Embedded Files
"A Human Embryo in the Seventh Week of Pregnancy" by Ed Uthman, MD. used under CC BY SA 2.0/Cropped from original
Changes During Pregnancy.pdfAmerican College of Obstetrics and Gynecology (2020, October). Changes During Pregnancy. https://www.acog.org/womens-health/infographics/changes-during-pregnancy
Placenta
Placenta
The placenta is completely formed by 12 weeks of gestation. Its major function is to transfer substances such as oxygen, carbon dioxide, and nutrients. It also has endocrine functions and supplies the mother with four hormones that are necessary to maintain pregnancy: human chorionic gonadotropin (hCG), human placental lactogen (hPL), progesterone, and estrogen. Adequate maternal circulation is essential to maintain the function of the placenta, and any compromise to the mother’s circulation will impact the ability to nourish the fetus.
Kahn Academy (2014, November 25). Meet the Placenta: https://www.youtube.com/watch?v=bQioHx12JuY
Photo By: Cmglee - https://en.wikipedia.org/wiki/Fetal_circulation, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=123131034
Fetal Side of Placenta
Known as the "Shiny Schultz" side, you can see vessels coming from different areas of the placenta to the umbilical cord.
"Human Placenta Just After Delivery" by Grendelkhan, used under CC BY SA 4.0/Cropped from original
Amniotic Sac on Placenta
Shown being held up and away from the fetal side of the placenta, it surrounds the fetus in the uterus and is filled with amniotic fluid.
"A Human Placenta Immediately After the Birth of a Child" by Donald Trung used under CC BY SA 4.0/Cropped from original
Maternal Side of Placenta
Known as the "Dirty Duncan" side, you can see the lobes that are attached to the uterus and are derived from the decidua basalis. Amniotic sac can be seen gathered at the top of the image.
"Maternal Side of a Whole Human Placenta, Just After Birth" by أمينused under CC BY SA 4.0/Cropped from original
The Embryo and Fetus
The Embryo and Fetus
The embryo has three primary germ layers: the ectoderm (which becomes epidermal tissue, nervous tissue, and eyes), the mesoderm (which becomes the skin, muscles, and connective tissues), and the endoderm (which becomes the digestive tract, respiratory tract, liver, pancreas, and urogenital organs). The embryonic period lasts from day 15 to approximately 8 weeks after conception (10 weeks after the LMP). This is the most critical time of fetal development as the organs of the body are being formed. At this point, known as organogenesis, exposure to any medications, chemicals, infections, or toxins that are teratogenic (harmful to the baby) may cause the malformation of whichever organ is being formed at that particular time. After approximately 9 weeks from conception (11 weeks after the LMP), the baby is known as a fetus. Viability is a term used to describe the time the baby can live outside the womb either with or without ventilatory support. Generally speaking, this occurs by approximately 24 weeks of gestation.
There are two fetal membranes that surround the developing embryo: the chorion and the amnion. The chorion contains the chorionic villi, which burrow into the decidua as described above. The amnion forms the fluid-filled amniotic sac as well as the covering of the umbilical cord, and it covers the chorion on the fetal side. Amniotic fluid is produced by fetal urine and serves to cushion the fetus from trauma and outside forces plus prevent pressure on the umbilical cord. The volume of amniotic fluid is important. If a baby has too little amniotic fluid, it is known as oligohydramnios; it compromises the protection of the fetus and also may indicate kidney malfunctioning or poor placental blood flow. Too much amniotic fluid is called polyhydramnios (or simply hydramnios) and may occur when a mother has diabetes or there is a disruption in the baby’s ability to swallow the fluid.
"Germ Layers of the Embryo" by Rice University used under CC BY SA 4.0/Cropped from original
Kahn Academy (2014, October 24). Germ Layer Derivatives: https://www.youtube.com/watch?v=QPvhl66QCqo
Ultrasound of fetus at 9 week gestation
"Movements of a Human Embryo of a Gestational Age of Almost Exactly 9 Weeks" by Mikael Häggström used under CC BY SA 2.0/Cropped from original
"Colorized Version of Original Artwork by Henry VanDyke Carter from Gray's Anatomy by Henry Gray" by Denns M DePace, PhD used under CC BY SA 4.0 /Cropped from original
How Possible (2017, July 13). Fetal Development: https://www.youtube.com/watch?v=WtDknjng8TA
Cross Section of Umbilical Cord
"A Histological Cross Section of the Umbilical Cord Showing the Umbilical Cord Lining Membrane" by Johnlancer123 used under CC BY SA 3.0/Cropped from original
While an embryo, nutrition is supplied via the yolk sac; once placental blood flow is established, oxygen and nutrients are provided via diffusion from the maternal vessels of the placenta through the chorionic villi to the baby. This is transported to the developing fetus through the umbilical cord. The umbilical cord is made up of two arteries and one vein. The arteries bring oxygenated blood and waste products from the fetus to the placenta, where the mother’s blood can collect it and get rid of it. The vein will bring oxygenated blood and nutrients from the placenta to the fetus. The vessels in the umbilical cord are surrounded by a thick substance called Wharton’s jelly, which helps maintain blood flow by minimizing compression of the vessels. The term nuchal cord is used when the umbilical cord is wrapped around the baby’s neck. It is a common finding and, although it sounds harmful, in actuality it is not, as the fetus is not breathing and oxygen is provided through the umbilical cord. However, the blood flow in the cord can be cut off if it is wrapped too tightly around any part of the baby’s body or compressed in any way. Reassurance to the parents may be necessary if they find that the umbilical cord is wrapped around the neck.
