MCHN-fertilization

Fertilization

The fusion of the sperm cell nucleus with the egg cell nucleus to produce a zygote (fertilized egg).

Assessment of Fetal Growth and Development

A process to predict the outcome of pregnancy, manage remaining weeks, plan for complications at birth, and find conditions affecting future pregnancies.

Health History

Assessment of the mother including pre-pregnancy illnesses (DM, BA, CA, HPN), drugs, nutritional intake, personal habits (e.g., cigarette smoking), and exposure to teratogens.

Physical Examination

Assessing the mother for weight, general appearance, and bruises that may indicate intimate partner violence.

Development Stages

Pre embryonic - 1st 2 weeks; Embryonic - week 3 through 8; Fetal - from week 8 through birth.

Full Term

A pregnancy duration of 37-40 weeks.

Preterm

A pregnancy duration of less than 37 weeks.

Post-term

A pregnancy duration of more than 40 weeks.

Ova

Released from the Graffian Follicle, surrounded by a ring of mucopolysaccharide fluid (Zona pellucida) and a circle of cells (Corona Radiata), moving from the ovary to the fallopian tube.

Sperm

Per ejaculation, 2.5ml of semen containing 50-200 million spermatozoa is released (average 40 million sperm/ejaculation).

Capacitation

Changes in the plasma membrane of the sperm head to reveal sperm binding receptor sites before penetrating into the corona radiata.

Steps in Fertilization

1. Sperm penetrates egg using enzymes to break through the egg's protective layer. 2. The nuclear membrane of both sperm and egg ruptures, combining genetic material.

Cleavage

The mitotic division of a fertilized egg or zygote.

Morula

A ball of cells made up of approximately 50 cells formed as the zygote moves through the fallopian tube.

Blastocyst

A hollow structure formed from the morula as it moves into the uterus.

Implantation

The process where the blastocyst secretes an enzyme to break through the uterus wall, embedding the fertilized egg into the uterine lining.

Decidua

What the endometrium is called after implantation.

Gastrulation

The process where the cluster of cells known as the blastocyst divides into 3 layers.

Ectoderm

The outer layer that develops into the nervous system, lining of the mouth, nostrils, anus, and epidermis of skin.

Mesoderm

The middle layer that develops into bones, muscles, blood and blood vessels, reproductive and excretory systems, and the inner layer of skin.

Endoderm

The inner layer that develops into the lining of the digestive tract, trachea, bronchi, lungs, liver, pancreas, thyroid, parathyroid, thymus, and urinary bladder.

Amniotic Sac

The membrane formed by the outer layer of the blastocyst that protects and nourishes the developing embryo.

Chorion

Outer fetal membrane, formed from the trophoblast (maternal side of placenta).

Amnion

Originates in the blastocyst during early stages of development, expands as the fetus grows until it slightly adheres to the chorion (fetal side of placenta).

Amniotic Fluid

Formed by the secretion of amniotic cells, lungs and skin of fetus, and fetal urine; 98% water, contains glucose, protein, sodium, urea, creatinine, lanugo, vernix caseosa; slightly alkaline, replaced approximately every 3 hours.

Functions of Amniotic Fluid

Never stagnant; serves to protect fetus, shields against pressure, equalizes the pressure around the fetus, cushions the fetus from external compression, protects from temperature changes, provides constant temperature and fluid for the fetus to swallow, protects umbilical cord, allows freedom of movement for the fetus, lubricates the membrane and the fetus.

Placenta

Formed by the chorionic villi at the base of the implanted fertilized ovum and the decidua basalis, and the endometrium at the side of implantation.

Nutrient Exchange

Nutrients and oxygen are exchanged through diffusion; the placenta is the embryo's organ of respiration, nourishment, and excretion.

Fully Functional Placenta

The placenta is fully functional by the 12th week of pregnancy.

Maternal Side of Placenta

Irregular and divided into subdivisions called cotyledons - DUNCAN.

Fetal Side of Placenta

Covered by amnion, so it is smooth and shiny - SCHULTZ.

