Nursing Care of the Growing Fetus PDF

Nursing Care of the Growing Fetus STAGES OF FETAL DEVELOPMENT In just 38 weeks, a fertilized egg (ovum) matures from a single cell to a fully developed fetus ready to be born. Fetal growth and development can be divided into three time periods: Pre-embryonic (first 2 weeks, beginning w...

Nursing Care of the Growing Fetus STAGES OF FETAL DEVELOPMENT In just 38 weeks, a fertilized egg (ovum) matures from a single cell to a fully developed fetus ready to be born. Fetal growth and development can be divided into three time periods: Pre-embryonic (first 2 weeks, beginning with fertilization) Embryonic (weeks 3 through 8) Fetal (from week 8 through birth)  ZYGOTE: The First Cell in the Human Body OVUM Ovum or egg cell is the female sex gamete. Oogenesis – refers to the development of ovum. Ovum is regularly released by the ovary through the process of ovulation. Sperm cell is present in the fallopian tube only in 3 out of 5 ovulations of married women. It has 2 layers of protective covering: corona radiata-outer layer, zona pellucida-inner layer Egg cell has a lifespan of 24 hours, thus, it can only be fertilized within this period. After 24 hours it regresses and is resorbed. SPERM CELL Sperm cell or spermatozoa is the male sex gamete. Spermatogenesis is the maturation of sperm. It takes about 64 days for sperm cells to attain maturity. It has 3 parts: a head that contain the chromatin materials, a neck or mid-piece that provides energy for movement and a tail that is responsible for its motility. Has a lifespan of 48 to 72 hours or 2 to 3 days after ejaculation.  The sperm must be in the genital tract for 2-3 hours before they can fertilize an ovum to give time for capacitation to occur which includes activating the enzyme hyaluronidase that is needed by the sperm to be able to penetrate the egg cell. There are 2 kinds of sperm cell: 1. Gynosperm – X chromosome carrying sperm cell with large oval head and which produce a female offspring. 2. Androsperm – Y chromosome carrying sperm cells with small head and which produce a male offspring. INSEMINATION Is the deposition of the sperm cell in the female genital tract that occurs during sexual intercourse, or by artificial insemination. Although millions of sperm cells are deposited in the vagina only a few reach the uterus because many of them are destroyed by the acidic vaginal environment. The sperm swims so fast that within 90 seconds it reaches the uterus and is in the fallopian tube within 5 minutes after deposition.  Fertilization: The Beginning of Pregnancy Fertilization (also referred to as conception and impregnation) is the union of an ovum and a spermatozoon. This usually occurs in the outer third of a fallopian tube, termed the ampullar portion (Taylor & Badell, 2011). Usually, only one of a woman’s ova reaches maturity each month. Once the mature ovum is released (i.e., ovulation), fertilization must occur fairly quickly because an ovum is capable of fertilization for only about 24 hours (48 hours at the most). After that time, it atrophies and becomes nonfunctional. Because the functional life of a spermatozoon is also about 48 hours, possibly as long as 72 hours, the total critical time span during which sexual relations must occur for fertilization to be successful is about 72 hours (48 hours before ovulation plus 24 hours afterward). As the ovum is extruded from the graafian follicle of an ovary with ovulation, it is surrounded by a ring of mucopolysaccharide fluid (the zona pellucida) and a circle of cells (the corona radiata). The ovum and these surrounding cells (which increase the bulk of the ovum and serve as protective buffers against injury) are propelled into a nearby fallopian tube by currents initiated by the fimbriae—the fine, hairlike structures that line the openings of the tubes. A combination of peristaltic action of the tube and movements of the tube cilia help propel the ovum along the length of the tube. Normally, an ejaculation of semen averages 2.5 ml of fluid containing 50 to 200 million spermatozoa per milliliter, or an average of 400 million sperm per ejaculation ( Christianson & Wallach, 2011). At the time of ovulation, there is a reduction in the viscosity (thickness) of the woman’s cervical mucus, which makes it easy for spermatozoa to penetrate it. Spermatozoa move through the cervix and the body of the uterus and into the fallopian tube, toward a waiting ovum by the combination of movement by their flagella (tails) and uterine contractions. All of the spermatozoa that reach the ovum cluster around Its protective layer of