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Chapter 5: Prenatal Development. Section 5-1: The Developing Baby. During pregnancy, a single cell grows and develops into a human being capable of independent life. This amazing process, which takes about nine months, is called prenatal development . Conception.
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Section 5-1: The Developing Baby During pregnancy, a single cell grows and develops into a human being capable of independent life. This amazing process, which takes about nine months, is called prenatal development.
Conception • Once a month an ovum – a female cell or egg – is released by one of a woman’s ovaries. • The egg moves through the Fallopian tube to the uterus, the organ in a woman’s body in which a baby develops during pregnancy. • This journey takes about 2 or 3 days.
Conception • When the egg reaches the uterus, it usually dissolves and is flushed out of the body with the menstrual flow. • Sometimes, a egg meets and is fertilized by a sperm, or male cell. • When the ovum and sperm unite, conception takes place, and pregnancy begins.
Conception • An ovum lives 12 to 24 hours, while sperm is capable of fertilizing an ovum for 48 to 72 hours. • There are 3-4 days in each woman’s cycle during which intercourse could lead to conception.
Stages of Development • The baby’s development is often grouped into three stages: • Zygote • Embryo • Fetus
Period of the Zygote • The first stage in development is the period of the zygote, or fertilized egg. • This period lasts about 2 weeks. • In this period, the zygote travels down the Fallopian tube and attaches itself to the thickened lining of the uterus. • From the uterus, the zygote draws nourishment from the mother’s body.
Period of the Zygote • The zygote grows by cell division. • The single, complete cell divides and becomes two. • Then those two cells spilt to become 4 and so on. This process continues to form a mass of cells. • Despite the rate of growth, after two weeks, the zygote is only the size of a pinhead.
Period of the Embryo • The second stage of pregnancy is the period of the embryo. • The embryo is the developing baby from about the third to the eighth week of pregnancy. • During this time, the embryo grows rapidly. • Several important and amazing changes occur during this period.
Period of the Embryo • First change: the mass of cells develops into all the major systems of the human body – heart and lungs, and bones and muscle. • Even though these systems begin to develop this early, they are no where near being ready to function. • Even though the brain is not fully developed or fully functioning, it begins to take control of these body systems at this early stage. • Brain development can be seriously harmed by drugs or alcohol – it is extremely important for pregnant women to avoid these substances.
Period of the Embryo • Second change: a sac filled with fluid forms around the embryo. • This amniotic fluid protects the developing baby. • It cushions the embryo from any bumps or falls that the mother might have.
Period of the Embryo • Third change: a tissue called the placenta develops. • The placenta is very rich in blood vessels. • The mother’s blood stream carries food and oxygen to the placenta. • From there, it reaches the baby through the umbilical cord.
Period of the Embryo • Fourth change: the umbilical cord • The umbilical cord brings nourishment to the baby and takes waste products away. • The umbilical cord is generally not flexible enough to loop around the fetus although this may occur in rare cases. • Only after the baby is born does the umbilical cord become limp.
Period of the Fetus • Third and final stage of pregnancy. • Begins about the 8th or 9th week and lasts until birth. • Fetus: the name for the unborn baby from the 8th/9th week until birth.
Period of the Fetus • Around the 4th or 5th month you may be able to feel the fetus kicking or moving. • At first the movements are soft and don’t happen a lot but they gradually become stronger and more frequent. • A doctor may ask when these movements were first felt – this could help them get a better estimate of the baby’s age and a more accurate idea of the due date.
Period of the Fetus • As the fetus grows, so does the amount of the surrounding amniotic fluid. The uterus expands, too, and the woman’s abdomen grows. • Just before delivery, the amount of amniotic fluid decreases. • When the fetus grows large, it no longer has the room to stretch out and curls up into what is called the fetal position.
Period of the Fetus • By the 7th month the fetus is capable of living outside the uterus – but not without a great deal of medical help. • In the last few months of pregnancy the fetus becomes ready to live independently. • The body’s major organs become ready to function without help from the mother’s body.
Period of the Fetus • Also in the last few months, the fetus will rapidly gain weight. • Fat deposits, which will help the baby maintain body heat after birth, are added under the skin. • The fetus, which had been thin and wrinkled, takes on the smoother, rounder appearance of a baby.
Period of the Fetus • During these final weeks, the fetus also stores nutrients and builds immunity to diseases and infections. • The fetus can do a surprising number of things – suck its thumb, cough, sneeze, yawn, kick, and hiccup. A baby can even cry before birth.
Losing a Baby • If a developing baby dies before 20 weeks of pregnancy it is called a miscarriage. • If it occurs after 20 weeks, it is called a still birth.
Losing a Baby • The loss of a baby can be a huge shock and bring great pain. • Parents often feel as if they lost a baby that had been born – they must go through the same stages of grief as anyone who has lost a family member • About 20% of all pregnancies end in misscarriage.