National Library of Medicine (2021, March 1). Mother to Baby (Fact Sheet). https://www.ncbi.nlm.nih.gov/books/NBK582659/
The Fetal Circulatory System
The Fetal Circulatory System
The fetal heart has a few adjustments to help the baby sustain life in utero without breathing through the lungs: the ductus venosus, the ductus arteriosus, and the foramen ovale. Blood flows from the umbilical vein to the ductus venosus and then to the inferior vena cava and onward to the right atrium. Once in the right atrium, some blood flows to the pulmonary artery and some goes through the foramen ovale to the left atrium. Blood that goes to the right ventricle will go to the pulmonary arteries. Due to the high pressure in the fluid-filled lungs, the blood will mostly flow through the ductus arteriosus to the aorta to be brought to the rest of the body. The blood returns to the placenta through the umbilical arteries. Note that this is the only time that oxygenated blood flows through a vein and deoxygenated blood flows through arteries. Once the baby is delivered and the umbilical cord is cut, systemic vascular resistance rises and pulmonary pressure decreases with the expulsion of lung fluid. Blood no longer will flow through the foramen ovale or the ductus arteriosus; these will usually close completely after a few months.
McCabe, L. (2021, March 16). Fetal Circulation. Open Pediatrics
"Diagram of Circulation After Birth" Photo by Cooke, Joseph Brown, used under CC BY SA 4.0/Cropped from original
"Fetal Circulatory System" by OpenStax College - Anatomy & Physiology, Connexions Web site used under CC BY SA 3.0/Cropped from original
Fetal Respiratiory System
Fetal Respiratiory System
Lung size is often used an evaluation of gestational age for a baby. Fetal lungs develop between weeks 3-7 and consists of bronchia and the diaphragm. Small lung buds develop around the fifth week which will eventually become the lung lobes: two on the left and three on the right. By the 17th week, a respiratory tree has developed which includes bronchioles, arterial systems, cartilage, and smooth muscle, but gas exchange cannot occur yet.
Generally speaking babies born after 24 weeks can survive with significant respiratory support which decreases as their gestational age advances; common examples of respiratory support include ventilatory support, CPAP to alleviate episodes of apnea, or oxygen supplementation. 24 weeks marks the stage where the surface area of the lungs expands and saccules form allowing for gas exchange. Surfactant begins to be produced, however it is not enough to prevent atelectasis; this occurs around 32 weeks gestation. Women who threaten to deliver prematurely are given the steroid betamethasone to help mature the lungs and increase surfactant; this may be repeated if the mother does not deliver her fetus.
By 36 weeks the number and size of alveoli increases to where the lungs are mature enough for the infant to survive outside without respiratory support.
Avena-Zampieri, C.L, Hutter, J., Rutherford, M., Greenough, A., & Story, L. (2022, September). Assessment of the Fetal Lungs In Utero, 4(5). doi: https://www.ajogmfm.org/article/S2589-9333(22)00125-2/fulltext
Let's Practice!: Fetal Development
Let's Practice!: Fetal Development
Answer the following questions about fetal development to check your knowledge.
What is the duration for which the sperm remains viable in the female reproductive system?
What is the duration for which the sperm remains viable in the female reproductive system?
2 to 4 days after intercourse
3 to 5 days after intercourse
4 to 8 days after intercourse
5 to 9 days after intercourse
Answer: 2
The sperm remains viable in the female reproductive system for 3 to 5 days after sexual intercourse. Within this time a sperm fuses with an ova to form a zygote.
The sperm is no longer viable after 5 days. Therefore they do not remain viable after 4 to 8, and 5 to 9 days after intercourse.
A woman at 35 weeks of gestation has had an amniocentesis. The results reveal that surface-active phospholipids are present in the amniotic fluid. The nurse is aware that this finding indicates:
A woman at 35 weeks of gestation has had an amniocentesis. The results reveal that surface-active phospholipids are present in the amniotic fluid. The nurse is aware that this finding indicates:
The fetus is at risk for Down syndrome.