corona cells. Hyaluronidase (a proteolytic enzyme) is released by the spermatozoa and dissolves the layer of cells protecting the ovum- corona radiata. Under ordinary circumstances, only one spermatozoon is able to penetrate the cell membrane of the ovum. Once it penetrates the cell, the cell membrane changes composition to become impervious to other spermatozoa. An exception to this is the formation of gestational trophoblastic disease in which multiple sperm enter an ovum; this leads to abnormal zygote formation (Digiulio, Wiedaseck, & Monchek, 2012). Immediately after penetration of the ovum, the chromosomal material of the ovum and spermatozoon fuse to form a zygote. Because the spermatozoon and ovum each carried 23 chromosomes (22 autosomes and 1 sex chromosome), the fertilized ovum has 46 chromosomes. If an X-carrying spermatozoon entered the ovum, the resulting child will have two X chromosomes and will be female (XX). If a Y-carrying spermatozoon fertilized the ovum, the resulting child will have an X and a Y chromosome and will be male (XY).  Fertilization is never a certain occurrence because it depends on at least three separate factors: Equal maturation of both sperm and ovum Ability of the sperm to reach the ovum Ability of the sperm to penetrate the zona pellucida and cell membrane and achieve fertilization Out of this single-cell fertilized ovum (zygote), the future child and also the accessory structures needed for support during intrauterine life (placenta, fetal membranes, amniotic fluid, and umbilical cord) will form. Implantation Once fertilization is complete, a zygote migrates over the next 3 to 4 days toward the body of the uterus, aided by the currents initiated by the muscular contractions of the fallopian tubes. During this time, mitotic cell division, or cleavage, begins. ZYGOTE The zygote is the first cell of the human body formed from the fertilization of sperm and ovum. It containes 46 chromosomes: 44 are autosomes and the remaining are either XX or XY Chromosomes. The zygote journeys from the fallopian tube to the uterus for a period of 3 to 4 days. About 24 hours after fertilization, it undergoes its first cell division. The daughter cells formed from this cell division are called blastomeres. Subsequent cell divisions occur after every 22 hours. When there are already 16 or more blastomeres, the zygote is termed a morula (as it resembles a mulberry mass at this state. It is in the morula form that the zygote travels from the fallopian tube to the uterus. Upon reaching the uterine cavity, the remaining zona pellucida disintegrates and the morula is transformed into a blastocyct.  BLASTOCYST Blastocyst – is a ball like structure composed of an inner cell mass, called embryonic disc or blastocele, occupying one of its poles and an outer layer of rapidly developing cells called trophoblasts or trophoderm. Fluid fills the spaces found within the cells.  The trophoderm layer gives rise to the placenta, fetal membranes, umbilical cord and amniotic fluid. The important functions of the trophoblasts are to: 1. Absorb nutrients from the endometrium 2. Secrete the hormone human chorionic gonadotropin necessary in prolonging the life of corpus luteum.  The blastocoele or embryonic disc gives rise to the 3 primary germ layers which are the: a. Ectoderm – the first germ layer to develop that gives rise to the skin, hair, nails, sense organs, nervous system, mucous membrane of the mouth and anus. b. Endoderm - gives rise to the bladder, lining of the gastrointestinal tract, tonsil, thyroid gland, and respiratory system. c. Mesoderm – The last germ layer to develop that gives rise to the kidney, muskuloskeletal system (bones and muscles), reproductive system and cardiovascular system (heart and blood vessels) Implantation usually occurs high in the uterus, on the posterior surface. If the point of implantation is low in the uterus, the growing placenta may occlude the cervix and make birth of the child difficult (placenta previa), because the placenta can block the birth canal. Almost immediately, the blastocyst burrows deeply into the endometrium and establishes an effective communication network with the blood system of the endometrium. Once implanted, the zygote is called an embryo. Implantation is an important step in pregnancy, because as many as 50% of zygotes never achieve it (Gardosi, 2012). In these instances, the pregnancy ends as early as 8 to 10 days after conception, often before a woman is even aware she was pregnant. Occasionally, a small amount of vaginal spotting appears on the day of implantation because capillaries are ruptured by the implanting trophoblast cells. A woman who normally has a particularly scant menstrual flow could mistake implantation bleeding for her menstrual period. If this happens, the predicted date of birth of her baby (based on the time of her last menstrual period) will be calculated 4 weeks late. The blastocyst is differentiated into three germ layers—the ectoderm, mesoderm, and endoderm. Cells at the periphery are trophoblast cells that mature into the placenta.  