Umbilical Cord

A structure that connects the fetus to the placenta, has 2 arteries and 1 vein.

Umbilical Arteries

Carry deoxygenated blood from the fetus to the placenta.

Umbilical Vein

Carries oxygenated blood to the fetus, along with nutrients and hormones.

Foramen Ovale

Connects the left and right atria, bypassing fetal lungs; obliterated after birth to become fossa ovalis.

Ductus Venosus

Carries oxygenated blood from umbilical vein to inferior vena cava, bypassing fetal liver; becomes ligamentum venosum after birth.

Ductus Arteriosus

Carries oxygenated blood from pulmonary artery to aorta, bypassing fetal lungs.

Fetal Circulation

In the fetal circulatory system, the umbilical vein transports blood rich in O2 and nutrients from the placenta to the fetal body.

Blood Flow from Placenta

Blood from the placenta is carried to the fetus by the umbilical vein; about half enters the fetal ductus venosus and is carried to the inferior vena cava.

Right Atrium Blood Flow

Most of the blood flows through the foramen ovale directly into the left atrium from the right atrium, thus bypassing pulmonary circulation.

Left Ventricle Blood Flow

The continuation of this blood flow is into the left ventricle, and from there it is pumped through the aorta into the body.

Umbilical Vein Function

Brings oxygenated blood coming from the placenta to the heart and liver; becomes ligamentum teres.

Umbilical Arteries Function

Carry unoxygenated blood from the fetus to placenta; become umbilical ligaments after birth.

1st trimester

12 weeks.

2nd trimester

13 to 27 weeks.

3rd trimester

28 to 40 weeks.

Embryonic stage

Week 4 - (wt 0.4g, length is 4-6mm), half the size of a pea, brain differentiates, G.I. tract begins to form, limbs buds appear.

Week 5

Cranial nerves present, muscles have innervation (L 6-8mm).

Week 6

Fetal circulation established. Liver produces red blood cells, CNS forms, primitive kidney forms, lung buds present, cartilage forms, primitive skeleton forms, muscles differentiate.

Development occurs in systematic manner

From head to toe, from proximal to distal, from general to specific.

Right atrium

The chamber of the heart that receives deoxygenated blood from the body.

Right ventricle

The chamber of the heart that pumps deoxygenated blood into the pulmonary artery.

Pulmonary artery

The artery that carries deoxygenated blood from the right ventricle to the lungs.

Maternal circulation

The system through which the mother's blood circulates, allowing for the exchange of gases and nutrients with the fetus.

Carbon dioxide

A waste product from the fetus that is taken up by the placenta.

Ligamentum venosum

The remnant of the ductus venosus after birth.

Week 7

Eyelids form, palate and tongue form, stomach formed, diaphragm formed, arms and legs move (L 22-28mm).

Week 8

Resembles human being, eyes move to face front, heart development complete, hands and feet well formed; bone cells begin to replace cartilage, all body organs have begun forming (wt-2g, L 3cm).

End of Week 8

The embryo is called a fetus and all of the major structures are present.

Fetal Stage Week 9

Fingers and toenails form; eyelids fuse shut.

Fetal Stage Week 10

Head growth slows, islets of langerhans differentiated, bone marrow forms, RBC produced; bladder sac forms, kidneys make urine (wt-14g, L 5-6cm, C - H).

Fetal Stage Week 11

Tooth buds appear, liver secretes bile; urinary system functions, insulin forms in pancreas.

Fetal Stage Week 12

Lungs take shape, palate fuses, heart beat heard with Doppler, ossification established, swallowing reflex present; external genitalia, male or female distinguished.

Fetal Stage Week 16

Meconium forms in bowels, scalp hair appears, frequent fetal movement, skin thin and pink, sensitive to light, 200 ml of amniotic fluid.

Fetal Stage Week 20

Myelination of spinal cord begins, peristalsis begins, lanugo covers body; vernix caseosa covers body, brown fat deposit begins, swallows and sucks amniotic fluid, heart beat heard by fetoscope, hands can grasp, regular schedule of sucking, kicking and sleeping (wt 435g, L 19cm).