The woman is at high risk for developing preterm labor.
Lung maturity.
Meconium is present in the amniotic fluid.
Answer: 3
The detection of the presence of pulmonary surfactants (surface-active phospholipids) in amniotic fluid has been used to determine fetal lung maturity, or the ability of the lungs to function after birth. This occurs at approximately 35 weeks of gestation.
The presence of surface-active phospholipids is not an indication of Down syndrome.
This result reveals the fetal lungs are mature and in no way indicates risk for preterm labor.
Meconium should not be present in the amniotic fluid.
The student nurse is giving a presentation about milestones in embryonic development. Which information should the student include?
The student nurse is giving a presentation about milestones in embryonic development. Which information should the student include?
At 8 weeks of gestation, primary lung and urethral buds appear
At 12 weeks of gestation, the vagina is open or the testes are in position for descent into the scrotum.
At 20 weeks of gestation, the vernix caseosa and lanugo appear.
At 24 weeks of gestation, the skin is smooth, and subcutaneous fat is beginning to collect.
Answer: 3
Two milestones that occur at 20 weeks are the appearance of the vernix caseosa and lanugo.
The primary lung and urethral buds appear at 6 weeks of gestation.
The vagina is open or the testes are in position for descent into the scrotum at 16 weeks.
The appearance of smooth skin occurs at 28 weeks, and subcutaneous fat begins to collect at 30 to 31 weeks.
How many veins and arteries are present between the maternal and the fetal circulatory system by the fifth week of pregnancy?
How many veins and arteries are present between the maternal and the fetal circulatory system by the fifth week of pregnancy?
One vein and one artery
Two veins and one artery
One vein and two arteries
Two veins and two arteries
Answer: 3
The fetal heart starts beating by the end of the fifth week.
Two arteries carry blood from the embryo to the chorionic villi, and one vein returns the blood to the embryo.
Deoxygenated blood leaves the fetus through the umbilical arteries and enters the placenta, where it is oxygenated. Oxygenated blood leaves the placenta through the umbilical vein, which enters the fetus via the umbilical cord.
It is rare for there to be one vein and one artery. Approximately 1% of umbilical cords contain only two vessels: one artery and one vein. This occurrence is sometimes associated with congenital malformations.
Therefore the presence of two veins and one artery and two veins and two arteries is inappropriate.
A woman asks the nurse, "What protects my baby's umbilical cord from being squashed while the baby's inside of me?" The nurse's best response is:
A woman asks the nurse, "What protects my baby's umbilical cord from being squashed while the baby's inside of me?" The nurse's best response is:
"Your baby's umbilical cord is surrounded by connective tissue called Wharton jelly, which prevents compression of the blood vessels and ensures continued nourishment of your baby."
"Your baby's umbilical floats around in blood anyway."
"You don't need to worry about things like that."
"The umbilical cord is a group of blood vessels that are very well protected by the placenta."
Answer: 1
"Your baby's umbilical cord is surrounded by connective tissue called Wharton jelly, which prevents compression of the blood vessels and ensures continued nourishment of your baby" is the most appropriate response. "Your baby's umbilical floats around in blood anyway" is inaccurate. "You don't need to worry about things like that" is not appropriate response. It negates the client's need for teaching and discounts her feelings. The placenta does not protect the umbilical cord. The cord is protected by the surrounding Wharton jelly.
The _____ is/are responsible for oxygen and carbon dioxide transport to and from the maternal bloodstream.
The _____ is/are responsible for oxygen and carbon dioxide transport to and from the maternal bloodstream.
Decidua basalis
Blastocyst
Germ layer
Chorionic villi
Answer: 4
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 of 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.
Sally comes in for her first prenatal examination. This is her first child. She asks you (the nurse), "How does my baby get air inside my uterus?" The correct response is:
Sally comes in for her first prenatal examination. This is her first child. She asks you (the nurse), "How does my baby get air inside my uterus?" The correct response is:
"The baby's lungs work in utero to exchange oxygen and carbon dioxide."
"The baby absorbs oxygen from your blood system."
"The placenta provides oxygen to the baby and excretes carbon dioxide into your bloodstream."
"The placenta delivers oxygen-rich blood through the umbilical artery to the baby's abdomen."
Answer: 3
The placenta functions by supplying oxygen and excreting carbon dioxide to the maternal bloodstream.
The fetal lungs do not function for respiratory gas exchange in utero.
The baby does not simply absorb oxygen from a woman's blood system.
Blood and gas transport occur through the placenta. The placenta delivers oxygen-rich blood through the umbilical vein and not the artery.
The most basic information a maternity nurse should have concerning conception is that:
The most basic information a maternity nurse should have concerning conception is that:
Ova are considered fertile 48 to 72 hours after ovulation.
