Chapter 3 Prenatal development and Birth

Infertility

Infertility

• Not being able to get pregnant after a year of trying

• Stems from a variety of causes

• Equally attributed to men and women

Varicocele

A condition affecting men in which enlarged veins on their testicles increase the temperature in the testes, interfering with sperm production (low)

Endometriosis

A condition affecting women when bits of tissue lining the uterus grow outside of the uterus

Artificial insemination:

• Also called intrauterine insemination (IUI=first option for TX.)

• Involves injecting sperm into the uterus

In vitro fertilization (IVF):

• Several eggs are removed from a woman’s ovary and manually combined with sperm in a laboratory.

• Returned to uterus in hopes that one egg will implant

Germinal period

• First trimester begins with this period.

• Lasts approximately 2 weeks

• Zygote divides many times through mitosis, forming the blastocyst.

• Hollow ball of about 150 cells that is the size of the head of a pin

Day 1

Fertilization usually occurs within 24 hours of  ovulation (process in which a mature egg is released from the ovary).

day 2

The single-celled zygote begins to divide 24–36 hours after fertilization.

day 3

The mass has 12–16 cells; it is traveling down the fallopian tube to the fetus.

day 4-5

An inner cell mass forms; the entire mass is called a blastocyst (made up of an inner group of cells with an outer shell. The inner group of cells will become the embryo) and is the size of a pinhead

day 6-7

The blastocyst attaches to the wall of the uterus.

day 8-14

During the second week, the blastocyst becomes fully embedded in the wall of the uterus. It now has about 250 cells.

Embryonic period

Occurs from the third to the eighth week after conception

Organogenesis

Time period when every major organ takes shape

Placenta

• Tissue fed by blood vessels from the mother and connected to the embryo by the umbilical cord

• Toxins released, oxygen received-lung, kidney, nutrition, immunity.

week 3

Now an embryo, the person-to-be is just 1/10 of an inch (2 mm) long. It has become elongated, and three layers emerge—the ectoderm, mesoderm, and endoderm.

week 4

The embryo is so curved that the two ends almost touch. The outer layer (ectoderm) folds into the neural tube. From the mesoderm, a tiny heart forms and begins to beat. The endoderm differentiates into a gastrointestinal tract and lungs. Between days 21 and 28, eyes develop.

week 5

Ears, mouth, and throat take shape. Arm and leg buds appear. The handplate, from which fingers will emerge, appears. The heart divides into two regions, and the brain differentiates into forebrain, midbrain, and hindbrain.

week 6-7

The embryo is almost 1 inch long. The heart divides into four chambers. Fingers emerge from the handplate, and primitive facial features are evident. The important process of sexual differentiation begins.

week 8

Most structures and organs are present. Ovaries and testes are evident. The embryo begins to straighten and assumes a more human appearance.

week 9

Bone tissue emerges, and the embryo becomes a fetus. The head of the fetus takes up about half of the total length of the fetus. The fetus can open and close its mouth and turn its head.

week 10-12

Fingers and toes are formed. External genitalia have developed. Movements have increased and the fetus shows breathing movements with its chest and some reflexes.

week 13-16

The heartbeat should be audible with a stethoscope. Fetal movements may become apparent to the mother. The fetus is about 4.5 inches long and the skeleton is becoming harder.

week 17-22

Fingernails, toenails, hair, teeth buds, and eyelashes grow. Brain development is phenomenal, and brainwaves are detectable.

week 23-25

This is the age of viability. The fetus is about 12 inches long and weighs about 1 pound.

week 26-32

The fetus gains weight and the brain grows. The nervous system becomes better organized.

week 33-38

There is further weight gain and brain activity. The lungs mature and begin to expand and contract.

teratogen

• Any disease, drug, or other environmental agent that can harm a developing fetus

  • Effects are worse during the critical period (embryonic period)

  • The greater and longer exposure, the more likely serious damage will occur.

  • Susceptibility to harm influenced by genetic makeup

  • Effects depend on the quality of the prenatal and postnatal environments.

Thalidomide

• Used to relieve morning sickness in 1950s

• It later became clear that there are critical periods for different deformities caused by thalidomide.

  • If mother had taken thalidomide 20–22 days, the baby was born without ears.

  • At 22–27 days after conception, the baby often had missing or small thumbs.

  • At 27 and 33 days, baby was likely to have stunted legs.

  • At 35 or 36 days after conception, baby was not affected.

tabaco

• Effects of smoking during pregnancy are varied and may include:

  • Increased risk of miscarriage

  • Prematurity, growth retardation, and small size

  • Respiratory problems

  • Problems with attention and impulsivity

  • Problems with delinquent behavior and substance abuse

  • Raises risk of Sadden Infant Death Syndrome) SIDS

alcohol

• Crosses the placenta

• Disrupts the normal process of neuronal migration

• Can lead to neuronal death

• Fetal alcohol syndrome

  • Noticeable physical symptoms (small head, thin upper lip, short nose, flat midface); signs of CNS damage; lower than average IQ

cocaine

• Can cause spontaneous abortion in first trimester

• Premature detachment of placenta and fetal strokes later in pregnancy

• Contributes to fetal malnourishment, retarded growth, and low birth weight

opioids

• Smaller babies and early delivery

• Increased risk of cesarean section delivery and respiratory support

• Neonatal Abstinence Syndrome (NAS): withdrawal from the drug

aids

• Can be transmitted to babies

• Prenatally: virus passes through the placenta

• Perinatally: blood exchanged between mother and baby (immediately after birth)

• Postnatally: virus transmitted during breastfeeding

syphilis

• Can cause miscarriage or stillbirth in approximately 25% of cases

• Blindness

• Intellectual disability

radiation

• Higher-than-normal rate of intellectual disability,  greater incidence of leukemia and cancers

pollutants

• Lower birth weight

• Preterm birth

• Impaired intellectual functioning

malnutrition

• First trimester disruption of formation of spinal cord, fewer brain cells, and stillbirth

• Third trimester smaller neurons, smaller brain, and smaller child

• Can lead to mental impairment

maternal obesity

Offspring obesity and diabetes

older paternal age

• Odds of miscarriage are higher

• Elevated risk of congenital heart defects, neural tube defects, and kidney problems

• Odds of Down syndrome higher

• Risk factor for schizophrenia

oxygen shortage

• Umbilical cord becomes pinched or tangled.

• Sedatives interfere with baby’s breathing.

• Breech presentation (feet or buttocks first)

severe oxygen shortage

Memory impairment

cerebral palsy

a neurological disability primarily associated with difficulty controlling muscle movements