TROPHOBLASTS At around the 3rd week of gestation, the trophoblast cells surrounding the blastocyst differentiate in two distinct layers: 1. Cytotrophoblasts: This is the first layer that develops and is also called the Langhan’s layer. It is composed of cells with well differentiated and clear cytoplasm. This layer protects the fetus against treponema pallidum or syphilis but only until the second trimester of pregnancy, the cells of the cytotrophoblasts become less numerous making it an ineffective barrier against syphilis. 2. Syncytiotrophoblast/ syncytium/ plasmotrophoblast The outer layer which originates from the cytotrophoblast is composed of multinucleated cells without cell boundaries. During the second trimester, only a small number of cytotrophoblast cells remain so that it is the syncytium that functions as the primary barrier. However, it is a poor barrier being composed only of a single layer of cells that is capable of blocking completely only a limited number of high molecular weight substances such as insulin and HCG.  1. Intervillus Spaces: these are spaces (lacunae) that appear in the syncytium, increase in size and fuse together to form the “chorio- decidual space” or “intervillus space” Erosion of the decidual blood vessels by the enzymatic action of the trophoblasts allows blood to circulate in this space.  2. Villi: The outer syncytium and inner Langhan’s cells form buds surrounding the developing ovum called the primary villi. When the mesoderm invades the center of the primary villi they are called the secondary villi. When blood vessels (branches from the umbilical vessels) develop inside the mesodermal core, they are called tertiary villi. CHORIONIC VILLI As early as 12 days after fertilization tiny projections around the zygote, called villi, can be seen. These villi are classified as: Chorion Frondosum: These are the chorionic villi in contact with decidua basalis that proliferate rapidly because they receive rich blood supply from the uterus. They will later form the fetal side of the placenta. These villi are responsible for absorbing nutrients and oxygen from maternal blood stream and disposing of fetal waste products including carbon dioxide. Chorion Laeve: These are the chorionic villi not involved with implantation that gradually degenerates, becoming very thin, and eventually forming the chorionic membrane. These villi are also referred to as the bald chorion. The chorion laeve is composed of cytotrophoblasts and fetal mesodermal cells. DECIDUA: The Endometrium of Pregnancy After implantation, the endometrium is referred to as the decidua, the specialized endometrium of pregnancy. The functions of the decidua are: 1. The decidua is the most ideal site for implantation because of its rich blood supply that ensures optimum placental growth and development. 2. It provides easy access to the birth of the baby at the end of gestation as it is continuous with the birth canal. 3. It may prevent infections coming from the vagina and cervix. 4. It produces the following hormones: prolactin, relaxin, corticotropin releasing hormone (CRH), growth hormones, prostaglandin, oxytocin and endothelin-1.  It is composed of 3 layers: 1. Decidua parietalis – located under decidua basalis. 2. Decidua Basalis – The layer where implantation takes place, it will later form the maternal side of the placenta. 3. Decidua Capsularis – The layer which enclose the blastocyst after implantation. At about the 4th month of gestation, when the gestational ring grows large enough to occupy the entire uterine cavity, the space between the decidua vera and decidua capsularis is obliterated and the two deciduas fuses together. They will then, referred to as the decidua vera.  The decidua parietalis and basalis are composed of 3 layers: 1. Zona compacta located at the surface where the neck of the glands are found and composed of closely packed stroma cells. 2. Zona spongiosa consists of blood vessels and tortuous glands rich in secretions. The separation of the placenta occurs at this layer. The functional layer is the zona spongiosa and compacta. 