Ch 12: Conception and Fetal Development

A newly married couple plans to use the natural family planning method of contraception. Understanding how long an ovum can live after ovulation is important to them. The nurse knows that his or her teaching was effective when the couple responds that an ovum is considered fertile for which period of time?

24 hours Most ova remain fertile for approximately 24 hours after ovulation, much longer than 6 to 8 hours. However, ova do not remain fertile for 2 to 3 days or are viable for 1 week. If unfertilized by a sperm after 24 hours, the ovum degenerates and is reabsorbed.

Some of the embryos intestines remain within the umbilical cord during the embryonic period. What is the rationale for this development of the gastrointestinal system?

Abdomen is too small to contain all the organs while they are developing. The abdominal contents grow more rapidly than the abdominal cavity; therefore, part of their development takes place in the umbilical cord. By 10 weeks of gestation, the abdomen is large enough to contain them. Intestines begin their development within the umbilical cord but only because the liver and kidneys occupy most of the abdominal cavity. Blood supply is adequate in all areas.

A woman in labor passes some thick meconium as her amniotic fluid ruptures. The client asks the nurse where the baby makes the meconium. What is the correct response by the nurse?

Fetal intestines As the fetus nears term, fetal waste products accumulate in the intestines as dark green-to-black, tarry meconium. Meconium is not produced by the fetal kidneys nor should it be present in the amniotic fluid, which may be an indication of fetal compromise. The placenta does not produce meconium.

Relating to the fetal circulatory system, which special characteristics allow the fetus to obtain sufficient oxygen from the maternal blood? (Select all that apply.)

- Fetal hemoglobin (Hb) carries 20% to 30% more oxygen than maternal Hb. - Hb concentration is 50% higher than that of the mother. - Fetal heart rate is 110 to 160 beats per minute. The following three special characteristics enable the fetus to obtain sufficient oxygen from maternal blood: (1) the fetal Hb carries 20% to 30% more oxygen; (2) the concentration is 50% higher than that of the mother; and (3) the fetal heart rate is 110 to 160 beats per minute, a cardiac output that is higher than that of an adult.

The measurement of lecithin in relation to sphingomyelin (lecithin/sphingomyelin [L/S] ratio) is used to determine fetal lung maturity. Which ratio reflects fetal maturity of the lungs?

2:1 The L/S ratio indicates a 2:1 ratio of lecithin to sphingomyelin, which is an indicator of fetal lung maturity and occurs at approximately the middle of the third trimester. L/S ratios of 1.4:1, 1.8:1, and 1:1 each indicate immaturity of the fetal lungs.

Which information regarding amniotic fluid is important for the nurse to understand?

Amniotic fluid serves as a source of oral fluid and a repository for waste from the fetus. Amniotic fluid serves as a source of oral fluid, serves as a repository for waste from the fetus, cushions the fetus, and helps maintain a constant body temperature. The volume of amniotic fluid constantly changes. The study of amniotic fluid yields information regarding the sex of the fetus and the number of chromosomes. Too much amniotic fluid (hydramnios) is associated with gastrointestinal and other abnormalities.

A woman who is 16 weeks pregnant asks the nurse, Is it possible to tell by ultrasound if the baby is a boy or girl yet? What is the best answer?

The baby has developed enough to enable us to determine the sex by examining the genitals through an ultrasound scan. Although gender is determined at conception, the external genitalia of males and females look similar through the ninth week. By the twelfth week, the external genitalia are distinguishable as male or female.

The pancreas forms in the foregut during the 5th to 8th week of gestation. A client with poorly controlled gestational diabetes asks the nurse what the effects of her condition will be on the fetus. What is the best response by the nurse? Poorly controlled maternal gestational diabetes will:

result in a macrocosmic fetus. Insulin is produced by week 20 of gestation. In the fetus of a mother with uncontrolled diabetes, maternal hypoglycemia produces fetal hypoglycemia and macrocosmia results. Hyperinsulinemia blocks lung maturation, placing the neonate at risk for respiratory distress.

What kind of fetal anomalies are most often associated with oligohydramnios?

Renal An amniotic fluid volume of less than 300 ml (oligohydramnios) is often associated with fetal renal anomalies. The amniotic fluid volume has no bearing on the fetal cardiovascular system. Gastrointestinal anomalies are associated with hydramnios or an amniotic fluid volume greater than 2 L. The amniotic fluid volume has no bearing on the fetal neurologic system.

Which statement regarding the structure and function of the placenta is correct?

Secretes both estrogen and progesterone As one of its early functions, the placenta acts as an endocrine gland, producing four hormones necessary to maintain the pregnancy and to support the embryo or fetus: human chorionic gonadotropin (hCG), human placental lactogen (hPL), estrogen, and progesterone. The placenta does not produce nutrients. It functions as a means of metabolic exchange between the maternal and fetal blood supplies. Many bacteria and viruses can cross the placental membrane.

