The Fetal Period: Ninth Week to Birth

Question 1

What are the primary areas of development during the fetal period?

Answer 1

• Rapid body growth
• Differentiation in tissues, organs, and systems

Question 2

What does viability mean? What is the minimum weight at which MOST fetuses survive?

Answer 2

It is the aility of a fetus to survive in the extrauterine environment ( i.e. after birth).

Fetuses weighing less than 500g at birth usually do not survive.

Question 3

What does Intrauterine Growth Restriction refer to? What is the weight range that fetuses survive but are referred to as premature infants?

Answer 3

(IUGR), refers to a full-term fetus with a low birth weight. Fetuses weighing between 1500 and
2500 g survive, but many complications may occur; they are premature infants.

Question 4

In order to estimate the fetal age what measurement is used?

Answer 4

Ultrasound measurements of the crown-rump length (CRL) help determine the size and probable age of the fetus and to provide a prediction of the expected day of delivery.

Question 5

Why might using LMP lead to inaccuracies when calculating the gestational age?

Answer 5

Dating by LMP (menstrual age) may be inaccurate because of variability in length of menstrual cycles (early or late ovulation occurs in 20% of population), faulty memory, recent exposure to oral contraceptives, or bleeding during early pregnancy.

Question 6

At the end of the first trimester, what can be found?

Answer 6

At the end of the first trimester, all major systems are developed.

Question 7

At the end of the second trimester what can be found?

Answer 7

In the second trimester due to the size of the fetus is easy to visualize details of the fetus with high- resolution real-time ultrasonography, and detect fetal anomalies.

Question 8

At what age and weight is considered fetal maturity? Also, if born at this time will the fetus usually survive?

Answer 8

The fetus reaches a major developmental landmark at 35 weeks of gestation. It weighs approximately 2500 g, which is used to define the level of fetal maturity. If born around this time the fetus usually survives.

Question 9

What structures are used to determine the gestational age using an ultrasound? (5)

Answer 9

• BPD. Biparietal diameter.
• Head circumference.
• Abdominal circumference
• Femur length
• Foot length

Question 10

What disease shows a weight that often exceeds values considered normal for CRL?

Answer 10

Gestational diabetes

Question 11

What are characteristics of a freshly expelled fetus versus one that has been dead for several days?

Answer 11

Freshly expelled fetuses have a shiny translucent appearance; those that have been dead for several days before spontaneous abortion have a tanned appearance and lack normal resilience.

Question 12

At the beginning of the ninth week, the head is half the size of what? What are some features of 9 week development?

Answer 12

the crown-heel length of the fetus

Face is broad, eyes are widely separated, ears are low set, and eyelids are fused

Question 13

Growth in body length is fast so by the end of 12 weeks, what doubles?

Answer 13

CRL

Question 14

At 38 weeks the head represents what percentage of the total length of the body?

Answer 14

25% or 1/4

Question 15

Primary ossification centers appear by the end of 12 weeks where?

Answer 15

Cranium and Long Bones

Question 16

1. Early in what week can you find the legs are short and the thighs are small.
2. By what week will you find the upper limbs reach their final length; the lower limbs are not so well developed and are slightly shorter than their final relative length.

Answer 16

Week 9 and Week 12

Question 17

At what week are you able to distinguish between a male and female based on genitalia?

Answer 17

External genitalia of males and females are similar until the end of the week 9, at week 12 they will reach their mature fetal form.

Question 18

By the end of which week the intestines return back to the abdomen?

Answer 18

Intestinal coils are clearly visible in the proximal end of the umbilical cord until the middle of week 10. By the end of the week 11 the intestines return to the abdomen.

Question 19

What is the major site for erythropoiesis in week 9? What is the major erythropoietic organ at the end of week 12?

Answer 19

At week 9, the liver is the major site of erythropoiesis (formation of red blood cells ). By the end of week 12 the spleen is the main erythropoietic organ.

Question 20

Urine formation begins between what weeks?