3. Zona basalis – which remains after delivery to give rise to the new endometrium after delivery. FETAL MEMBRANES The fetal membranes enclose the fetus and the amniotic fluid, and protect the fetus against ascending bacterial infection as long as it is not ruptured.  It is composed of 2 membranes: 1. Chorionic membrane – originates from the portion of the chorionic villi not involve with implantation, the chorion leave. - it is thick, opaque and friable. - it is in contact with the decidua and is attached at the margins of the placenta - it functions to provide support to the amniotic membrane. 2. Amniotic Membrane – is a smooth, thin, tough, and translucent membrane directly enclosing the fetus and the amniotic fluid. - it is continuous with the umbilical cord and covers the fetal surface of the placenta and is also the outer covering of the umbilical cord. - contains cells that produce the amniotic fluid. The amnion and the chorion does not have nerve supply and blood vessels so that the mother neither the fetus experience pain when they rupture. The chorionic membrane and the amniotic membrane lie adjacent to the entire surface of the decidua parietalis. AMNIOTIC FLUID The amniotic fluid is the medium in which the fetus and the cord float inside the amniotic membrane. It is not in a static state but is in continuous turn over; 350 – 500 ml of it is produced and replaced each hour. Daily exchange of amniotic fluid at 6 months is around 6 gallons.  Production and removal of amniotic is achieved through the following mechanisms: 1. The fetus contributes to the amniotic fluid by: - active secretion from the epithelium of the amniotic membrane - transudation from the fetal circulation - fetal urination. Fetal urine is the primary source of amniotic fluid late in pregnancy. 2. The mother contributes to the amniotic fluid by transudation from maternal circulation. Maternal serum composes most of the fluid early in pregnancy.  3. Removal or uptake of amniotic fluid is by: - absorption through the amnion to the maternal circulation - By fetal swallowing, this is the chief mechanism which controls the volume of the fluid. Volume: 1. The volume of amniotic fluid increases from the first trimester until the 38th week. Then, it diminishes slightly until term. 2. Normally, amniotic fluid volume ranges from 500-1200ml, averaging at 1000ml.  Composition: 1. It is composed of 99% water and 1% solid particles. 2. It contains albumin, urea, uric acid, creatinine, lecithin, sphingomyelin, bilirubin, minerals, and suspended materials such as desquamated epithelial cells and vernix caseosa. Color 1. It is clear and colorless to straw colored. 2. Green tinged or meconium stained amniotic fluid in non breech presentation signified fetal distress.  3. Golden colored amniotic fluid signifies hemolytic disease such as RH or ABO incompatibility. 4. Gray colored amniotic fluid indicates infection. 5. Bloody amniotic fluid at the time of rupture indicates vasa previa. 6. Brownish, coffee or tea-colored amniotic fluid indicates fetal death. pH: 7.0 to 7.25, reaction is neutral to alkaline Specific Gravity: -1.005 to 1.025  Functions of Amniotic Fluid 1. Protection: - of the fetus from trauma, blows and pressure - of the fetus from uterine contractions - of the fetus from sudden changes in temperature - of the cord from pressure - of the fetus from infection 2. Promotes symmetrical musculoskeletal development by allowing freedom of movement. 3. Acts as an excretion and secretion system.  4. Source of oral fluid for the fetus who swallows it. 5. Aids in diagnosis of maternal and fetal complications through amniocentesis 6. Assists in labor by: - intact membranes ids in the effacement and dilatation of the cervix. - once it ruptures, the fluid washes the birth canal and serves as an antiseptic. - it acts as a lubricant making the birth canal more slippery for the passage of the fetus.  UMBILICAL CORD Function: - The umbilical cord or funis is the structure that connects the fetus to the placenta. - Its main function s to carry oxygen and nutrients from the placenta to the fetus and return unoxygenated blood and fetal waste products to the placenta.  BLOOD VESSELS: 1. it is composed of 2 arteries which carry the most unoxygenated blood to the placenta and, one vein (the left vein as the right vein disappeared in early fetal life) which carries the most oxygenated blood to the fetus. 2. In about 1% of singleton pregnancies, the umbilical cord contain only 2 vessels, this condition is often associated with renal anomalies. This increase by 6 to 7% in multiple pregnancies.  