1 week of pregnancy: how to count terms? In modern obstetrics pregnancy countdown begins with the first day of the last menstrual period. Strange, you say, but at that day I have not been pregnant yet. So why do experts count terms in such a strange form? Absolutely right, this way of counting has been adopted as a basis because it is very difficult to determine the date of conception accurately, or at least the date of ovulation as far as it is a completely individual factor.

Of course, if you count your pregnancy by obstetric period, at the first week there is no baby inside, but at this time an ovum matures in a woman’s body . The unique process of ovulation occurs during each menstrual cycle due to the increase of concentration of progesterone and the fact that the egg is released from the ovary into the abdominal cavity and then into the fallopian tube, where the egg is expecting fertilization during the day. On this day the most chance of becoming pregnant is great.

At average cycle time of 28 days ovulation occurs on the 14th day, and if the fertilization has occurred on this day, it is from this point counted the real term of fetal pregnancy, when in the process of connection of male and female cells a new human appears.

That is why the difference between obstetric and fetal gestational age is in two weeks: it all depends on what is taken as a starting point.

If obstetric period of the 1st week of pregnancy starts from the first day of last menstrual period, the period of fetal pregnancy is counted directly from the day of conception.