• Prenatal Development
– Development that occurs between the moment of conception and the beginning of the birth process
• Development occurs in the mother’s uterus and the degree of safety depends on:
– (1) Mother’s age
– (2) Health
– (3) Food quality
– (4) Drug Intake
– (5) Chemical/Environ. Exposure
• Human growth occurs more rapidly during the prenatal period than any other period of human development
• Development begins in the fallopian tube when a sperm penetrates the wall of an ovum…This union forms a
• Gestational Period (266 days)
– From conception (zygote) to readiness for birth
(fetus of some 200 billion cells)
Germinal (zygote) Period
– Lasting from conception until the developing organism becomes firmly attached to the wall of the uterus
– Lasting from the 3 rd through the 8 th prenatal week. During which the major organs and anatomical structures take shape
– Lasting from the 9 th prenatal week until birth. During this period, all major organ systems begin to function and the fetus grows rapidly
• While traveling down the fallopian tubes towards the uterus, cell division occurs thru
• Continued cell division (60 to 80 cells) eventually forms a
. Generally occurs within 4 days of conception.
• As a result of continued cell differentiation
– The inner layer of the blastocyst (embryonic disk) becomes the embryo
– The outer layer of cells develops into tissues that protect and nourish the embryo
• The Blastocyst approaches the uterus (6 to 10 days) and attaches itself to the wall of the uterus thru small burr like tendrils which tap into the mother’s blood supply.
– Only about half of all fertilized ova are firmly implanted.
– Half of those that firmly implant are genetically abnormal, fail to develop, or implant in an area that is not conducive.
Resulting in miscarriages.
– 3 out of 4 zygotes fail to survive the initial stage of prenatal development.
DEVELOPMENT OF SUPPORT SYSTEMS
• Once implanted, the blastocyst’s outer layer rapidly forms 4 major support structures that protect and nourish the organism
—a watertight membrane that surrounds the developing embryo, serving to regulate its temperature and to cushion it against injuries
—surrounds the amnion and eventually becomes the lining of the placenta
—an organ formed from the lining of the uterus and the chorion, that provides for respiration and nourishment of the unborn child and the elimination of its metabolic waste
—a soft tube containing blood vessels that connects the embryo to the placenta
• The embryonic disk differentiates into 3 cell layers:
—outer layer which becomes the nervous system, skin, hair
—middle layer which becomes muscle, bones, circulatory system
—inner layer which becomes digestive, lungs, urinary tract, vital organs (pancreas, liver)
• In the 3 rd week after conception
– A portion of the ectoderm folds into a neural tube (brain and spinal cord)
• By the end of the 4 th week
– The heart has formed and has begun to beat.
– Eyes, ears, nose, and mouth are also beginning to form.
– Buds which will eventually become arms and legs begin to form
• 30 days after conception the embryo is only about ¼ of an inch. But
10,000 times larger than that of the zygote
During the 2 nd month
– The embryo starts to appear human. Circulatory system is independent. Liver and spleen producing blood from the yolk sac.
– A primitive tail appears which eventually becomes enclosed by protective tissue. Forming back bone or coccyx
Between the 5 th and 7 th week
– Eyes have corneas and lenses, ears are well formed, skeletal system developed. Limbs and muscular system developing.
– Development is occurring in a proximodistal and cephaloclaudal manner
During 7 th and 8 th week
– Sexual development begins to appear (indifferent gonads/genital ridges).
• Male, gene on Y chromosome triggers chemical reaction to produce male testicles.
• If female, gonads will receive no instruction and will produce ovaries
THE PERIOD OF THE FETUS
• All of the structures which will be present when the baby is born are formed at the end of 2 months.
– Body systems become interconnected. Nervous and Muscular system allow for kicking, twisting of body
– Digestive and Excretory allow for swallowing, digest nutrients, urination
– Sexual differentiation increasing rapidly.
• Male testes secrete testosterone—hormone responsible for the development of penis and scrotum. In the absence of testosterone, female genitals are developed.
• By end of 3 rd month, sex can be determined by ultrasound. The reproductive systems already contain immature ova and sperm cells.