Length: - It is about 50 to 55cm long and 2 cm in diameter. It appears dull white, moist and covered by amnion. 1. Short cord which may lead to: - intrapartum hemorrhage due to premature separation of the placenta. - delayed descent of the fetus during labor - inversion of the uterus 2. Long cord may lead to: - cord presentation and cord prolapse - coiling of the cord around the neck - true knots of the cord.  Origin: 1. The umbilical cord originated from the yolk sac and umbilical vesicles. 2. Early in fetal like the umbilical vesicle and the intestines are connected to each other. Later, the intraabdominal portion of the umbilical vesicles which extends from the umbilicus to the intestines atrophy and disappear. Sometimes it remain patent, a condition called Meckel diverticulum. Wharton’s Jelly: It is the gelatinous substance found inside the cord.  Cord Insertion: 1. Central Insertion – normally, the cord is inserted at the center of the fetal surface of the placenta. 2. Lateral insertion – when the cord is inserted away from the center of the placenta but not at its edges. 3. Velamentous insertion – when the chorioamniotic membrane that surrounds the cord is inserted in the membranes about 5 to 10 cm away from the edge of the placenta and not on placental mass. 4. Battledore insertion – when the cord is inserted at the edge of the placenta.  Cord Abnormalities: 1. Vasa Previa – can occur when the vessels connecting a succenturiate lobe with the main placenta pass at the region of the internal os. Cause: - no known cause - believed to be due to trophotropism. Signs and symptoms: - the classic sign of vasa previa is a sudden gush of bright red blood at the time of the rupture of membranes. - blood loss results in sudden fetal bradycardia. Diagnosis: - can be detected during the pregnancy as early as 16 weeks gestation with the use of a transvaginal sonography. - if the diagnosis detects a vasa previa, a cesarian section is the safe method of delivery.  2. Knots of the cord – may be caused by fetal movements and may lead to perinatal loss. - its incidence is high in monoamniotic twinning. True knot – when the fetus passes through a loop of the cord. If pulled tight, fetal asphyxia may occur. False knot – localized collection of Wharton’s jelly containing a loop of umbilical vessels. 3. Loops of the cord – the cord may coil around the fetal body and neck. -When cord coil is in the neck it is called nuchal cord. 4. Torsion of the cord – Caused by deficiency of Wharton’s jelly. Infants seen with cord torsion are mostly stillborn. Normal umbilical cord 6. Cord Cysts – True cord cyst are small and derived from the remnants of the umbilical vesicle and allantois. False cysts are large and derived from Wharton’s jelly. 7. Edema of the cord is associated with edema of the fetus which is common in dead macerated fetus. 8. Single umbilical artery – may be associated with other fetal congenital anomalies. PLACENTA Origin: The placenta is formed from the chorionic villi and decidua basalis. Weight: 1. Placenta is a discoid organ weighing approximately 500 grams at term, with a diameter of 15 to 20cm and about 3cm thick. 2. It occupies about ¼ of the uterine cavity. Its estimated total surface area at term is 10m2. Uteroplacental blood flow at term is 700 to 900ml.  Maternal and Fetal Sides 1. Maternal Side: It faces the mother, composed of 15 to 20 cotyledons. Each cotyledon is supplied with one artery and one vein. 2. Fetal Side – it faces the fetus. The amnion that covers it gives it a white and shiny appearance.  Placental Barrier: Maternal and fetal blood do not mix although the oxygen and nutrient supply from the fetus comes from the mother. Fetal and maternal circulation is separated by cytothrophoblast, syncytium, and walls of fetal blood vessels. Passage of Substances Across the Placenta. The exchange of substances between the mother and the fetus is regulated by the following processes: 1. Diffusion: Carbon dioxide, oxygen, fetal waste products, sodium, chloride and fat soluble vitamins. 2. Facilitated diffusion: Glucose  3. Active Transport: Amino acids, water soluble vitamins, iron, calcium and iodine. 4. Pinocytosis: At the end of pregnancy antibodies such as IgG that provides natural passive immunity during the first three months after birth cross the placenta. Only those antibodies which the mothers possess will be transferred to the fetus. 5. Defects in the Placenta: Breaks in the placental membrane allows passage of some substances between mother and fetus. *Pregnant women and neonates are particularly vulnerable to infectious disease due to altered and underdeveloped immune responses. Vaccination in pregnancy provides maternal protection through active immunization, while passive maternal antibody transfer across the placenta to the developing fetus has the potential to protect neonates and infants.  