A client arrives for her initial prenatal examination. This is her first child. She asks the nurse, How does my baby get air inside my uterus? What is the correct response by the nurse?

The placenta provides oxygen to the baby and excretes carbon dioxide into your bloodstream. The placenta delivers oxygen-rich blood through the umbilical vein, not the artery, to the fetus and excretes carbon dioxide into the maternal bloodstream. The fetal lungs do not function as respiratory gas exchange in utero. The baby does not simply absorb oxygen from a womans blood system; rather, blood and gas transport occur through the placenta.

An expectant couple attending childbirth classes have questions regarding multiple births since twins run in the family. What information regarding multiple births is important for the nurse to share?

Twinning and other multiple births are increasing because of the use of fertility drugs and delayed childbearing. If the parents-to-be are older and have taken fertility drugs, then they would be very interested to know about twinning and other multiple births. Conjoined twins are monozygotic; that is, they are from a single fertilized ovum in which division occurred very late. Identical twins show no racial or ethnic preference, and fraternal twins are more common among African-American women. Fraternal twins can be different genders or the same gender, and identical twins are the same gender.

Congenital disorders refer to those conditions that are present at birth. These disorders may be inherited and caused by environmental factors or maternal malnutrition. Toxic exposures have the greatest effect on development between 15 and 60 days of gestation. For the nurse to be able to conduct a complete assessment of the newly pregnant client, he or she should be knowledgeable regarding known human teratogens. Which substances might be considered a teratogen? (Select all that apply.)

- Cytomegalovirus (CMV) - Ionizing radiation - Carbamazepine - Lead Exposure to radiation and a number of infections may result in profound congenital deformities. These include but are not limited to varicella, rubella, syphilis, parvovirus, CMV, and toxoplasmosis. Certain maternal conditions such as diabetes and phenylketonuria (PKU) may also affect organs and other parts of the embryo during this developmental period. Drugs such as antiseizure medications (e.g., carbamazepine) and some antibiotics, as well as chemicals including lead, mercury, tobacco, and alcohol, may also result in structural and functional abnormalities.

At a routine prenatal visit, the nurse explains the development of the fetus to her client. At approximately ____ weeks of gestation, lecithin is forming on the alveolar surfaces, the eyelids open, and the fetus measures approximately 27 cm crown to rump and weighs approximately 1110 g. The client is how many weeks of gestation at todays visit?

28 These milestones in human development occur at 28 weeks of gestation. These milestones have not occurred by 20 or 24 weeks of gestation but have been reached before 30 weeks of gestation.

The maternity nurse is cognizant of what important structure and function of the placenta?

As one of its early functions, the placenta acts as an endocrine gland. The placenta produces four hormones necessary to maintain the pregnancy: hCG, hPL, estrogen, and progesterone. The placenta widens until 20 weeks of gestation and continues to grow thicker. Toxic substances such as nicotine and carbon monoxide readily cross the placenta into the fetus. Optimal circulation occurs when the woman is lying on her side.

A pregnant woman at 25 weeks of gestation tells the nurse that she dropped a pan last week and her baby jumped at the noise. Which response by the nurse is most accurate?

Babies respond to sound starting at approximately 24 weeks of gestation. Babies respond to external sound starting at approximately 24 weeks of gestation. Acoustic stimulations can evoke a fetal heart rate response. There is no such thing as an aural reflex. The last statement is inappropriate and may cause undue psychologic alarm to the client.

The various systems and organs of the fetus develop at different stages. Which statement is most accurate?

Cardiovascular system is the first organ system to function in the developing human. The heart is developmentally complete by the end of the embryonic stage. Hematopoiesis begins in the liver during the sixth week. The body becomes C-shaped at 21 weeks of gestation. The gastrointestinal system is complete at 36 weeks of gestation.

Which structure is responsible for oxygen and carbon dioxide transport to and from the maternal bloodstream?

Chorionic villi Chorionic villi are fingerlike projections that develop out of the trophoblast and extend into the blood-filled spaces of the endometrium. The villi obtain oxygen and nutrients from the maternal bloodstream and dispose carbon dioxide and waste products into the maternal blood. The decidua basalis is the portion of the decidua (endometrium) under the blastocyst where the villi attach. The blastocyst is the embryonic development stage after the morula; implantation occurs at this stage. The germ layer is a layer of the blastocyst.

A womans cousin gave birth to an infant with a congenital heart anomaly. The woman asks the nurse when such anomalies occur during development. Which response by the nurse is most accurate?

Defects occur between the third and fifth weeks of development. The cardiovascular system is the first organ system to function in the developing human. Blood vessel and blood formation begins in the third week, and the heart is developmentally complete in the fifth week. We dont really know when such defects occur is an inaccurate statement. Regardless of the cause, the heart is vulnerable during its period of developmentin the third to fifth weeks; therefore, the statement, They usually occur in the first 2 weeks of development is inaccurate.

Which statement concerning neurologic and sensory development in the fetus is correct?

