Unit 2

Question 1

What are three things that are needed for fertilization to occur?

Answer 1

1. Equal maturation of both sperm and ovum
2. Ability of the sperm to reach the ovum
3. The ability of the sperm to penetrate the ovum and reach fertilization

Question 2

What are the three stages of fetal development?

Answer 2

1. Preembryonic
2. Embryonic
3. Fetal

Question 3

What occurs during the first stage of fetal development?

Answer 3

This is the pre-embyronic stage. This lasts from conception until day 14. This covers cellular replication, blastocyst formation, initial development and establishment of primary germ layers.

Question 4

What occurs during the second stage of fetal development.

Answer 4

This is the embryonic stage. This lasts form day 15-8 weeks after conception. This is the most critical time for the development of the organ systems and the main external features. This time is very vulnerable to teratogens.

Question 5

What occurs during the third stage of fetal development?

Answer 5

This is the fetal stage. This stage lasts from 9 weeks until the end of pregnancy. Changes in this period are not as dramatic because refinement is taking place. The fetus is less vulnerable to teratogens, except those that affect the CNS.

Question 6

What are chorionic villi?

Answer 6

They are formed from the blastocyst after implantation is complete. They reach into the uterine endometrium and begin forming the placenta.

Question 7

What is a placenta?

Answer 7

The placenta grows out of the trophoblast tissue. It allows oxygen and other nutrients to move from maternal blood through chorionic villi to embryo. This serves as the fetal lungs, kidneys, and digestive tract while in utero.

Question 8

What is decidua?

Answer 8

The thickening of the endometrial wall. This is sloughed off after birth.

Question 9

What is the purpose of amniotic fluid?

Answer 9

Amniotic fluid is clear and colorless. It maintains an even temperature. It prevents sacs from adhering to embryo, allows for movement and symmetrical development and acts as a cushion to protect the fetus.

Question 10

What volume of amniotic fluid should be present at 10 weeks? at 20 weeks? at term delivery?

Answer 10

10 weeks: 30mls
20 weeks: 350 mls
Term: 1200mls

Question 11

What is Oligohydramnios? What are some causes of it?

Answer 11

A condition in which there is too little amniotic fluid. This can be caused by rupture of the membranes, poor fetal growth and carrying past the due date.

Question 12

What is polyhydramnios? What are some causes of it?

Answer 12

A condition in which there is too much amniotic fluid. This can be caused by gestational diabetes, and fetal abnormalities.

Question 13

What does the Ectoderm layer form?

Answer 13

It forms the CNS, special senses, skin and glands.

Question 14

What does the mesoderm layer form?

Answer 14

It forms the skeletal, urinary, circulatory and reproductive organs.

Question 15

What does the Endoderm layer form?

Answer 15

This forms the respiratory system, liver, pancreas, and digestive system.

Question 16

What hormones are produced by the placenta?

Answer 16

Progesterone: Helps the uterus to grow and prevents contractions.
Estrogen: Helps the uterus to grow and maintains uterine lining.
hCG(Human chorionic gonadotropin): Helps to keep the pregnancy going and maternal recognition of pregnancy.
hPL(Human-placental lacotgen): Helps to regulate metabolism and increases insulin resistance.

Question 17

How many arteries and how many veins are on the umbilical cord? What kind of blood does each carry? What is Wharton’s jelly?

Answer 17

There are two arteries and one vein.
The arteries carry deoxygenated blood to the fetus.
The vein carries oxygenated blood to the fetus.
Wharton’s jelly makes up the bulk of the cord and provides protection.

Question 18

What is the purpose of the umbilical cord?

Answer 18

The umbilical cord provides circulation between the embryo - chorionic villi of placenta- mom.
It transports oxygen and nutrients to the fetus and waste away from the fetus (to placenta).

Question 19

Does fetal and maternal blood mix?