FUNCTIONS OF THE PLACENTA 2 MAIN IMPORTANT FUNCTION: 1. It serves as a transfer organ for metabolic products. 2. It produces or metabolizes the hormones and enzymes necessary in the maintenance of pregnancy. The nourishment of the placenta comes from the maternal blood and it can grow only up to a limited time, after which, it begins to degenerate with functional capacity and oxygen consumption diminishing. This happens after 40-42 weeks of gestation, in which proper nutritional supply from the maternal blood, the placenta begins to shrink and function less effectively. This is the reason why it is dangerous for the fetus to remain in utero after 42 weeks of gestation.  FUNCTIONS OF THE PLACENTA 1. Respiratory system – exchange of gases takes place through the process of diffusion and not in fetal lungs. Oxygen and Carbon dioxide pass across the placenta by simple diffusion. The fetal hemoglobin has more affinity and oxygen carrying capacity than adult hemoglobin. 2. Renal System – Waste products of the fetus are excreted through the placenta and detoxified in the mother’s liver. Waste products of the fetus such as urea are passed to maternal blood by simple diffusion through the placenta.  3. Gastrointestinal System - Nutrients pass from the placenta to the fetus via active transport and diffusion. The food eaten by the mother is already broken down in its simplest form by the time it reaches the placenta. The placenta selects the nutrients needed by the fetus, sometimes even depleting maternal stores as in the case of glucose and iron. 4. Circulatory System – Feto-placental circulation is functional 17 days after fertilization. Maternal blood flow through the placenta at term is about 500ml/min  5. Production of enzymes – Enzymes produced by the placenta include oxytocinase, monoamino oxidase, insulinase, histaminase and heat stable alkaline phosphatase. 6. Endocrine system - the placenta produces the following hormones: A. Protein Hormones: a. Human Chorionic Gonadotropin (HCG) – it is a glycoprotein produced by the syncytiotrophoblast. It is secreted directly into the maternal blood, but is not absorbed by the placenta so that virtually none of it reaches the fetal circulation. - rises sharply after implantation, reaching a peak of 100,000 mIU/ml about the 60th day (8th to 10th week) of pregnancy then falls sharply by the 100-120 day to a level of 30,000 mIU/ml and is maintained at this level until term. It disappears from the circulation at approximately 50% per week.  Functions of HCG: Luteutrophic – stimulates the corpus luteum in the first 10 weeks of pregnancy to produce estrogen and progesterone until the syncytiotrophoblast are mature enough to produce progesterone. Believed by some scientists to have an immunologic role called “lymphocyte response” which inhibits the mother from producing antibodies against the foreign placenta. Stimulates testosterone production in male fetus in order to cause development of the penis and other male organs. Pregnancy Test  HCG Molecule is composed of 2 subunits: 1. alpha subnit which is similar to that of FSH, LH and TSH. 2. beta subunit which is specific to hCG and which is the one tested in pregnancy test Estimation of beta-hCG is used for: a. diagnosis of pregnancy b. diagnosis of ectopic pregnancy c. diagnosis and follow-up of trophoblastic disease.  b. Human Placental Lactogen (HPL) – It is a polypetide hormone produced by the syncytiotrophoblast - can be detected y the 5 -6 week of pregnancy, rises th th steadily until the 36th week to be 6mg/l (6-7ug/ml).It is the hormone produced in largest amount during pregnancy. Its level is proportional to the placental mass. - it is immunologically and physiologically similar to the Pituitary Growth Hormone (hGH) Supposed action of HPL: a. Increasing free fatty acids to provide a ready source of energy for mother and fetal nutrition. b. Reduces activity of insulin to spare both glucose and protein from being totally utilized y maternal tissues. This explains the anti-insulin effect of hPL. c. Growth promotion of the fetus due to increased supply of fatty acids, glucose and amino acids. d. Promotes development of maternal breast tissues in preparation for breastfeeding after delivery. Responsible for production of colostrum.  