Prenatal Development & Birth
From Zygote to Newborn
1. The Germinal Period: From the moment of conception until 14 days later. The first 7- 10 days constitute
a dangerous journey as the zygote moves down the fallopian tube to implantation in the uterus where it
can be nourished. Rapid cell division & the beginning of cell differentiation follows.
2. The Period of the Embryo: From 14 days until 56 days after conception. During this time all major external
& internal body structures begin to form.
3. The Period of the Fetus: From the ninth week after conception until birth. Age of viability (about 22 weeks).
Note: The brain increases about six times in size & develops many new neurons (neurogenesis) &
synapses (synaptogenesis) in the middle trimester (4 to 6 months).
Ψ Vulnerability During Prenatal Development
The Germinal Period: About 60% of all developing organisms fail.
The Period of the Embryo: About 20% of embryos are aborted spontaneously.
The Period of the Fetus: About 5% of all fetuses are lost.
Birth: About 31% of all zygotes (conceptions) grow & survive.
Risk Reduction
Teratology is the study of birth defects; it is a science of risk management.
Teratogens are the agents & conditions that can impair prenatal development.
Teratogen effect is influenced by
1. the timing of exposure. he time of greatest susceptibility to teratogens is called the critical period. There may also be
an interaction effect whereby the risk of a teratogen causing harm increases when it occurs at the same time as other
teratogen or risk.
2. the amount of exposure. Some teratogens have a threshold effect; that is they are virtually harmless until exposure reaches
a certain level.
3. genetic vulnerability.
Specific Teratogens include:
Major Diseases:
* Rubella
* HIV
Medicinal drugs:
* Tetracycline
* anticoagulants
* bromides
* anticonvulsants
* phenobarbital
* retinoic acid
* most hormones
Nonprescription drugs: such as aspirin, antacids, & diet pills
Ψ The FDA has established guidelines for drug companies to follow in regards to labeling medications
about their affects on reproduction & pregnancy. The FDA Drug Category Ratings can be found on the internet.
Ψ Watch These:
Ψ Thalidomide (tha-lid-o-mide) - first marketed in Europe in the late 1950's. It was used as a sleeping pill & to treat
morning sickness during pregnancy. At that time no one knew thalidomide caused birth defects. In 1998, the FDA gave
approval for it to be marketed in the U.S. specifically for the treatment of a variation of leprosy. Now that the drug is
approved it can be prescribed by doctors for other conditions. Because it may become more available to woman
capable of child bearing, be warned!
Ψ Accutane is a prescription medication used to treat severe modular acne. Accutane can cause severe, life-threatening birth
defects if the mother takes the medication during pregnancy. Even one dose of Accutane can cause major birth defects of the baby's
ears, eyes, face, skull, heart, & brain. Never use Accutane if you are pregnant.
Pregnant women should avoid any medication unless it is recommended by a doctor.
Psychoactive Drugs:
* Alcohol can = FAE & FAS
* Tobacco
* Marijuana
* Heroin
* Methadone
* Cocaine
* Solvents
Things You Should do When Planning a Pregnancy
• Take a multivitamin supplement that has 400 micrograms of folic acid & no more
than 100% of the recommended daily allowance (RDA) of other nutrients.
• Quit smoking.
• Discontinue alcohol use.
• Discontinue all street drug use & obtain addiction counseling if needed.
• Review all medical problems (including STDs) with your doctor.
• Review all prescription medication use with your doctor.
• Stop using any unnecessary over-the-counter medications.
• Gain or loss weight as appropriate, exercise.
• Avoid Toxoplasmosis. This germ is commonly found in raw meat, sheep, lambs &
cat feces. To avoid it:
• Wash your hands after handling raw meat.
• Do not eat raw or undercooked (rare) meat.
• Wash salads & vegetables as any dirt may have been contaminated by cat faeces.
• Wash your hands after handling cats & kittens.
• Get someone else to clean out any cat litter trays when you are pregnant.
• Always wear gloves when gardening.
Low Birth Weight (LBW): Weight at birth of less than 5 1/2 pounds
Risk Factors - LBW, Preterm Birth
- Physical factors
- High dosage of a psychoactive drug
- Extreme stress
- Chronic exhaustion
- Infection
Risk Factors - LBW, Small for Gestation Age (SGA).
- Maternal use of psychoactive drugs ( tobacco/nicotine is the worst )
- Maternal Malnutrition
Ψ IntraUterine Growth Restriction (IUGR)
• Intrauterine growth restriction is a term for a baby who is smaller than
normal during pregnancy. The baby is not growing at the normal rate inside the uterus. These babies usually have
a low weight at birth. Babies who have IUGR are more likely to have health problems (both during pregnancy & after
birth).
• IUGR has various causes. A common cause is a problem in the placenta (the tissue that carries oxygen, food &
blood to the baby). Birth defects & genetic disorders can also cause IUGR. If the mother has an infection, high
blood pressure, kidney disease, heart disease, sickle cell anemia, is smoking, drinking alcohol or abusing drugs,
her baby is at risk. Sometimes prescribed medicines that the mother is taking cause IUGR.
Ψ Virtually all the many risk factors for LBW correlate with poverty.
Kangaroo care is a form of skin-to-skin contact between a parent & their preterm baby. The baby, wearing
only a diaper, is held in an upright position against the parent 's bare chest. The baby is held this way for 20
minutes to four hours a day. This is called Kangaroo Care because it is similar to the way a baby kangaroo
is snuggled against its mother.
Benefits to the baby may include:
* Increased parent-infant bonding
* Comfort from hearing the parent's heart beat
* Earlier breast-feeding
* Decreased time spent in the hospital
* Increased ability to keep warm
* Increased deep sleep states
* Decreased breathing pauses & apnea
* Increased oxygen level
* Decreased number of slow heart rate spells
Benefits to parents may include:
* Increased parent-infant bonding
* Increased breast milk supply
* Earlier breast-feeding
* Continuous breast-feeding for longer periods of time
* Increased readiness for discharge
* Increased confidence in ability to care for baby
* Increased sense of control
* Increased ability to cope with the stress of having a high-risk infant
The Normal Birth - The baby is born, on average, after 12 hours of active labor for first births
& after seven hours for subsequent births although it is not unusual for labor to be from half to twice as long.
Apgar Scoring for Newborns A score is given for each sign at one minute & five minutes
after the birth. If there are problems with the baby an additional score is given at 10 minutes. A
score of 7-10 is considered normal, while 4-7 might require some resuscitative measures, and a baby
with an apgar of 3 and below requires immediate resuscitation.
Sign: Activity (muscle tone)
0 — Limp; no movement
1 — Some flexion of arms and legs
2 — Active motion
Sign: Pulse (heart rate)
0 — No heart rate
1 — Fewer than 100 beats per minute
2 — At least 100 beats per minute
Sign: Grimace (reflex response)
0 — No response to airways being suctioned
1 — Grimace during suctioning
2 — Grimace and pull away, cough, or sneeze during suctioning
Sign: Appearance (color)
0 — The baby's whole body is completely bluish-gray or pale
1 — Good color in body with bluish hands or feet
2 — Good color all over
Sign: Respiration (breathing)
0 — Not breathing
1 — Weak cry; may sound like whimpering, slow or irregular breathing
2 — Good, strong cry; normal rate and effort of breathing
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Growth & Development
Robert C. Gates