All of these developments in a mere 3 months (1 st trimester) and when the fetus is only 3 inches long and weighs less than an ounce
• Motor activities become refined actions such as thumb sucking or kicking strong enough to be felt by the mother
• Heartbeat can be detected using a stethoscope and the hardening skeleton can be detected with ultrasound
• Nails harden, skin thickens, eyebrows, eyelashes, and scalp hair appears
• The fetus is now covered by a white cheesy substance called
(protects skin from chapping) and a fine layer of body hair called
helps vernix stick to the skin
• By the end of 2 nd functional trimester, fetus visual and auditory senses become
• All organs mature rapidly/ preparing the fetus for birth
• 7 months from conception
– Fetuses reach the age of viability (a point by which survival outside of the mother’s uterus may be possible)
Signs of viability
• Organized and consistent heart rate activity
• Gross motor activity
• Sleepiness/waking activity (Determined thru fetal monitoring techniques).
– However, children born prematurely still require oxygen assistance because of immature air sacs in the lungs called pulmonary alveoli
• By the end of 7 months
– Fetus weighs nearly 4 pounds and 16 inches long.
– A month later, the fetus has grown an extra pound or two and grown a inch or two longer due to fat accumulation
(regulation of body temp).
– By the middle of the 9 th month, fetal activity slows and sleep increases
• Fetus is now so large that the most comfortable position is head down at the base of the uterus/ limbs curled in a fetal position
ENVIRONMENTAL INFLUENCES ON
– External agents such as viruses, drugs, chemicals, and radiation that can harm a developing embryo or fetus by causing physical deformities, severely restricting growth, blindness, brain damage, and even death
• About 95% of newborn babies are perfectly normal and that many of those born with defects have mild, temporary, or reversible problems
• The effects of teratogens are worst on a body part during the period when that structure is forming or growing most rapidly
Not all embryos or fetuses are equally affected by a teratogen (genes and prenatal care play a vital role)
– Similar defects can be caused by different teratogens
A variety of defects can result from a single teratogen
• The longer the exposure to or higher the dose of a teratogen, the greater the severity of harm
Embryos/fetuses can be affected by fathers and mothers exposure to teratogens
• The long-term effects of a teratogen often depend on the quality of the postnatal environment
• A period during which an organism is highly susceptible to certain environmental influences.
– Teratogens may still have impact but greater exposure may be required.
• Most organs and body parts are forming during the period of the embryo (3 to 8 wks).
– Therefore, exposure during this period may have serious consequences.
– This is also the time when a woman may not even know that she is pregnant that the embryo is most vulnerable to teratogens.
• Some diseases are small enough to cross the placental barrier and affect developing embryo (immature immune system)
– Rubella (German measles)—mothers who contract this early in pregnancy delivered babies who were blind, deafness, cardiac abnormalities, and mental retardation (most serious during 1 st tri but impactful during 2nd.
– Toxoplasmosis—caused by a parasite found in animals. Generally causes severe eye and brain damage. Even abortion.
– Sexually Transmitted Diseases—most common teratogens and generally more hazardous.
• Syphillis—can cause eye, ear, bone, heart, brain damage
• Genital Herpes—kill about 1/3 affected newborns, cause blindness, brain damage, neurological disorders
• AIDS—worldwide, nearly 4 million women of childbearing age carry this virus and can transmit it to their young. ZDV an antiviral drug used to treat aids improve longevity of life however, those affected by aids will eventually die due to complication
• The Thalidomide Tragedy
– Drug used in the 1960s to reduce the occurrence of morning sickness.
– Pretests with rats revealed no harmful effects
– Thousands of women who used this drug in the 1 st trimester produced severe deformities: eyes, ears, noses, and hearts.
• Many developed Phocomelia
– A structural abnormality in which all or parts of limbs were missing and the feet and hands may be attached directly to the torso (similar to flippers)
• Causes microcephaly (small head)
• Malformations to heart, limbs, joints, and face
• FAS babies display excessive irritability, hyperactivity, seizures, and tremors. Generally, smaller and lighter than most babies.
• Physical and cognitive growth lags
– Produces heart defects when taken during 1 st trimester
• Sex hormones found in contraceptives—heart defects and mild deformations
• Diethylstilbestrol (DES)
– Used mid 1940’s to 1965—synthetic hormone formally prescribed to prevent miscarriages, found to produce cervical cancer in female offsprings and genital tract abnormalities in males
• Cigarette smoking found to cause spontaneous abortion.
– Low birth weight
• Increased in respiratory infections
• Poorer cognitive performance
• Should we pass laws surrounding alcohol consumption and pregnancy?
– Found to have few physical defects. Babies display tremors, sleep disturbances, lack of interest in the environment in early life
– Few physical defects, increased risk for miscarriages, premature deliveries, SIDS
• 1 st month is difficult for these babies but start to normalize
– Increased risk for physical defects.
