Nursing Care During Normal Pregnancy and Care of the Developing Fetus

Stages of Fetal Development

• In approximately 38 weeks, a fertilized egg matures into a fully developed fetus, ready for birth.

Fertilization and Implantation

• Fertilization: The union of an ovum and a spermatozoon.
  • Ovum is capable of fertilization for 24 hrs (48 hrs at most).
  • Spermatozoon's functional life is about 48 hrs (72 hrs at most).
• Implantation: The contact between the growing structure (blastocyst) and the endometrium.
  • Blastocyst attaches to the endometrium.
  • Trophoblast cells form the placenta and membranes.

Terms Describing Fetal Growth

• Ovum: From ovulation to fertilization.
• Zygote: From fertilization to implantation.
• Embryo: From implantation to 5-8 weeks.
• Fetus: From 5-8 weeks until term.
• Conceptus: Developing embryo and placental structures throughout pregnancy.
• Age of Viability: Generally accepted as 24 weeks or when the fetus weighs more than 500-600 grams.

Decidua

• Specialized endometrium of pregnancy.
  • Decidua Basalis: Lies directly under the embryo.
  • Decidua Capsularis: Encapsulates the surface of the trophoblast.
  • Decidua Vera: The remaining portion of the uterine lining.

Placenta Functions

• Serves as fetal lungs, kidneys, gastrointestinal tract, and endocrine organ.

Endocrine Functions of Placenta

• Produces hormones:
  • Human Chorionic Gonadotropin (HCG):
    • First hormone produced.
    • Present in maternal blood and urine as early as the 1st missed menstrual period.
    • Basis of pregnancy tests.
  • Estrogen:
    • "Hormone of women".
    • For breast development and uterine growth.
  • Progesterone:
    • "Hormone of mothers".
    • Maintains the endometrial lining.
  • Human Placental Lactogen (HPL):
    • Promotes breast growth.
    • Regulates maternal glucose, protein, and fat levels.

Umbilical Cord

• Transports oxygen and nutrients to the fetus and returns waste products to the placenta.
• Contains one vein and two arteries.

Origin and Development of Organ Systems

• Zygote cells are totipotent stem cells for the first 4 days, having the potential to grow into any cell in the human body.
• Embryo cells begin to show differentiation in the next 4 days, becoming pluripotent stem cells that have lost some ability to become any body cell.
• Cells grow more specific and become multipotent.
• Development proceeds in a cephalocaudal (head to tail) direction.

Primary Germ Layers:

• Ectoderm:
  • Covers the outside of the embryo.
  • Develops into the central nervous system (brain, spinal cord), peripheral nervous system, skin, hair, nails, sense organs, and mammary glands.
• Mesoderm:
  • Found between the ectoderm and endoderm.
  • Develops into the upper urinary system (kidneys, ureters), heart, reproductive system, and circulatory system.
• Endoderm:
  • The innermost layer of cells or tissues of an embryo in early development.
  • Develops into the lower urinary system (bladder, urethra), lining of the gastrointestinal tract, and respiratory tract.
• All organ systems are complete at 8 weeks gestation (end of the embryonic period).
  • During organogenesis (organ formation), the growing structure is most vulnerable to teratogens.
  • Teratogens: Any factor that affects the fertilized ovum, embryo, or fetus (e.g., teratogenic medicines, infection, cigarette smoking, or alcohol ingestion).

Cardiovascular System

• One of the first systems to become functional in intrauterine life.
• The septum that divides the heart into chambers develops during the sixth or seventh week.
• Heart valves develop in the seventh week.
• Heartbeat may be heard with a Doppler instrument as early as the 10th to 12th week of pregnancy.
• The heart rate of a fetus is affected by oxygen level, activity, and circulating blood volume, similar to adulthood.
• After the 28th week of pregnancy, when the sympathetic nervous system matures, the heart rate stabilizes to 110-160 beats/minute.