c. Human Chorionic thyrotrophin (hCT) – no significant role has been established for it, but it is probably responsible for increased maternal thyroid activity and promotion of fetal thyroid development. d. Hypothalamic pituitary like hormones – include the gonadotropin releasing hormone (GnRH), coticotropin releasing factor (CRF), ACTH and melanocyte stimulating hormone. e. Other hormones such as inhibin, relaxin and beta endorphins.  B. Steroid Hormones a. Estrogen - Estrogen (primarily estriol) is produced as a second product of the syncytial cells of the placenta. Estrogen contributes to the woman’s mammary gland development in preparation for lactation and stimulates uterine growth to accommodate the developing fetus. - is often referred to as the “hormone of women,” b. Progesterone - progesterone as the “hormone of mothers.” This is because, although estrogen influences a female appearance, progesterone is necessary to maintain the endometrial lining of the uterus during pregnancy. It is present in maternal serum as early as the fourth week of pregnancy as a result of the continuation of the corpus luteum. After placental production begins (at about the 12th week), the level of progesterone rises progressively during the remainder of the pregnancy. This hormone also appears to reduce the contractility of the uterus during pregnancy, thus preventing premature labor. Placental circulation As early as the 12th day of pregnancy, maternal blood begins to collect in the intervillous spaces of the uterine endometrium surrounding the chorionic villi. By the third week, oxygen and other nutrients such as glucose, amino acids, fatty acids, minerals, vitamins, and water osmose from the maternal blood through the cell layers of the chorionic villi into the villi capillaries. From there, nutrients are transported to the developing embryo. Because placental transfer is so effective, all but a few substances are able to cross from the mother into the fetus. Because almost all drugs are able to cross into the fetal circulation, it is important that a woman take no nonessential drugs (including alcohol and nicotine) during pregnancy (Cleary, Eogan, O’Connell, et al., 2012). Alcohol, as an example, because it perfuses across the placenta so well, can cause fetal alcohol spectrum disorder (e.g., unusual facial features, lowset ears, and cognitive challenge). As it’s difficult to tell what quantity is “safe,” pregnant women are advised to drink no alcohol during pregnancy to avoid these disorders (Rogers & Worley, 2012). Theoretically, because the exchange process depends on osmosis, there is no direct exchange of blood cells between the embryo and the mother during pregnancy. Occasionally, however, fetal cells do cross into the maternal bloodstream, as well as fetal enzymes such as alpha-fetoprotein (AFP) produced by the fetal liver (this allows testing of fetal cells for genetic analysis as well as the level of AFP in the maternal blood). As the number of chorionic villi increases with pregnancy, the villi form an increasingly complex communication network with the maternal bloodstream. Intervillous spaces grow larger and larger, becoming separated by 30 or more partitions or septa. These compartments (cotyledons) are what make the maternal side of the placenta look rough and uneven. Osmosis – a process by which molecules of a solvent tend to pass through a semipermeable To provide enough blood for exchange, the rate of uteroplacental blood flow in pregnancy increases from about 50 ml/min at 10 weeks to 500 to 600 ml/min at term. No additional maternal arteries appear after the first 3 months of pregnancy; instead, to accommodate the increased blood flow, the arteries increase in size. The woman’s heart rate, total cardiac output, and blood volume all increase to supply blood to the placenta (Pipkin, 2012). Braxton Hicks contractions, the barely noticeable uterine contractions present from about the 12th week of pregnancy on, aid in maintaining pressure in the intervillous spaces by closing off the uterine veins momentarily with each contraction. Uterine perfusion and placental circulation are most efficient when the mother lies on her left side, as this position lifts the uterus away from the inferior vena cava, preventing blood from becoming trapped in the woman’s lower extremities. If the woman lies on her back and the weight of the uterus compresses on the vena cava, placental circulation can be so sharply reduced that supine hypotension (i.e., very low maternal blood pressure and poor uterine circulation) can occur (Coad & Dunstall, 2011a). At term, the placental circulatory network has grown so extensively that a placenta weighs 400 to 600 g (1 lb), onesixth the weight of the newborn. If a placenta is smaller than this, it suggests circulation to the fetus may have been inadequate. A placenta bigger than this also may indicate circulation to the fetus was threatened, because it suggests the placenta was forced to spread out in an unusual manner to maintain a sufficient blood supply. The fetus of a woman with diabetes may also develop a larger than usual placenta from excess fluid collected between cells. ABNORMALITIES OF THE PLACENTA PLACENTA BIPARTITA 1. Multiple Placentas: Are of different kinds: Placenta Bipartita – placenta is not completely divided into 2 lobes. Placenta Duplex – placenta is separated completely into parts. 