– Problems with blood restriction/pressure.
– Miscarriages/premature births
Mothers generally advised to gain 25/30 pounds. Doctors now focus on a healthy (high protein and calorie) and nutritious diet
– Severe malnutrition stunts growth. Also, additional effects depends on the trimester
Malnourished babies show cognitive defects/behavioral problems later in childhood. Imbalance of brain cells
Continue malnutrition after birth leads to irritability which affect the parent/child attachment and reduce the amount of facilitated play and supportive interaction that could foster healthy social and emotional development
Small amounts of zinc and magnesium have been found to improve placenta & reduce difficult pregnancies
Folic acid found to prevent down syndrome, spinal bifida, anencephaly, and other defects of the neural tube (most women consume less than half the recommended daily amount needed)
Massive campaigns to produce awareness but controversial due to the assumption that more is better
MOTHERS EMOTIONAL WELL-BEING
• Prolonged stress can have a detrimental impact on fetal development.
– Stress produces chemical responses that is released in the blood and pass the placental barrier. Consequently, causing premature delivery, low birth, stunted growth
• Stress may also weaken the mother’s immune system, consequently, increase the risk of impactful diseases
• Stress appears to be most impactful when the mother has poor coping skills. Other concerning factors:
– Ambivalent/negative about their marriage or pregnancy
– No social support systems
• The safest time to bear a child appears to be around age
16 to age 35 (
– Younger teens are at risk because they are likely impoverished, high levels of stress, and have little access to supervised prenatal care
– Teen moms are generally not at risk when they receive adequate prenatal care
– Older moms risk spontaneous abortion, genetic dysfunctions
• Adequate prenatal care is the key among all moms irrespective of age
THE BIRTH PROCESS
• Child birth is a 3 stage process
– 1 st stage—the period of the birth process lasting from the first regular uterine contractions until the cervix is fully dilated
– 2 nd stage—the period during which the fetus moves through the birth canal and emerges from the mother’s body
– 3 rd stage—expulsion of the placenta
The Baby’s Experience
• Babies are born under stress but their own stress hormones enable them to withstand the stressors of the birthing process.
• Generally babies born blush in color due to oxygen deprivation. They also pass thru a narrow cervix and birth canal (resulting flattened noses, misshapen foreheads, and mild bumps and bruises
• Generally about 20 inches long and weights about 7 to
• An assessment for the newborn’s heart rate, respiration, color, muscle tone, and reflexes that is used to gage perinatal stress and to determine whether a neonate requires immediate medical assistance.
– Score range 0-10 with 7 being normal.
Generally done at birth and 5 minutes later to determine improvement.
Neonatal Behavioral Assessment Scale
• A test that assesses a neonate’s neurological integrity and responsiveness to environmental stimuli
• Typically administered few days after birth. Measures the strength of 20 inborn reflexes, changes in infant’s state, and reactions to comforting and other social stimuli
– Low scores due to slow responses may be indication of brain damage
– If reflexes are good but sluggish or irritable when responding to social stimuli—indication that they may need more playful stimulation
• Only 20 years ago, most hospitals barred fathers from delivery rooms and quickly removed babies once they were born
• Today, 99% of children are born in hospitals.
• Some research that the first 6 to 12 hours are a sensitive period for emotional bonding between parents and the newborn
• Postpartum Depression
– Hormone changes in the mother sometimes cause depression. Elevated and extended depression leads to the diagnosis. Occurs in 10% on new moms
• New fathers display engrossment. Intense fascination.
• 3 birthing complications that can affect development:
– Anoxia (oxy deprivation)
– Low birth weight
– Premature delivery
• ANOXIA (occurs in 1% of cases)
– Breech babies at risk due to tangling of umbilical cord
– Detachment of umbilical cord
– Birth sedatives cross placenta
– Genetic incompatibility between Rh positive fetus and Rh negative mother
– Delayed motor and mental development (3 to 7yrs)
Low Birth Weight
• Due to such factors as drug usage and malnourishment. Tends to be higher among low-income women from ethnic minority groups due to elevated levels of stress and poor education about prenatal care
• Increased risk of SIDS, generally due to respiratory distress syndrome (irregular breathing patterns)
• Preterm babies
– Babies born more than 3 weeks before due date
• Small-for-date babies
– Infants whose birth weight is far below normal, even when born close to their normal due dates