2. Prenatal Growth Three main periods of prenatal development
Germinal Period (1st two weeks after conception): Rapid cell division and beginning of cell differentiation
Embryonic Period (3rd through 8th week): Basic forms of all body structures develop
Fetal Period (9th week until birth): Fetus grows in size and matures in functioning

3. Prenatal Growth Can you define these terms? Beginning of pregnancy
Length of pregnancy
Trimesters
Due date
See Table 4.1 for additional information.
Popular and professional books use various phrases to segment the stages of pregnancy. The following comments may help to clarify the phrases used.
Beginning of pregnancy: Pregnancy begins at conception, which is also the starting point of gestational age. However, the organism does not become an embryo until about two weeks later, and pregnancy does not affect the woman (and is not confirmed by blood or urine testing) until implantation. Perhaps because the exact date of conception is usually unknown, some obstetricians and publications count from the woman’s last menstrual period (LMP), usually about 14 days before conception.
Length of pregnancy: Full-term pregnancies last 266 days, or 38 weeks, or 9 months. If the LMP is used as the starting time, pregnancy lasts 40 weeks, sometimes expressed as 10 lunar months. (A lunar month is 28 days long.)
Trimesters: Instead of germinal period, embryonic period, and fetal period, as used in this text, some writers divide pregnancy into three-month periods called trimesters. Months 1, 2, and 3 are called the first trimester; months 4, 5, and 6, the second trimester; and months 7, 8, and 9, the third trimester.
Due date: Although a specific due date based on the LMP is calculated, only 5 percent of babies are born on that exact day. Babies born between three weeks before and two weeks after that date are considered full term, although labor is often induced if the baby has not arrived within 7 days of the due date. Babies born more than three weeks early are preterm, a more accurate term than premature.

4. First Stages of the Germinal Period
The original zygote as it divides into (a) two cells, (b) four cells, and (c) eight cells Occasionally at this early stage, the cells separate completely, forming the beginning of monozygotic twins, quadruplets, or octuplets.

5. Germinal Period: First 14 Days
Zygote begins duplication and division within hours of conception.
Development of the placenta
Implantation (about 10 days after conception)
Organism grows rapidly
The Most Dangerous Journey
In the first 10 days after conception, the organism does not increase in size because it is not yet nourished by the mother.
Number of cells increases rapidly as the organism prepares for implantation, which occurs successfully about one-half of the time.
Development of the placenta
Organ that surrounds the developing embryo and is attached to the wall of the uterus
Sustains life via the umbilical chord (nourishes organism and carries waste products away)
Implantation (about 10 days after conception)
Developing organism burrows into the placenta that lines the uterus
Organism grows rapidly
Pregnancy can be detected due to new chemicals in the mother's urine

6. Vulnerability During Prenatal Development
The Germinal Period
About half of all conceptions fail to grow or implant properly and thus do not survive the germinal period. Most of these organisms are grossly abnormal.
The Embryonic Period
About 20 percent of all embryos are aborted spontaneously, most often because of chromosomal abnormalities.
The Fetal Period
About 5 percent of all fetuses are aborted spontaneously before viability at 22 weeks or are stillborn (defined as born dead after 22 weeks).
Birth
About 31 percent of all zygotes grow and survive to become living newborn babies.

7. The Embryonic Period: From the Third Through Eighth Week
Primitive streak becomes the neural tube and later forms the brain and spine of the CNS.
Head takes shape.
Eyes, ears, nose, and mouth form.
Heart begins to pulsate.
Extremities develop and webbed fingers and toes separate.
Developing human organism from about the 3rd through the 8th week after conception
Begins when the primitive streak appears down the middle of the cell mass