Answer 20

Urine formation begins between week 9 and 12, and urine is discharged through the urethra into the amniotic fluid.

Question 21

Between 9 and 12 week the fetus starts reabsorbing some amniotic fluid after swallowing it. Fetal waste products are transferred to the maternal circulation by passing across what membrane?

Answer 21

Placental

Question 22

At week 14 movements cannot be felt by the mother yet, so we use what to see the movements?

Answer 22

The body of the embryo grows fast. Limb movements become coordinated by
week 14, but are not felt by the mother yet. The movements are visible during **ultrasounds. **

Question 23

At week 17, what are the fetal movements felt by the mother called? What is the cheeselike material that covereds the skin? What does it consist of?

Answer 23

The fetus increases its CRL by about 50 mm. Fetal movements,
called quickening, are felt by the mother. The skin is covered
with a greasy, cheeselike material, the vernix caseosa. It consists of
a mixture of dead epidermal cells and secretion from sebaceous glands

Question 24

What is the purpose of vernix caseosa? What holds the vernix caseosa onto the skin> What kind of adipose tissue develops during this period?

Question 25

What is the surface active lipid that maintains the patency of the developing alveoli of the lungs? What is responsible for the secretion of this lipid?

Answer 25

The skin is wrinkled and translucent. At 21 weeks, rapid eye have surfactant, a surface- active lipid that maintains the patency of the developing alveoli of the lungs. It is secreted by type II pneumocytes, and they start by week 24.

Question 26

Week 26- Week 29

1. Fetuses born at what age will survive if given intensive care?
2. The lung’s pulmonary vasculature provide what?
3. What nervous system can direct rhythmic breathing and control body temperature?
4. The fetal spleen becomes an important site for what process at week 26?
5. What becomes the major site by the end of week 28?

Answer 26

1. 26 weeks.
2. Adequate gas exhange
3. Central
4. Erthropoiesis
5. Bone Marrow

Question 27

What are characteristics of a fetus at week 26?

Question 28

The pupillary light reflex of the eyes is present at 30 weeks. The skin is pink, the limbs have a chubby appearance. At this age the quantity of white fat is about what percentage of body weight?

Answer 28

8%

Question 29

The pupillary light reflex of the eyes is present at 30 weeks. The skin is pink, the limbs have a chubby appearance. At this age the quantity of white fat is about what percentage of body weight?

Answer 29

8%

Question 30

By full term fetuses normally reach a CRL of ______ mm and weigh about ___\__g?

By 36 weeks, circumferences of head and abdomen are almost equal. The fetal foot measurement is slightly larger than femoral length at 37 weeks. By full term fetuses normally reach a CRL of 360 mm and weigh about 3400 g. White fat is about 16% of body weight. Male fetuses generally are larger and weigh more than female fetuses. Testes are usually in the scrotum in full-term male infants, premature

infants have undescended testes.

Answer 30

By 36 weeks, circumferences of head and abdomen are almost equal. The fetal foot measurement is slightly larger than femoral length at 37 weeks. By full term fetuses normally reach a CRL of 360 mm and weigh about 3400 g. White fat is about 16% of body weight. Male fetuses generally are larger and weigh more than female fetuses. Testes are usually in the scrotum in full-term male infants, premature

infants have undescended testes.

Question 31

W

Question 32

What is the difference between a full term low weight birth and a premature baby?

Answer 32

Premature babies are less than 37 weeks which means they are not full term.

Question 33

What are some main factors due to Intrauterine Growth Restriction?

Answer 33

• Placental Insufficiency
• Multiple gestations
• Infectious Diseases
• Cardiovascular anomalies
• Inadequate maternal nutrition.

Also by teratogens such as

• alcohol
• drugs
• chemicals
• viruses

Question 34

What is the primary source of energy for fetal metabolism and growth? What is the secondary source? Insulin is required to metabolize the primary source of energy and it is secreted by what organ?

Answer 34

Glucose is a primary source of energy for fetal metabolism and growth; aminoacids are also important. Insulin required for the metabolism of glucose is secreted by the fetal pancreas, no maternal insulin passes through the placenta.