Fetal Stage Week 24

Alveoli present in lungs/begin producing surfactant, eyes completely formed, eyelashes and eyebrows appear, many reflexes appear, (+) chance of survival if born.

Fetal Stage Week 28

Subcutaneous fat deposits begin; lanugo begins to disappear, nails appear, eyelids open and close; testes begin to descend.

Fetal Stage Week 32

More reflexes present, CNS directs rhythmic breathing movement/partially controls body temperature, begins storing iron, calcium, phosphorus; ratio of lung surfactant lecithin and sphingomyelin is 1.2:2.

Fetal Stage Week 36

A few creases on soles of feet, skin less wrinkled, fingernails reach fingertips, sleep-wake cycle fairly definite, transfer of maternal antibodies.

Fetal Stage Week 38

L/S ratio 2:1.

Fetal Stage Week 40

Lanugo only on shoulders and upper back; creases cover sole, vernix mainly in folds of skin, ear cartilage firm, less active, limited space, ready to be born.

Cardiovascular System

Primitive heart begins to beat on the 21st day following conception, the 1st to function in the embryo.

Congenital Malformation

May develop during the 6th to 8th weeks.

Fetal Heart Rate Assessment

Methods include fetoscope and Doppler.

Daily Fetal Movements Count

Fetal kick count; quickening occurs approx. 18 - 20 weeks of pregnancy, peaks 28 to 38 weeks.

Rhythm Strip Testing

Assessing FHR for whether a good baseline rate and both long- and short-term variability are present.

Nonstress Testing

Measures the response of the FHR to fetal movement.

Ultrasonography

Measures the response of sound waves against solid objects.

Doppler Umbilical Velocity

Measures the velocity at which red blood cells in the uterine and fetal vessel travel.

Placental Grading

Placenta can be graded by ultrasound based on the particular amount of calcium deposited at its base.

Grade 0

Placental grade for between 12 and 24 weeks.

Grade 1

Placental grade for 30 to 32 weeks.

Grade 2

Placental grade for 36 weeks.

Grade 3

Placental grade for 38 weeks; suggests that the fetus is mature.

Amniotic Fluid Volume

Measure the amount of amniotic fluid to estimate fetal health.

Normal Amniotic Fluid Volume

Between 28 and 40 weeks, the total pockets of amniotic fluid revealed by sonogram average 12 to 15 cm.

Hydramnios

Amount of amniotic fluid greater than 20 to 24 cm, possibly caused by inability of the fetus to swallow.

Oligohydramnios

Amount of amniotic fluid less than 5 to 6 cm, possibly caused by poor perfusion and kidney failure.

Teratogen

Any exposure that can cause harm to an unborn or breastfeeding baby.

Risk of Birth Defects

3-5% risk of birth defects increases if exposed to teratogens.

Risk of Miscarriage

25% risk of miscarriage, decreasing to 10% on the eighth week, but increases upon teratogenic exposure.

Alcohol (Chemical Teratogen)

Causes growth & mental retardation, microcephaly, various malformations of the face and trunk, septal defects.

Diethylstilbestrol (DES)

Causes cervical & uterine abnormalities.

Lithium

Causes heart anomalies, including Ebstein's anomaly, tricuspid atresia, and atrial septal defect.

Mercury

Causes mental retardation, cerebral atrophy, spasticity, and blindness.

Streptomycin

Causes hearing loss and auditory nerve damage.

Tetracycline

Causes hypoplasia & staining of tooth enamel and staining of bones.

Thalidomide

Causes limb defects, ear defects, cardiovascular anomalies, tetralogy of Fallot, septal defects, and truncus arteriosus.

Cigarette Smoking

Associated with miscarriage, stillbirth, low birth weight, premature birth, SIDS, possible increase in developmental delays, 1% risk for cleft palate, and failure to thrive.

Rubella Virus

Causes cataracts, deafness, cardiovascular defects, slow growth of fetus, persistent ductus arteriosus, peripheral pulmonary artery stenosis, and septal defects.