8. The Embryonic Period (a) 4 weeks past conception (b) 7 weeks
OMIKRON/SCIENCE SOURCE
PETIT FORMAT/SCIENCE SOURCE
(a) At 4 weeks past conception, the embryo is only about 1⁄8 inch (3 millimeters) long, but already the head has taken shape
(b) By 7 weeks, the organism is somewhat less than an inch (2 centimeters) long. Eyes, nose, the digestive system, and even the first stage of toe formation can be seen.
(a) 4 weeks past conception (b) 7 weeks

9. The Fetal Period Fetus 9th week after conception until birth
Genitals form and sex hormones cause differences in brain organization
Cephalocaudal and proximodistal growth
Heartbeat detectable via stethoscope
Cortex is not fully mature at birth
Brain at birth is biggest part of baby
Term: ultrasound

10. Fetus: From Ninth Week Until Birth
The third month
Rapid growth with considerable variation
Average: 3 months; 3 ounces; 3 inches
9th week: SRY gene triggers development of sex organs
3rd month: Neurological sex differences begin
By the end of the third month, the sex organs are visible via ultrasound (also called sonogram), which is similar to an X-ray but uses sound waves instead of radiation.
There’s Your Baby For many parents, their first glimpse of their future child is an ultrasound image. This is Alice Morgan, 63 days before birth.

11. Fetus: The Middle Three Months
Digestive and excretory system develop
Fingernails, toenails, and buds for teeth form, and hair grows (including eyelashes)
Viability This fetus is in mid-pregnancy, a few weeks shy of viability. As you can see, the body is completely formed. Unseen is the extent of brain and lung development; it will take at least another month for these organs to become sufficiently mature to allow for survival.
For many more weeks, the fetus must depend on the translucent membranes of the placenta and umbilical cord (the long white object in the foreground) for survival.

12. Fetus: The Middle Three Months
Brain
Experiences rapid growth
Follows proximodistal sequence from brainstem to midbrain, to cortex
Develops many new neurons (neurogenesis) and synapses (synaptogenesis)
Begins to regulate basic bodily functions as entire CNS becomes responsive
Up to half a million brain cells per minute are created at peak growth during mid-pregnancy.

13. Prenatal Growth of the Brain
Prenatal Growth of the Brain Just 25 days after conception (a), the central nervous system is already evident. The brain looks distinctly human by day 100 (c). By the 28th week of gestation (e), at the very time brain activity begins, the various sections of the brain are recognizable. When the fetus is full term (f), all the parts of the brain, including the cortex (the outer layers), are formed, folding over one another and becoming more convoluted, or wrinkled, as the number of brain cells increases.

14. Fetus: The Final Three Months
Last three months
Involves expansion and contraction of lungs
Includes final maturation of heart valves, arteries, and veins
Provides time for extensive growth and folding in cortex
LOYOLA UNIVERSITY HEALTH SYSTEM, HO/AP PHOTO
Rumaisa gained 5 pounds (2,270 grams) in the hospital and then, six months after her birth, went home. Her twin sister, Hiba, who weighed 1.3 pounds (590 grams) at birth, had gone home two months earlier.
At their one year birthday, the twins seemed normal, with Rumaisa weighing 15 pounds (6,800 grams) and Hiba, 17 pounds (7,711 grams).
One of the Tiniest Rumaisa Rahman was born after 26 weeks and 6 days weighing only 8.6 ounces (244 grams). She has a good chance of living a full, normal life.

15. Birth
Fetal brain signals the release of hormones to trigger the female's uterine muscles.
Labor begins
Average duration for firstborn babies: 12 hours
Quicker labor for later-born babies
Birthing positions vary
Sitting, squatting, lying down, water births
Cultural and personal preference

16. Choice, Culture, or Cohort?
Why do it that way? Both of these women (in Peru, on the left, in England, on the right) chose methods of labor that are unusual in the United States, where birth stools and birthing pools are uncommon. However, in all three nations, most births occur in hospitals—a rare choice a century ago.

