The human gestation period of approximately 40 weeks between the time of the last menstrual cycle and delivery is traditionally divided into three periods of three months, or trimesters. A pregnant woman Pregnancy is the process by which a mammalian female carries a live offspring from conception until it develops to the point where the offspring is capable of living outside the womb. ... The phrase menstrual cycle ( or period) refers to the recurring physiological changes in a females body that are under the control of the reproductive hormone system and necessary for reproduction. ... Newborn with suctioning and umbilical cord Childbirth (also called labour, birth, or parturition) is the culmination of pregnancy, the emergence of a child from its mothers uterus. ...
In the first trimester the embryo undergoes most of its early structural development. Most miscarriages occur during this period.
In the second trimester the embryo, now known as a fetus, is recognisable as human in form, but is not developed enough to be viable if born.
In the third trimester the fetus reaches viability, and may survive if born prematurely.
The use of modern medical intensive care technology has greatly increased the probability of premature babies living, and has pushed back the boundary of viability to much earlier dates than would be possible without intensive medical assistance. In spite of these developments, premature birth remains a major threat to the fetus, and may result in ill-health in later life, even if the fetus survives the birth and subsequent intensive care. Embryos (and one tadpole) of the wrinkled frog (Rana rugosa you beezie). ... Miscarriage is the lay term for the natural or accidental termination of a pregnancy at a stage where the embryo or the fetus is incapable of surviving. ... Fetus at eight weeks A fetus (alternatively foetus or fœtus) is an unborn human offspring from the end of the 8th week of pregnancy (when the major structures have formed) until birth. ... Viability can mean: In an environmental conservation context, viability indicates the ability of a conservation target to persist for many generations or over long time periods. ... Intensive care medicine or critical care medicine is concerned with providing greater than ordinary medical care and observation to people in a critical or unstable condition. ... Premature birth (also known as preterm birth) is defined medically as birth occurring earlier than 37 completed weeks of gestation. ...
The actual boundaries of when an embryo is regarded as a fetus or a fetus becomes regarded as potentially viable depend on the definitions of these terms, and do not necessarily fit neatly on the classic trimester boundaries. Note also that these boundaries are the matter of both medical and political controversy.
Some timings that have been used are:
embryo to fetus: eight weeks
the edge of viability: 22 - 25 weeks (note the risk of death or disability, see the reference cited below).
Nevertheless, the concept of pregnancy as divided into three trimesters continues to be used in practical healthcare.
A pregnant woman Human pregnancy is the part of the life reproduction process in which a human female carries a live offspring from implantation until childbirth. ...
Trimester: The nine months of pregnancy is traditionally divided into three trimesters: distinct periods of roughly three months in which different phases of fetal development take place.
The third trimester marks the final stage of fetal growth, in which systems are completed, fat accumulates under the soon- to-be-born baby's skin, and the fetus at last moves into position for birth.
Trimester is thus related in origin to menses and menstruation.
In the second trimester the embryo, now known as a fetus, is recognisable as human in form, but is not developed enough to be viable if born.
In the third trimester the fetus reaches viability, and may survive if born prematurely.
The use of modern medical intensive care technology has greatly increased the probability of premature babies living, and has pushed back the boundary of viability to much earlier dates than would be possible without intensive medical assistance.
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