Sperm remain viable in the woman's reproductive system for an average of 12 to 24 hours.
Conception is achieved when a sperm successfully penetrates the membrane surrounding the ovum.
Implantation in the endometrium occurs 6 to 10 days after conception.
Answer: 4
After implantation, the endometrium is called the decidua.
Ova are considered fertile for about 24 hours after ovulation.
Sperm remain viable in the woman's 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.
A maternity nurse should be aware of which fact about the amniotic fluid?
A maternity nurse should be aware of which fact about the amniotic fluid?
It serves as a source of oral fluid and a repository for waste from the fetus.
The volume remains about the same throughout the term of a healthy pregnancy.
A volume of less than 300 ml is associated with gastrointestinal malformations.
A volume of more than 2 L is associated with fetal renal abnormalities.
Answer: 1
Amniotic fluid serves as a source of oral fluid, a repository for waste from the fetus, and also cushions the fetus and helps maintain a constant body temperature.
The volume of amniotic fluid changes constantly.
Too little amniotic fluid (oligohydramnios) is associated with renal abnormalities.
Too much amniotic fluid (hydramnios) is associated with gastrointestinal and other abnormalities.
With regard to the structure and function of the placenta, the maternity nurse should be aware that:
With regard to the structure and function of the placenta, the maternity nurse should be aware that:
As the placenta widens, it gradually thins to allow easier passage of air and nutrients.
As one of its early functions, the placenta acts as an endocrine gland.
The placenta is able to keep out most potentially toxic substances such as cigarette smoke to which the mother is exposed.
Optimal blood circulation is achieved through the placenta when the woman is lying on her back or standing.
Answer 2
The placenta produces four hormones necessary to maintain the pregnancy.
The placenta widens until week 20 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.
With regard to the development of the respiratory system, maternity nurses should be aware that:
With regard to the development of the respiratory system, maternity nurses should be aware that:
The respiratory system does not begin developing until after the embryonic stage.
The infant's lungs are considered mature when the lecithin/sphingomyelin (L/S) ratio is 1:1, at about 32 weeks.
Maternal hypertension can reduce maternal-placental blood flow, accelerating lung maturity.
Fetal respiratory movements are not visible on ultrasound scans until at least 16 weeks.
Answer 3
A reduction in placental blood flow stresses the fetus, increases blood levels of corticosteroids, and thus accelerates lung maturity.
Development of the respiratory system begins during the embryonic phase and continues into childhood.
The infant's lungs are mature when the L/S ratio is 2:1, at about 35 weeks.
Lung movements have been seen on ultrasound scans at 11 weeks.
The nurse caring for a pregnant client knows that her health teaching regarding fetal circulation has been effective when the client reports that she has been sleeping:
The nurse caring for a pregnant client knows that her health teaching regarding fetal circulation has been effective when the client reports that she has been sleeping:
In a side-lying position.
On her back with a pillow under her knees.
With the head of the bed elevated.
On her abdomen.
Answer: 1
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, thereby enhancing blood flow to the fetus. However, it is now known that either side-lying position enhances uteroplacental blood flow. If a woman lies on her back with the pressure of the uterus compressing the vena cava, blood return to the right atrium will be diminished.
Although this position is recommended and ideal for later in pregnancy, the woman must still maintain a lateral tilt to the pelvis to avoid compression of the vena cava.
Each of the following structures plays a critical role in fetal growth and development. DESCRIBE the functions of these structures.
Yolk sac
Amniotic fluid and membranes
Umbilical cord
Placenta
Other Resources
Other Resources
American College of Obstetricians and Gynecologists (2017, August). Committee Opinion Number 713: Antenatal Therapy for Fetal Lung Maturation. https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/08/antenatal-corticosteroid-therapy-for-fetal-maturation#:~:text=Administration%20of%20betamethasone%20may%20be,previous%20course%20of%20antenatal%20corticosteroids.
Avena-Zampieri, C.L, Hutter, J., Rutherford, M., Greenough, A., & Story, L. (2022, September). Assessment of the Fetal Lungs In Utero, 4(5). doi: https://www.ajogmfm.org/article/S2589-9333(22)00125-2/fulltext
Donovan, M.F. and Cascella, M. (2022, October 10). Embryology, Weeks 6-8. https://www.ncbi.nlm.nih.gov/books/NBK563181/
Falck, A. (2018, January 12). The Five Stages of Fetal Lung Development [Video]. YouTube. https://www.youtube.com/watch?v=-jjvBNNMY0A
National Library of Medicine (2021, March 1). Mother to Baby (Fact Sheet). https://www.ncbi.nlm.nih.gov/books/NBK582659/
Rehman, S., Bacha, D. (2023, August 14). Embryology, Pulmonary. https://www.ncbi.nlm.nih.gov/books/NBK544372/
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