Chapter 3: Prenatal Development + Birth:
What are the periods of prenatal development, and what are major milestones within
each period?
Germinal Period: The period of prenatal development that takes place in the first two weeks after conception.
Includes the creation of the zygote (fertilized egg + sperm), continued cell division, and attachment of the zygote to the uterine wall.
The zygote spends the next few days traveling down the fallopian tube. During this time, it divides to form a ball of cells called a blastocyst.
The blastocyst is made up of an inner group of cells with an outer shell.
The inner group of cells will become the embryo, eventually develops into fetus than baby
The outer group of cells called trophoblast will become structures, called membranes, which nourish and protect the embryo.
Just one week after conception, cells of the blastocyst have already begun specializing. The germinal period ends when the blastocyst attaches to the uterine wall.
Embryonic Period: The period of prenatal development that occurs two to eight weeks after conception.
Rate of cell differentiation intensifies, support systems for the cells form, and organs appear.
Highest Risk
As many as 1 in 4 pregnancies end in miscarriage, with most occurring in the first trimester.
Miscarriage, or more formally called spontaneous abortion, is the expulsion from the uterus of an embryo or fetus that is unable to survive outside the womb.
Severely defective embryos usually do not survive beyond the first trimester, or 3-month period, of pregnancy.
If occurs after 20 weeks is referred to as stillbirth.
Miscarriage for someone who is trying to conceive can cause increased anxiety for individual and/or their partner
Clinicians should be aware and refer to counseling and support services as appropriate
The Fetal Period: the prenatal period of development that begins after Two months and lasts for seven months on average
Dramatic growth occurs in prenatal size and weight
Fingers, toes, skin, features, lungs, other structures, and reflexes all develop to prepare for birth
The fetal period marks a critical stage during which the baby-to-be becomes responsive to its environment in new ways and is developmentally influenced by factors both inside and outside the uterus
What is a teratogen? When and why are teratogens more likely to have an effect?:
Environmental agents, such as a virus, a drug, or radiation, that can interfere with normal prenatal development and cause developmental abnormalities
Maternal Influences: Understand how the following affect fetal development:
nutrition
stress
illness
environmental exposures
What is the birth process?
a) First stage: cervix is dilating;
(b) late first stage (transition stage): cervix is fully dilated and the amniotic sac has ruptured, releasing amniotic fluid;
(c) second stage: birth of the infant;
(d) third stage: delivery of the placenta (afterbirth).
First stage: uterine contractions (12 to 14 hours) Contractions cause the cervix to stretch and open. Amniotic sac ruptures, releasing amniotic fluid
Second stage: delivery (45 minutes to an hour) Baby begins moving out of the uterus. Stage ends at the birth of the infant
Third stage: afterbirth (a few minutes) Placenta, umbilical cord, and other membranes
are detached and expelled from the uterus
*** The norm for first births is about 14 hours.
At the beginning of labor, contractions come 15 to 20 minutes apart and last anywhere from 15 to 60 seconds.
The typical method of childbirth is vaginal delivery. However, cesarean delivery is also used.
Cesarean delivery is the delivery of a baby by surgical removal from the uterus.
Cesareans are commonly performed when labor progresses too slowly and/or when the fetus seems to be in distress
Terms to Know:
Teratogen
Fetal viability
Low birth weight
Apgar scale: Baby is given a score of 0,1, or 2 twice at 1st minute of life then again at 5
minutes each time these scores are compared to deal score o 10( which is rarely
attained). If Apgar score is 7 or higher, all is good
APGAR: appearance, pulse, grimace, activity, respiration