Pregnancy refers to the period in female reproductive development from conception to birth. This period usually lasts for 40 weeks, but completion of 37 weeks of pregnancy is considered a full-term pregnancy. Preterm is defined as prior to 37 weeks’ gestation. Pregnancy is divided into three trimesters: first trimester 1–12 weeks, second 13–28 weeks, and third trimester is from 29–40 weeks of gestation. Pregnancy includes implantation of the embryo, growth and development of the fetus, and the growth of the placenta.

During this time, a healthy pregnancy allows a fetus to develop from the single fertilized cell, the zygote, into a complex of approximately 200 billion cells at birth. The neonate is born already organized into the major anatomical structures, central nervous system, and interacting biological ...

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