Fetal Circulation

• Blood arriving at the fetus from the placenta is highly oxygenated.
• This blood enters the fetus through the umbilical vein.
• The relatively less-well-oxygenated blood entering the right atrium from the superior vena cava preferentially flows across the tricuspid valve into the right ventricle.
• A small portion flows to the lungs via the pulmonary arteries; the bulk goes into the descending aorta via the ductus arteriosus.
• Blood flow in the descending aorta supplies the abdominal organs and lower extremities and returns blood to the placenta via the umbilical arteries, completing the circuit.
• The ductus venosus shunts oxygenated blood from the placenta away from the semifunctional liver and toward the heart.
• The foramen ovale allows oxygenated blood in the right atrium to reach the left atrium.

Fetal Hemoglobin

• Differs from adult hemoglobin; it is more concentrated.
• Newborn hemoglobin: $17.1g/100ml$
• Adult hemoglobin: $11g/100ml$
• Newborn hematocrit: $53$
• Adult hematocrit: $45$

Respiratory System

• Digestive and respiratory tubes exist as one at the first week of intrauterine life.
• By the end of the fourth week, a septum begins to divide the esophagus from the trachea.
• At the same time, lung buds appear on the trachea.
• Spontaneous respiratory practice movements begin as early as 3 months gestation and continue throughout pregnancy.
• Lung fluid with a low surface tension and low viscosity forms in alveoli to aid in the expansion of the alveoli at birth.
• Surfactant, a phospholipid substance, is formed and excreted by the alveolar cells of the lungs.
• This substance decreases alveolar surface tension on expiration, preventing alveolar collapse and improving the infant’s ability to maintain respirations in the outside environment at birth.

Two components of surfactant:

• Lecithin
• Sphingomyelin
  • Early in the formation of surfactant, sphingomyelin is the chief component.
  • At 35 weeks, there is a surge production of lecithin that becomes the chief component.
  • As the fetus practices breathing movements, surfactant mixes with amniotic fluid.
  • Amniocentesis: Analysis of the lecithin/sphingomyelin (L/S) ratio in surfactant is the primary test of fetal maturity.

Nervous System

• A neural plate (a thickened portion of the ectoderm) is apparent by the third week of gestation.
• The top portion differentiates into the neural tube, which will form the central nervous system (brain and spinal cord), and the neural crest, which will develop into the peripheral nervous system.
• All parts of the brain (cerebrum, cerebellum, pons, and medulla oblongata) form in utero, although none are completely mature at birth.
• Brain growth continues at high levels until 5 or 6 years of age.
• Brain waves can be detected on EEG by the eighth week.
• The eye and the inner ear develop as projections of the original neural tube.
• By 24 weeks, the ear is capable of responding to sound, and the eyes exhibit a pupillary reaction, indicating sight is present.
• This system seems prone to insult during the early weeks of the embryonic period and can result in neural tube disorders such as meningocele, especially if there is a lack of folic acid.
• Sources of folic acid: green leafy vegetables and vitamins.

Endocrine System

• The fetal pancreas produces insulin needed by the fetus.
• Insulin is one of the few substances that does not cross the placenta from the mother to the fetus.
• The thyroid and parathyroid glands play vital roles in fetal metabolic function and calcium balance.
• The fetal adrenal glands supply a precursor necessary for estrogen synthesis by the placenta.

Digestive System

• The tract canalizes (hollows out) to become patent.
• Later in the pregnancy, the endothelial cells of the GIT proliferate extensively, occluding lumen once more, and the tract must canalize again.
• Atresia (blockage) or stenosis (narrowing) of the track are common fetal anomalies and develop if either the first or second canalization does not occur.
• By the sixth week of intrauterine life, the intestine becomes too large to be contained by the abdomen.
• A portion of the intestine is pushed into the base of the umbilical cord where it remains at about 10 weeks of intrauterine life, or until the abdominal cavity has grown enough to accommodate the bulky intestines.
• As the intestine returns to the abdominal cavity, it must rotate 180 degrees.
• Failure to do so can result in inadequate mesentery attachments that can lead to volvulus of the intestine in the newborn.
• If any intestines remain outside the abdomen in the base of the cord, a congenital anomaly, omphalocele, will be present at birth.
• Gastroschisis: When the original midline fusion that occurred at the early cell stage is incomplete.
• Meconium: A collection of cellular wastes, bile, fats, mucoproteins, mucopolysaccharides, and portions of the vernix caseosa accumulates in the intestines as early as the 16th week.
• It is sticky in consistency and appears black or dark green (obtaining its color from bile pigment).
• Nursing Responsibility: Record that a newborn has passed meconium as this rules out stricture of the anus.