17. A Normal, Uncomplicated Birth
(a) The baby's position as the birth process begins.
(b) The first stage of labor: The cervix dilates to allow passage of the baby's head.
(c) Transition: The baby's head moves into the “birth canal,” the vagina.
(d) The second stage of labor: The baby's head moves through the opening of the vagina (“crowns”) and (e) emerges completely,
followed by the rest of the body about a minute later. (f) The third stage
of labor is the expulsion of the placenta. This usually occurs naturally,
but it is crucial that the whole placenta be expelled,
so birth attendants check carefully. In some cultures, the placenta is ceremonially buried, to commemorate
the life-giving role it plays.

18. The Newborn’s First Minutes
Usually cry spontaneously
Color changes from bluish to pinkish
Eyes open, fingers grab, toes stretch
Apgar scale
Quick assessment of newborn's heart rate, breathing, muscle tone, color, and reflexes
Completed twice (1 minute and 5 minutes after birth)
Score of 0, 1, or 2 in each category
Desired score: 7 or above

19. Criteria and Scoring of the Apgar Scale
Apgar scale. A quick assessment of a newborn’s health. The baby’s color, heart rate, reflexes, muscle tone, and respiratory effort are given a score of 0, 1, or 2 twice- at one minute and five minutes after birth-and each time the total of all five scores is compared with the maximum score of 10 (rarely attained).

20. Medical Assistance
Characteristics of childbirth depend on several variables.
Parents’ preparation
Position and size of fetus
Customs of culture
In most developed nations childbirth includes
Sterile procedures
Electronic monitoring
Drugs to dull pain or speed contractions
Cesarean Section (c-section)
Surgical birth
Fetus can be removed quickly
Rates and reasons for c-sections vary
Lower rates in poorer countries
Higher rates in richer countries
1/3 of births in the United States
Less trauma for the newborn but slower recovery for the mother
Subsequent cesarean deliveries may be necessary

21. Medical Assistance Surgery: Epidural
Injection in particular part of spine to alleviate pain
Often used in hospital births
Increase rate of cesarean sections and decrease the readiness of newborn infants to nurse
Surgery: Induced labor
Drug used to start, speed, or strength labor
Increase rate; now used in about 20% of U.S. births

22. Medical Assistance Surgery: Cesareans Are controversial
Involve surgical birth
Vary by rates and reasons for use
Present advantages for hospitals; more complications after birth
Pick Up Your Baby!
Probably she can’t. In this maternity ward in Beijing, China, most patients are recovering from Cesarean sections, making it difficult to cradle, breast-feed, or carry a newborn until the incision heals.
Cesarean section (c-section): A surgical birth, in which incisions through the mother’s abdomen and uterus allow the fetus to be removed quickly, instead of being delivered through the vagina. (Also called simply section.)

23. Rate of Cesarean Section
Too Many Cesareans or Too Few? Rates of cesarean deliveries vary widely from nation to nation. Latin America has the highest rates in the world (note that 40 percent of all births in Chile are by cesarean), and sub-Saharan Africa has the lowest (the rate in Chad is less than half of 1 percent). The underlying issue is whether some women who should have cesareans do not get them, while other women have unnecessary cesareans.

24. Alternatives to Hospital Technology
Home births
Doula
Woman who helps with labor, delivery, breast-feeding, and newborn care
May be related to lower rate of cesarean sections
Pressure Point Many U.S. couples, like this one, benefit from a doula’s gentle touch, strong pressure, and sensitive understanding—all of which make doula births less likely to include medical intervention.

25. Problems and Solutions
Harmful substances
Prenatal teratogens
Any agent or condition, including viruses and drugs, resulting in birth defects or complications
Behavioral teratogens
Agents and conditions that can harm the prenatal brain, impairing the future child's intellectual and emotional functioning
Not all teratogens can be avoided
Structural abnormalities are obvious at birth

26. Risk Analysis Factors
Risk analysis discerns which chances are worth taking and how risks are minimized.
Critical time
Dose and/or frequency of exposure (threshold effect)
Innate vulnerability
Risk analysis
Discerns which chances are worth taking and how risks are minimized
Teratology
Science of risk analysis

27. Critical Periods in Human Development
The most serious damage from teratogens (green bars) is likely to occur early in prenatal development. However, significant damage (purple bars) to many vital parts of the body, including the brain, eyes, and genitals, can occur during the last months of pregnancy as well.