Question 35

What are the factors taht affect prenatal growth?

Answer 35

Factors affecting prenatal growth:

• Maternal
• Fetal
• Environmental

Question 36

The growth rate for fetuses from smoking mothers is less than normal during the last 6 to 8 weeks.

When adequate care is unavailable perinatal morbidity increases, decreases, or stays the same?

Answer 36

Increases

Question 37

IUGR is presented as a part of what? The use of marijuana and other illicit drugs can cause obstetrics complications.

Answer 37

Fetal Alcohol Syndrome (FAS)

Question 38

What are 3 conditions that the maternal placental circulation may be reduced by that decreases uterine blood flow?

Answer 38

small chorionic vessels, severe maternal hypothension and renal disease

Question 39

A woman in the 20th week of a high-risk pregnancy was scheduled for a repeat cesarean section. Her physician wanted to establish an expected date of delivery.

1. How would an expected date of delivery be established?
2. When would labor likely be induced?
3. How could this be accomplished?

Answer 39

Physicians cannot always rely on information about the time of the LNMP provided by their patients, especially in cases in which determination of fertilization age is extremely important; for example, in high-risk pregnancies in which one might wish to induce labor as soon as possible. One can determine with reasonable accuracy the estimated date of confinement, or expected date of delivery using diagnostic ultrasonography to estimate the size of the fetal head and abdomen. Normally labor would be induced after 36 to 37 weeks, using hormones (e.g., prostaglandins and oxytocin), unless there is a good reason to do so earlier.

Question 40

A 44-year-old pregnant woman was worried that she might be carrying a fetus with major birth defects.

1. How could the status of her fetus be determined?
2. What chromosomal abnormality would most likely be found?
3. What other chromosomal aberrations might be detected?
4. If this was of clinical interest, how could the sex of the fetus be determined in a family known to have hemophilia or muscular dystrophy?

Answer 40

CVS (chorionic villus sampling) would likely be performed for study of the fetus’s chromosomes. The most common chromosomal disorder detected in fetuses of women older than 40 years of age is trisomy 21. If the chromosomes of the fetus were normal, but birth defects of the brain or limbs were suspected, ultrasonography would likely be performed. These methods allow one to look for morphologic abnormalities while scanning the entire fetus. The sex of the fetus could be determined by examining the sex chromosomes in cells obtained by CVS. One can often determine fetal sex using ultrasonography.

Question 41

A 19-year-old woman in the second trimester of pregnancy asked a physician whether her fetus was vulnerable to over-the-counter drugs and street drugs. She also wondered about the effect of her heavy drinking and cigarette smoking on her fetus.

1. What would the physician likely tell her?

Answer 41

There is considerable danger when uncontrolled drugs (over-the-counter drugs) such as aspirin and cough medicines are consumed excessively or indiscriminately by pregnant women. Withdrawal seizures have been reported in infants born to mothers who are heavy drinkers, and fetal alcohol syndrome is present in some of these infants (see Chapter 20). The physician would likely tell the patient not to take any drugs that are not prescribed. Drugs that are most detrimental to her fetus are under legal control and are dispensed with great care.

Question 42

An ultrasound examination of a pregnant woman revealed IUGR of the fetus.

• What factors may cause IUGR? Discuss them.
• Which factors can the mother eliminate?

Answer 42

Many factors (fetal, maternal, and environmental) may reduce the rate of fetal growth (IUGR). Examples of such factors are intrauterine infections, multiple pregnancies, and chromosomal abnormalities. Cigarette smoking, narcotic addiction, and consumption of large amounts of alcohol are also well-established causes of IUGR. A mother interested in the growth and general well-being of her fetus consults her doctor frequently, eats a good-quality diet, and does not use illicit drugs, smoke, or drink alcohol.

Question 43

A woman in the first trimester of pregnancy who was to undergo amniocentesis expressed concerns about a miscarriage and the possibility of injury to her fetus.

