development in the first 3 months is very rapid, counting by weeks instead of months allows for much more efficient monitoring than monthly. Furthermore, since each month has a different number of days, then counting by week, 7 days, makes it easier.

How many months am I pregnant?

It may be strange in a conversation with relatives and friends to use weeks instead of months, since we are so used to referring to a 9-month pregnancy. To find out how many months you are, you can use the table below.