28. Risk Analysis: How Much Is Too Much?
Threshold effect
Certain teratogens are relatively harmless until exposure reaches a certain level.
Thresholds are controversial
Example: Alcohol consumption
Embryo exposed to heavy drinking can develop fetal alcohol syndrome (FAS).
FAS is more apparent when women are poorly nourished and cigarette smokers.

29. Risk Analysis: Innate Vulnerability
Genetic vulnerability
Some zygotes carry genes that make them vulnerable.
Male fetuses are more vulnerable to teratogens than female ones.
Mother’s genes affect the prenatal environment she provides.
Neural-tube defects are more common in certain ethnic groups (e.g., Irish, English, and Egyptian).
Scientists disagree about the strength of the correlation between FAS and drinking alcohol during pregnancy.
Genetic vulnerability is a particular example of differential sensitivity.
Genetic protections or hazards are suspected for many birth defects.

30. Before Pregnancy

31. Risk Analysis: Applying the Research
Advice from Doctors
Advice from Scientists
Problems
Provision of potentially dangerous prescriptions for pregnant women
Failure to take time to understand woman’s life patterns
Problems
Provision of contradictory interpretation of research that led to opposite message
See Table 4.5 for lists of some teratogens and their possible side effects

32. Prenatal Diagnosis
Early care protects fetal growth, makes birth easier, and renders parents better able to cope.
When complications arise, early recognition increases the chance of a healthy birth.
About 20% of early pregnancy tests raise anxiety instead of reducing it.
False positives
In general, early care protects fetal growth, makes birth easier, and renders parents better able to cope.
When complications (such as twins, gestational diabetes, and infections) arise, early recognition increases the chance of a healthy birth.

33. Low Birthweight Birthweight
Low birthweight (LBW)
Very low birthweight (VLBW)
Extremely low birthweight (ELBW)
Preterm
Small for gestational age (SGA)
Birthweight
Low birthweight (LBW)
Less than 2,500 grams (5½ pounds) at birth
Very low birthweight (VLBW)
Under 1,500 grams (3 pounds, 5 ounces) at birth
Extremely low birthweight (ELBW)
Under 1,000 grams (2 pounds, 3 ounces) at birth
Preterm
Birth that occurs at 35 or fewer weeks after conception
Usually associated with low birthweight
Small for gestational age (SGA)
Birthweight is significantly lower than expected, given the time since conception.
Many of the risk factors just mentioned—underweight, undereating, underage, and smoking—tend to occur together.

34. Low Birthweight and the Mother
Maternal behavior
Maternal health and illness
Maternal drug use before and during pregnancy
Maternal malnutrition
Fathers and others
Father attitudes and behaviors
Hispanic paradox
Hispanic paradox
The surprising discovery that, although low SES usually correlates with poor health, this is not true for Hispanics in the United States.
For example, when compared with the U.S. average LBW rate, Hispanic newborns are less often of low birthweight.

35. What about the Father?
Indirect influence of risk for adverse birth outcomes (Misra et al., 2010)
Father’s attitude
Father’s behavior
Relationship between mother and father
Hispanic paradox

36. Low Birthweights: Comparing Nations
United States has a low-birthweight rate of about 8.2 percent-ranking worse than most developed nations.
Worldwide, far fewer low-birthweight babies are born today than 20 years ago.
Neonatal deaths have been reduced by one-third as a result.
Getting Better. Some public health experts consider the rate of low birthweight to be indicative of national health, since both are affected by the same causes. If that is true, the world is getting healthier, since the LBW world average was 28 percent in 2009 but 16 percent in When all nations are included, 47 report LBW at 6 per 100 or lower (United States and United Kingdom are not among them).