Answer 19

No, the blood does not generally mix.
Maternal blood spurts into intervillous spaces in the decidua. A thin placental membrane separates maternal from fetal blood, but the membrane is not always an effective barrier.

Question 20

Is fetal circulation the same as extrauterine circulation?

Answer 20

No. There are 3 shunts in place to aid intrauterine circulation that then closes after birth.

Question 21

What are the 3 shunts present in the fetal circulatory system?

Answer 21

1. Ductus venosus
2. Foramen ovale
3. Ductus arteriosus

Question 22

What is the process of fetal circulation?

Answer 22

1. Umbillical vein carries oxygenated blood to the fetus from placenta.
2. Ductus Venosus allows blood to go from the umbillical vein to the inferior vena cava which enters the R atrium along with blood from the superior vena cava.
3. The foramen ovale diverts blood from the right atrium to the left atrium bypassing the lungs (a small amount of blood enters the ventricle and lungs for nutrition)
4. The ductus arteriosus diverts blood from the pulmonary artery into the descending aorta.
5. Umbilical artery brings blood back to the placenta (low resistance) to remove waste and gain nutrients and oxygen.

Question 23

What are some milestones of fetal growth at four weeks?

Answer 23

The heart develops and the double chambers are visible and begins to beat. Primary lung buds appear. Rudimentary ureteral buds appear, A genital ridge appears (5th week). 0.4cm - 0.5cm crown to rump. The fetus weighs 0.4 grams.

Question 24

What are some milestones of fetal growth at 8 weeks?

Answer 24

The body is fairly well formed with a flat nose, far apart eyes and well formed digits, eyes, ears, nose, and mouth are now recognizable. It is 2.5 cm - 3 cm in length. It weights 2 grams. The testes and ovaries are distinguishable, but external structures remain sexless. Intestinal villi are developing, small intestines coil within the umbilical cord. Organs are formed.

Question 25

What are some milestones of fetal growth at 12 weeks?

Answer 25

Nails are appearing, the head is erect but disproportionally large. Skin is pink and delicate. Intestine have withdrawn from the umbilical cord and assume characteristic position. Blood is forming in marrow, the kidneys are able to secrete urine and brain structural configuration is almost complete. The earliest taste buds are formed.

Question 26

What are some milestones of fetal growth at 16 weeks?

Answer 26

Urine is present in the amniotic fluid, Arm and leg ratio is now proportional. Meconium is present in the bowel and the anus is open. The heart muscle is well developed and it is 11.5 cm - 13.5 cm in length. It weights 100 grams and sex can now be identified by ultrasound.

Question 27

What are some milestones of fetal growth at 18 weeks?

Answer 27

Rapid brain growth is occurring. Fetal heart tones can be heard with stethoscope. Vernix caseosa covers the fetus. Eyebrows and head hair appears, Muscles are well developed.

Question 28

What are some milestones of fetal growth at 20 weeks?

Answer 28

Vernix caseosa and lanugo appear. The legs lengthen considerably. The ascending colon is now recognizable. The sternum ossifies. Primitive respiratory like movements begin. The brain is grossly formed and cord myelination occurs. Brown fat begins to form and will aid in temperature regulation at birth.

Question 29

What are some milestones of fetal development at 24 weeks?

Answer 29

Active production of surfactant has begun. The fetus "practices" breathing by inhaling amniotic fluid into its lungs. The body is lean but fairly well proportioned. Blood formation increases in bone marrow and decreases in liver. The baby can hear sounds, is 23 cm in length and weights 600 grams.

Question 30

What are some milestones of fetal development present at 32 weeks?

Answer 30

Subcutaneous fat is beginning to collect, giving it a more rounded appearance. The baby begins to move into the birth position. The sense of taste is present and it is aware of sounds. Testes are descending into the scrotum. The fetus weights 1800-2100 grams and is approximately 31 cm in length.

Question 31

What are the differences between monozygotic twins vs dizygotic twins?