Fetuses respond to sound by 24 weeks of gestation and can be soothed by the sound of the mothers voice. Hearing develops early and is fully developed at birth. Brain waves have been recorded at week 8. Eyes are receptive to light at 28 weeks of gestation. The fetal brain is approximately one fourth the size of an adult brain.

What is the most basic information that a nurse should be able to share with a client who asks about the process of conception?

Implantation in the endometrium occurs 6 to 10 days after conception. After implantation, the endometrium is called the decidua. Ova are considered fertile for approximately 24 hours after ovulation. Sperm remain viable in the womans reproductive system for an average of 2 to 3 days. Penetration of the ovum by the sperm is called fertilization. Conception occurs when the zygote, the first cell of the new individual, is formed.

Which statement regarding the development of the respiratory system is a high priority for the nurse to understand?

Maternal hypertension can reduce maternal-placental blood flow, accelerating lung maturity. A reduction in placental blood flow stresses the fetus, increases blood levels of corticosteroids, and thus accelerates lung maturity. The development of the respiratory system begins during the embryonic phase and continues into childhood. The infants lungs are considered mature when the L/S ratio is 2:1, at approximately 35 weeks of gestation. Lung movements have been visualized on ultrasound scans at 11 weeks of gestation.

The nurse caring for a pregnant client is evaluating his or her health teaching regarding fetal circulation. Which statement from the client reassures the nurse that his or her teaching has been effective?

Optimal fetal circulation is achieved when I am in the side-lying position. Optimal circulation is achieved when the woman is lying at rest on her side. Decreased uterine circulation may lead to intrauterine growth restriction. Previously, it was believed that the left lateral position promoted maternal cardiac output, enhancing blood flow to the fetus. However, it is now known that the side-lying position enhances uteroplacental blood flow. If a woman lies on her back with the pressure of the uterus compressing the vena cava, then blood return to the right atrium is diminished. Although having the head of the bed elevated is recommended and ideal for later in pregnancy, the woman still must maintain a lateral tilt to the pelvis to avoid compressing the vena cava. Many women find lying on their abdomen uncomfortable as pregnancy advances. Side-lying is the ideal position to promote blood flow to the fetus.

A new mother asks the nurse about the white substance covering her infant. How should the nurse explain the purpose of vernix caseosa?

Vernix caseosa protects the fetal skin from the amniotic fluid. Prolonged exposure to the amniotic fluid during the fetal period could result in the breakdown of the skin without the protection of the vernix caseosa. Normal development of the peripheral nervous system was dependent on nutritional intake of the mother. The amnion was the inner membrane that surrounded the fetus and was not involved in the oxygen and nutrient exchange. The amniotic fluid helped maintain fetal temperature.

Which development related to the integumentary system is correct?

Very fine hairs called lanugo appear at 12 weeks of gestation. Very fine hairs, called lanugo appear first at 12 weeks of gestational age on the fetus eyebrows and upper lip. By 20 weeks of gestation, lanugo covers the entire body. By 20 weeks of gestation the eyelashes, eyebrows, and scalp hair also begin to grow. By 28 weeks of gestation, the scalp hair is longer than these fine hairs, which is thin and may disappear by term. Fingernails and toenails develop from thickened epidermis, beginning during the 10th week. Fingernails reach the fingertips at 32 weeks of gestation, and the toenails reach the toe tips at 36 weeks of gestation.

A woman is 15 weeks pregnant with her first baby. She asks how long it will be before she feels the baby move. What is the nurses best answer?

Within the next month, you should start to feel fluttering sensations. Maternal perception of fetal movement usually begins 16 to 20 weeks after conception. Because this is her first pregnancy, movement is felt toward the later part of the 16- to 20-week time period. Stating, you should have felt the baby move by now is incorrect and may be an alarming statement to the client. Fetal movement should be felt by 16 to 20 weeks. If movement is not felt by the end of that time, then further assessment is necessary.

A woman who is 8 months pregnant asks the nurse, Does my baby have any antibodies to fight infection? What is the most appropriate response by the nurse?

Your baby has IgG and IgM. During the third trimester, IgG is the only immunoglobulin that crosses the placenta; it provides passive acquired immunity to specific bacterial toxins. However, the fetus produces IgM by the end of the first trimester. IgA immunoglobulins are not produced by the baby. Therefore, by the third trimester, the fetus has both IgG and IgM. Breastfeeding supplies the newborn infant with IgA.

A woman asks the nurse, What protects my babys umbilical cord from being squashed while the babys inside of me? What is the nurses best response?

Your babys umbilical cord is surrounded by connective tissue called Whartons jelly, which prevents compression of the blood vessels. Explaining the structure and function of the umbilical cord is the most appropriate response. Connective tissue called Whartons jelly surrounds the umbilical cord, prevents compression of the blood vessels, and ensures continued nourishment of the embryo or fetus. The umbilical cord does not float around in blood or fluid. Telling the client not to worry negates her need for information and discounts her feelings. The placenta does not protect the umbilical cord.