37. Consequences of Low Birthweight
High risk infants and children
Are later to smile, to hold a bottle, to walk, and to communicate
In middle childhood, formerly SGA children
Have smaller brain volume
Remember that risk analysis gives odds, not certainties!

38. Complications During Birth
When a fetus is at risk, birth complications become likely
Example: Cerebral palsy
Anoxia-related damage related to varied factors, such as
Genes
Birthweight
Gestational age
Drugs in bloodstream
When a fetus is at risk because of low birthweight, preterm birth, genetic abnormality, or teratogen exposure, or when a mother is unusually young, old, small, or ill, birth complications become likely.

39. The New Family: The Newborn
Newborns seek to protect themselves with three sets of reflexes
Maintaining oxygen: Breathing, hiccupping, sneezing
Maintaining constant body temperature: Crying, shivering, tucking legs to body, pushing
Managing feeding: Sucking, rooting, swallowing
Reflex: An unlearned, involuntary action or movement in response to a stimulus.
A reflex occurs without conscious thought.

40. The Newborn Brazelton Neonatal Behavioral Assessment Scale (NBAS)
Test often administered to newborns that measures responsiveness and records 46 behaviors, including 20 reflexes
Parents who watch their infant perform on the NBAS are amazed at the newborn’s responses—and this fosters early parent–child connection.

41. The New Family: The Newborn
Other reflexes are not necessary for survival but signify the state of brain and body functions
Babinski reflex
Stepping reflex
Palmar grasping reflex
Moro reflex
Babinski reflex. When a newborn’s feet are stroked, the toes fan upward.
Stepping reflex. When newborns are held upright, feet touching a flat surface, they move their legs as if to walk.
Swimming reflex. When held horizontally on their stomachs, newborns stretch out their arms and legs.
Palmar grasping reflex. When something touches newborns’ palms, they grip it tightly.
Moro reflex. When someone bangs on the table they are lying on, newborns fling their arms outward and then bring them together on their chests, crying with wide-open eyes.

42. The New Family: Fathers
Not only fathers, but the entire social network and culture are crucial influences
Father's role
Helping mother stay healthy
Helping mother manage stress (affects fetus)
Providing legal acceptance the birth
Couvade
Symptoms of pregnancy and birth experienced by fathers
Newborns born in the United States to immigrants are generally healthier in every way, including in birthweight, than are newborns of American-born women of the same ethnicity

43. The New Family: Mothers
About half of all women experience physical problems after birth.
Between 8 and 15% of women experience postpartum depression.
Feelings of sadness and inadequacy
Symptoms from baby blues to postpartum psychosis
May involve struggles with adequate baby care
Varied causes
About half of all women experience physical problems after giving birth
Sadness and inadequacy felt by 8-15% of new mothers in the days and weeks after giving birth
Symptoms range from baby blues to postpartum psychosis
Depressed mothers find baby care burdensome and may think about mistreating the infant
Paternal involvement can have beneficial effect
Causes for postpartum depression vary
Problems include such things as incisions from a c-section, painfully sore nipples, or problems with urination.

44. Parental Alliance Parental alliance
Involves commitment by both parents to cooperate in raising the child
Is especially beneficial when infant is physically vulnerable

45. Bonding Parent-infant bond
Bonding involves strong, loving connection that forms as parents hold, examine, and feed the newborn.
Early skin-to-skin contact is not essential for human bonding.

46. Bonding
Kangaroo care benefits mothers, babies, and hospitals, saving space and medical costs in this ward in Manila.
Kangaroo care is one reason Filipino infant mortality in 2010 is only one fifth of what it was in 1950.
Kangaroo care
Child-care technique in which the mother of a low-birthweight infant holds the baby between her breasts
Allows baby to hear mother's heartbeat and feel her body heat
Research confirms beneficial effects