2. Succenturiate Placenta - placenta having an accessory lobe with blood vessels connected to it. 3. Ring-shaped placenta – associated with fetal growth retardation, postpartum and antepartum bleeding. 4. Fenestrated Placenta – in most cases of this type of placental abnormality, the central portion of the maternal side of the placenta is missing. 5. Extrachorial Placenta- the chorionic plate of the placenta is smaller than the basal plate. Are of two types: a. Circumvallate Placenta – when such fetal surface presents a central depression surrounded by a thickened white- grayish ring which is a double layer of amnion and chorion with degenerated decidua and fibrin between the two layers. b. Circummarginate placenta – When the white grayish ring is located at the margin of the placenta. 6. Membranaceous Placenta – Fetal Membranes at the surface of the placenta are covered by functioning villi. Also known as placenta diffusa. 7. Large Placenta – usually encountered in syphilis and erythroblastosis fetalis. 8. Placental Polyp – are retained placentas that become polyps consisting of villi in varying stages of degeneration and may be covered by regenerated endometrium. 9. Abnormally Adherent Placenta Placenta Accreta – the chorionic villi penetrate deeply and firmly attached in the decidua basalis or the myometrium. Placenta Accreta is strongly associated with placenta previa.  Placenta Increta – when the villi penetrate and invade deeply into the myometrium. Placenta Percreta – Placenta percreta occurs when the placental villi penetrate through the myometrium to the peritoneum covering the uterus, sometimes being attached to the other organs surrounding the uterus such as the bladder. 10. Placental Infection – (Placentitis, Chorioamnionitis): Infection of the placenta, caused by virus or bacteria, is common after prolonged rupture of membranes. The area most commonly affected is the amnion and chorion near the cord insertion. Signs & symptoms: Mother complains of chills, uterine tenderness, hypertonicity of the uterus and malodorous amniotic fluid. Laboratory Findings: leukocytosis (shift to the left), increased sedimentation rate, heavy colonization of pathogens in cervical and uterine culture. Milky or steamy membranes due to presence of leukocytes and exudates.  Management: Evacuation of uterus: induced abortion or labor depending on the stage of gestation. Parenteral antibiotics Oxytocics Symptomatic treatment: paracetamol, analgesics, increased fluids, semi- fowlers position. 11. Placental Insufficiency – refers to reduced placenta function that can result in untoward fetal outcome. - a placenta that suffers from PI may be smaller than usual and may show signs of premature aging. - the most common effect is restricted fetal growth and development resulting in the birth of a SGA infant. - SGA neonate has reduced weight, altered body proportions (large head, small thin body), altered distribution of organ weights. - SGA is also at risk for congenital anomaly, hypoxia, acidosis, hypothermia. Hypoglycemia, polycythemia and meconium aspiration. Long term effects includes seizures, cerebral palsy, reduced IQ, learning and behavioral disorders  Causes of Placental Insufficiency: Abnormal placental anatomy resulting in diminished placental function such as placenta previa and circumvallate placenta. Decreased placental perfusion such as what happens in cigarette smoking, infarction, partial separation and premature placental aging. Maternal disorders which reduces placental blood supply or perfusion such as severe maternal anemia, DM, preeclampsia, renal disease and heart disease. Excessive demands such as what happens in multiple pregnancy  Types: Acute PI occurs suddenly such as what happens after premature separation of the placenta resulting in fetal distress. Chronic PI has been occurring over time in which there is prolonged suboptimal nutritional or gaseous exchange between the mother and the placenta.