Musculoskeletal System

• During the first 2 weeks of fetal life, cartilage prototypes provide position and support of the fetus.
• Ossification begins at about the 12th week and continues all through fetal life and into adulthood.
• Carpals, tarsals, and sternal bones generally do not ossify until birth is imminent.
• A fetus can be seen to move on UTZ as early as the 11th week, although the mother does not feel this movement (quickening) until 16 to 20 weeks of gestation.

Reproductive System

• A child's sex is determined at the moment of conception by a spermatozoon carrying an X or Y chromosome and can be ascertained as early as 8 weeks by chromosomal analysis or analysis of fetal cells in the mother’s bloodstream.
• The testes form in the abdominal cavity and do not descend into the scrotal sac until the 34th to 38th week of intrauterine life.
• Because of this, many male preterm infants are born with undescended testes.
• Testes that do not descend (cryptorchidism) require surgery as they are associated with poor sperm production and possibly testicular cancer later in life.

Urinary System

• The presence of kidneys is not essential for life before birth because the placenta clears the fetus of waste products.
• Urine is formed by the 12th week and is excreted into the amniotic fluid by the 16th week of gestation.
• At term, fetal urine is being excreted at a rate of up to $500ml/day$.

Integumentary System

• Fetal skin appears thin and almost translucent until subcutaneous fat begins to be deposited underneath it at about 36 weeks.
• Lanugo: The fine downy hair that covers the fetal skin, serves as insulation to preserve warmth in utero, as well as a cream cheese-like substance (vernix caseosa), which is important for lubrication and for keeping the skin from macerating in utero. Both are present at birth.

Immune System

• Immunoglobulin (Ig) G maternal antibodies cross the placenta into the fetus as early as the 20th week and 24th week of intrauterine life to give a fetus temporary passive immunity against diseases for which the mother has antibodies.
• These include: poliomyelitis, rubella (German Measles), rubeola (regular measles), diphtheria, tetanus, infectious parotitis (mumps), hepatitis B, and pertussis (whooping cough).

Milestones of Fetal Growth and Development

• Both ovulation and gestational age are reported in lunar months (4-week periods) or in trimesters (3-month period).
• In lunar months, a total pregnancy is 10 months (40 weeks or 280 days) long.
• A fetus grows in utero for 9.5 lunar months or three full trimesters (38 weeks or 266 days).

End of Fourth Gestational Week

• The length of the embryo is about $0.75 cm$, weight is about $400 mg$.
• The spinal cord is formed and fused at the midpoint.
• The head is large in proportion and represents about one-third of the entire structure
• The rudimentary heart appears as a prominent bulge on the anterior surface.
• Arms and legs are bud-like structures; rudimentary eyes, ears, and nose are discernible.

End of Eighth Gestational Week

• The length of the fetus is about $2.5 cm$ (1 in.); weight is about $20 g$.
• Organogenesis is complete.
• The heart, with a septum and valves, beats rhythmically.
• Facial features are definitely discernible; arms and legs have developed.
• External genitalia are forming, but sex is not yet distinguishable by simple observation.
• The abdomen bulges forward because the fetal intestine is growing so rapidly.
• A sonogram shows a gestational sac, which is diagnostic of pregnancy.

End of 12th Gestational Week

• The length of the fetus is 7 to $8 cm$, weight is $45g$.
• Nail beds are forming on fingers and toes.
• Spontaneous movements are possible, although they are usually too faint to be felt by the mother.
• Some reflexes, such as the Babinski reflex, are present.
• Bone ossification centers begin to form.
• Tooth buds are present.
• Sex is distinguishable on outward appearance.

End of 16th Gestational Week

• The length of the fetus is 10-17 cm.
• Weight is 55 to $120g$.
• Fetal heart sounds are audible by an ordinary stethoscope.
• Lanugo is well-formed.
• Both the liver and pancreas are functioning.
• The fetus actively swallows amniotic fluids, demonstrating an intact but uncoordinated swallowing reflex; urine is present in amniotic fluid.
• Sex can be determined by ultrasonography.

