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Pregnancy educational DVDs

Pregnancy takes approximately 40 weeks between the time of the last menstrual cycle and birth (38 weeks from fertilization). It is divided into three trimesters.

The first trimester carries the highest risk of miscarriage, the unintentional abortion of a fetus. It is often a result of defects in the fetus, its parent, or damage caused after conception.

Traditionally (according to Naegele's Rule), a human pregnancy is considered to last approximately 40 weeks (280 days) from the last menstrual period (LMP), or 38 weeks (266 days) from the date of conception.

However, a pregnancy is considered to have reached term between 38 and 42 weeks. Babies born before the 37 week mark are considered premature, while babies born after the 42 week mark are considered postmature.

However, the average length of pregnancy depends on ethnic background of the mother (Caucasian women are more likely to have a longer pregnancy than other women) and if it is a first pregnancy (which tend to last longer than subsequent pregnancies). For example, a Caucasian woman's first pregnancy lasts an average 274 days from conception (288 days from the last menstrual period).

An accurate date of conception is important, because it is used in calculating the results of various prenatal tests (for example, in the triple screen test).

A decision may be made to induce labour if a baby is perceived to be overdue. Due dates are only a rough estimate, and the process of accurately dating a pregnancy is complicated by the fact that not all women have 28 day menstrual cycles, or ovulate on the 14th day following their last menstrual period. Approximately 3.6% of all mothers deliver on the due date predicted by LMP, and only 4.7% give birth on the day predicted by ultrasound.