1. What are the risks of these complications?
2. What procedures are used to minimize these risks?
3. What other technique might be used for obtaining cells for chromosomal study?
4. What does the acronym PUBS stand for?
5. Describe how this technique is performed and how it is used to assess the status of a fetus.

Answer 43

Amniocentesis is relatively devoid of risk. The chance of inducing an abortion is estimated to be approximately 0.5%. CVS can also be used for obtaining cells for chromosome study. PUBS refers topercutaneous umbilical cord blood sampling. The needle is inserted into the umbilical vein with the guidance of ultrasonography. Chromosome and hormone studies can be performed on this blood.

Question 44

A pregnant woman is told that she is going to have an AFP test to determine whether there are any fetal anomalies.

1. What types of fetal anomalies can be detected by an AFP assay of maternal serum? Explain.
2. What is the significance of high and low levels of AFP?

Answer 44

Neural tube defects are indicated by high levels of alpha fetoprotein (AFP). Diagnostic studies would be done monitoring the levels of AFP. Further studies would be done using ultrasonography. Low levels of AFP may indicate Down syndrome.Chromosome studies maybe done to check the chromosome complement of the fetal cells.

Question 45

What is the decidua capsularis?

Answer 45

B

The decidua capsularis is the part of the decidua (gravid endometrium) that encapsulates the luminal surface of the implanted conceptus. At the stage shown, it is fused with the smooth chorion (chorion laeve). Together the amnion and chorion form the amniochorionic me

Question 46

What ensheaths the umbilical cord?

Answer 46

D

As the amniotic sac enlarges, it obliterates the chorionic cavity and ensheaths the umbilical cord. The amnion becomes the epithelial covering of the cord.

Question 47

A couple returns to your clinic quite distressed after their 9-week fetal ultrasound. During the examination, the father thought he could see the fetus’ penis on the ultrasound, but was told that it was not clear whether the fetus was a male or female on this basis. That parents are now concerned that their child may have a congenital defect of the genitalia. You explain to the parents that:

A. At this stage, the normal fetus has sex-indistinguishable genitalia

B. This sign is a significant concern and that you need to order genetic testing

C. Only the clitoris would be visible at this stage

D. The father did see the definitive penis, but the ultrasonographer is not allowed to report the gender

E. The definitive genitalia are formed only by 22 weeks

Answer 47

A. At this stage, the normal fetus has sex-indistinguishable genitalia

The normal development of the genitalia continues into the fetal period, and by 12 weeks they have differentiated completely.

Question 48

You are on obstetric call and a woman is brought to the ward in labor. She has received no prenatal care, and up to 3 months ago did not think she was pregnant. You deliver an infant female weighing 2200g, with wrinkled skin and little subcutaneous fat. This infant:

A. Must be preterm
B. Is a normal weight for a full-term pregnancy
C. May be full term and suffering from intrauterine growth retardation (IUGR)
D. Must be a twin
E. Likely has a mother with poorly controlled diabetes mellitus

Answer 48

C. May be full term and suffering from IUGR.

IUGR may be the result of a variety of factors such as placental insufficiency, infection, poor maternal nutrition, and teratogens. The infant typically presents with wrinkled skin and little subcutaneous fat.

Question 49

A 40-year-old woman is admitted for induction of labor. She calculated her delivery date to be 3 weeks ago based on conception. Her menstrual cycle was very irregular and at the neighborhood clinic she was given an estimated deliver date for 1 week ago. She has six cats as pets and smoked one-half pack of cigarettes every day. At birth the infant demonstrated dry parchment-like skin, long nails, no lanugo, and weighed 4000g. The infant was obviously suffering from:

A. Postmaturity syndrome
B. Intrauterine growth retardation (IUGR)
C. The effects of maternal toxoplasmosis
D. The typical effects seen when a mother smokes during pregnancy
E. Nothing abnormal: all these characteristics are normal for a full-term pregnancy

Answer 49

Postmaturity syndrome

All these characteristics are seen in postmaturity syndrome, as well as decreased or absent vernix caseosa and increased alertness.