End of 20th Gestational Week

• Fetal length: $25cm$, weight: $223g$.
• Spontaneous fetal movements can be sensed by the mother (quickening).
• Antibody production is possible.
• Hair, including eyebrows, forms on the head; vernix caseosa begins to cover the skin.
• Meconium is present in the upper intestine.
• Brown fat, a special fat that aids in temperature regulations, begins to form behind the kidneys, sternum, and posterior neck.
• Passive antibody transfer from mother to fetus begins.
• Definite sleeping and activity patterns are distinguishable as the fetus develops biorhythms that will guide sleep/wake patterns throughout life.

End of 24th Gestational Week (Second Trimester)

• Fetal length: 28 to $36cm$, weight: $550g$.
• Meconium is present as far as the rectum.
• Active production of lung surfactant begins.
• Eyelids, previously fused since the 12th week, now open; pupils react to light.
• Hearing can be demonstrated by response to sudden sound.
• When fetuses reach 24 weeks, or 500 to $600g$, they have achieved a practical low-end age of viability if they are cared for after birth in a modern intensive care nursery.

End of 28th Week

• Fetal length: 35-38 cm; weight: $1,200 g$.
• Lung alveoli are almost mature; surfactant can be demonstrated in amniotic fluid.
• Testes begin to descend into the scrotal sac from the lower abdominal cavity.
• The blood vessels of the retina are formed but thin and extremely susceptible to damage from high oxygen concentrations (an important consideration when caring for preterm infants who need oxygen).

End of 32nd Gestational Week

• Fetal length: 38-43cm; weight: $1,600g$.
• Subcutaneous fat begins to be deposited (the former stringy, “little old man” appearance is lost).
• Fetus responds by movement to sounds outside the mother’s body.
• An active Moro reflex is present.
• Iron stores, which provide iron for the time during which the neonate will ingest only breast milk after birth, are beginning to be built.
• Fingernails reach the end of fingertips.

End of 36th Gestational Week

• Fetal length: 42-48cm;weight: 1,800 – $2,700g$ (5-6lb).
• Body stores of glycogen, iron, carbohydrate, and calcium are deposited.
• Additional amounts of subcutaneous fat are deposited.
• Sole of the foot has only one or two crisscross creases compared with a full crisscross pattern evident at term.
• Amount of lanugo begins to diminish.
• Most fetuses turn into a vertex (head down) presentation during this month.

End of 40th Gestational Week

• Fetal length: 48-52 cm (crown to rump, 35 to 37 cm); weight: $3,000g$ (7-7.5lb).
• Fetus kicks actively, sometimes hard enough to cause the mother considerable discomfort.
• Fetal hemoglobin begins its conversion to adult hemoglobin.
• Vernix caseosa starts to decrease after the infant reaches 37 weeks gestation.
• Fingernails extend over the fingertips.
• Creases on the soles of the feet cover at least two-thirds of the surface.

Assessment of Fetal Growth and Development

• Tests for fetal growth and development are commonly done for a variety of reasons:
  • Predict the outcome of the pregnancy
  • Manage the remaining weeks of the pregnancy
  • Plan the possible complication at birth.
  • Plan for problems that may occur in the newborn infants.
  • Decide whether to continue the pregnancy.
  • Find conditions that may affect future pregnancies.
• Nursing responsibilities:
  • Assessment and verifying before the procedure
  • Secure informed consent
  • Explain the procedure to patient and relatives
  • Providing follow-up care

Assessing Fetal Growth and Health

• Health History
• Physical Examination
• Fetal Growth (McDonald's rule)
• Fetal heart rate
• Daily fetal movement count (kick count)
• Rhythm strip testing
• Nonstress testing
• Vibroacoustic stimulation
• Ultrasonography
• Biophysical profile
• Magnetic resonance imaging
• Maternal serum

Invasive Fetal Testing:

• Chronic villi sampling
• Amniocentesis
• Percutaneous umbilical blood sampling
• Fetoscopy