Answer 31

Monozygotic twins are identical twins from one fertilized ovum which divides. They may share a placenta, chorion and amnion. There are risks of prematurity due to over distended uterus and a growth restriction due to placental insufficiency. Dizygotic twins are fraternal. Formed from two separate ova and 2 separate sperm. There are 2 chorions, 2 amnions, and 2 placentas (which can sometimes fuse). The risks are the same.

Question 32

What should be assessed during a fetal wellbeing-assessment?

Answer 32

A complete health history including: Nutritional intake, smoking, ETOH, exercise and any past medical history. Physical examination includes measuring the symphysis fundal height (McDonald method), checking fetal movement and kick counting.

Question 33

What are some fetal wellbeing prenatal tests? What do the results tell us?

Answer 33

Alpha-fetoprotein: A blood test measuring plasma protein from fetus. Typically performed between 15-18 weeks gestation. Increased levels may indicate neural tube defect, turner syndrome or multiple gestation. Decreased levels may indicate down syndrome or trisomy 18. Chorionic villus sampling: The removal of small tissue specimen from the fetal portion of the placenta. Safety concerns include severe transverse limb defects and spontaneous pregnancy loss. This is usually done at 10-12 weeks. With results usually taking less than a week. This is used to detect numerous genetic disorders. Percutaneous umbilical blood sampling: Insertion of a needle directly into a fetal umbilical vessel under ultrasound guidance. Safety concerns include fetal hemorrhage and risk of infection. This is usually done after 16 weeks. Used for prenatal diagnosis of inherited blood disorders and assessment and treatment of isoimmunization. Fetal nuchal translucency: An intravaginal ultrasound that measures fluid collection. This is done between 10-14 weeks. It is used to identify fetal abnormalities. Level 2 ultrasound: The use of high-frequency sound waves to visualize the fetus. It is performed after 18 weeks. It enables evaluation of structural changes to be identified early. Triple and quad screening tests: Include many tests, done between 15-18 weeks and used to identify chromosomal abnormalities. Preimplantation genetic diagnosis: Genetic testing of embryos produced through IVF. Usually done on day 3 after egg retrieval and 2 days after fertilization. This identifies embryos carrying specific genetic alterations that can cause disease. Cell-free fetal DNA: A noninvasive prenatal test using maternal plasma. Taken at approximately 10 weeks. Determines fetal sex in pregnancies at risk for sex-linked conditions.

Question 34

What is an amniocentesis? What are some risks involved? When is it performed?

Answer 34

Amniotic fluid is aspirated from the amniotic sac. Safety concerns include infection, pregnancy loss and fetal needle injuries. This is usually done at 15-28 weeks with results taking 2-4 weeks. It is used to identify inborn errors of metabolism. What to report after: Fever, Leaking amniotic fluid, vaginal bleeding, uterine contractions and changes in fetal activity.

Question 35

What is a teratogen?

Answer 35

Anything that can adversely affect the fertilized ovum, embryo or fetus. It can be microorganisms, environmental, dietary, medications or live virus vaccines. Most susceptible during the first trimester.

Question 36

What is toxoplasmosis?

Answer 36

A widespread parasitic infection. It is transferred by hand to mouth after touching cat feces which changing the cat litter. Can cause a low birth weight, enlarged liver and spleen, jaundice and hydrocephalus in the fetus. The earlier the infection, the more severe the effects. Prevention is key.

Question 37

What is administered after birth to a babe whose mother is gonorrhea positive.

Answer 37

Erythromycin eye ointment is administered during the first hour of like for prophylaxis to prevent ophthalmia neonatorum.

Question 38

What is Cytomegalovirus?

Answer 38

It is the most common congenital and perinatal viral infection in the world. It affects greater than 50% of the human population. Leading cause of hearing loss and intellectual damage/delay. Prenatal screening is not routinely performed, no therapy to treat.

Question 39

How do we measure the symphysis fundal height using the McDonald Method.