1stPregnant.com deals with all facets of information about pregnancy in female humans. This website does not deal with any other aspect of pregnancy such as animals (non humans) etc.

Pregnancy can be defined as the female carrying one or more offspring, referred to as a fetus or embryo, inside their uterus. Multiple fetuses / embryo are how twins, triplets, or more are born. Technically speaking, the term embryo is used to describe the developing offspring during the first eight weeks following conception, and the term fetus is used from about two months of development until birth.

Often, human pregnancy is arbitrarily divided into three trimester periods. These three divisions reference the different stages of prenatal development.

During the first trimester is when the highest risk of a miscarriage, the act of natural death or embryo or fetus. Within the second trimester is the ability to monitor and diagnosed of the fetus. At the start of the third trimester the fetus can be evaluated for the ability to survive with or without medical help outside the uterus.

Estimating the date of birth is done in several easy calculations. An expected delivery date (EDD) is calculated at 40 weeks counting from the last menstrual period (LMP). Another way to calculate an expected delivery date is 38 weeks from the day of conception.

 More complicated methods of determining expected delivery date is available and they take into consideration such items as if this is your first child, ethnicity, length of menstrual cycle, menstrual regularity, parental age, weather and many other items.

When the pregnancy has attained 37 complete weeks, but is less than 42 weeks, it is referred to as “at term.” The time prior to 37 weeks, 259 days, is referred to as pre-term and from week 42, 294 days, the term is called post-term and this is when there are elevated risks for mother and fetus are significant.

Commonly, obstetricians prefer to induce labor in a non complicated pregnancy at some time between 41 and 42 weeks.

Whichever calculation you prefer to use, the average number of births on the expected delivery date is less than 5%. On average, 50% of births occur within a week of expected delivery date and 90% of births occur within two weeks of expected delivery date.

Please remember, pre and post terms are used to calculate time of pregnancy, and the terms premature and postmature have historical meanings and relate more to the size of the infant and their development.