Prenatal Growth Three main periods of prenatal development Germinal period Embryonic period Fetal period Germinal period The first two weeks of prenatal development after conception, characterized by rapid cell division and the beginning of cell differentiation. Embryonic period The stage of prenatal development from approximately the third through the eighth week after conception, during which the basic forms of all body structures, including internal organs, develop. Fetal period The stage of prenatal development from the ninth week after conception until birth, during which the fetus gains about 7 pounds (more than 3000 grams) and organs become more mature, gradually able to function on their own.

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.

The Embryonic Period: From the 3rd- 8th Week the neural tube 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.

Fetus The third month Rapid growth with considerable variation Average: 3 months; 100 grams, 100 millimeters 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.

Fetus 4th, 5th and 6th months Digestive system develops Fingernails, toenails, and buds for teeth form, and hair grows (including eyelashes) At the end of 4 months, the fetus, now 6 inches long, looks fully formed but out of proportion—the distance from the top of the skull to the neck is almost as long as that from the neck to the rump.

Fetus Brain Experiences rapid growth 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

Fetus 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 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.

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), 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.

Fetus Age of viability Age at which a preterm newborn may survive outside the mother's uterus if medical care is available About 22 weeks after conception Brain is able to regulate basic body functions (e.g., breathing) Even with advanced medical care, survival of extremely preterm newborns is in doubt. These data come from a thousand births in Sweden, where prenatal care is free and easily obtained. As you can see, the age of viability (22 weeks) means only that an infant might survive, not that it will. By full term (not shown), the survival rate is almost 100 percent. Depends on brain development

Harmful Substances (page 110) Teratogens Any agent or condition, including viruses, drugs, and resulting in birth defects or death Behavioral Teratogens Agents and conditions that can harm the prenatal brain, impairing the future child's intellectual and emotional functioning Critical periods matter! teratogen, defined as anything—drugs, viruses, pollutants, malnutrition, stress, and more—that increases the risk of prenatal abnormalities. Not all teratogens can be avoided Structural abnormalities are obvious at birth

Risk Analysis: How Much Is Too Much? Threshold effect Certain teratogens are relatively harmless until exposure reaches a certain level. Thresholds are controversial 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.

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 (example, anxiety) “prenatal development is not a dangerous period to be feared as much as a natural process to be protected.”

Birth About 266 days later… Oxytocin starts labour and prepares fetus for delivery Birthing process is largely cultural About 38 weeks (266 days) after conception, when the fetus weighs 6 to 8 pounds (3,000 to 4,000 grams), the fetal brain signals the release of hormones, specifically oxytocin, which prepares the fetus for delivery and starts labor. (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 som cultures, the placenta is ceremonially buried, to commemorate the life-giving role it plays.

The Newborn’s First Minutes Usually cry spontaneously Color changes from bluish to pinkish Eyes open, fingers grab, toes stretch

Medical Assistance Surgery: Cesareans Are controversial Involve surgical birth Vary by rates and reasons for use Present advantages for hospitals; more complications after birth From Day One For various reasons, some countries have much higher rates of cesarean deliveries than others.

Medical Assistance Epidural Injection in particular part of spine to alleviate pain. Often used in hospital births (63% of women)

Low Birth weight and the Mother Low Birthweight (LBW): A body weight at birth of less than 5½ pounds (2,500 grams). Become high risk infants and children Maternal behavior Maternal health and illness Malnutrition Maternal drug use before and during pregnancy Fathers and others Father attitudes and behaviors Hispanic paradox

The New Family: Mothers About half of all women experience physical problems after birth. Between 8 and 15% of women experience postpartum depression. https://www.youtube.com/watch?v=yH3WMQO- ooU 5 min Feelings of sadness and inadequacy May involve struggles with adequate baby care Varied causes

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

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.

The Importance of Close Contact Birth complications can have lingering impact on later life. Mothers and fathers should help with early caregiving if newborn must stay in the hospital. Research confirms benefits of skin-to-skin contact