Introduction to Pregnancy and Fetal Development

Implantation and Early Pregnancy Signs

Implantation Bleeding: Some women experience very light bleeding when the embryo implants into the side of the uterine wall. * This typically occurs about $10$ days after conception. * Women with naturally light menstrual cycles may mistake this implantation bleeding for a regular period, potentially leading to confusion regarding the pregnancy start date.
Gestational Age vs. Conception Age: There is typically a $2$ -week difference between the gestational age (calculated from the last menstrual period) and the actual age of conception.
Uterine Placement: Ideally, implantation occurs in the upper part of the uterus, known as the fundus. This area provides the best nourishment and oxygen for adequate fetal growth.

Developmental Periods

Embryonic Period: This period spans from Week $3$ to Week $8$ (specifically from Day $15$ to Day $56$ ). * This is a critical time for development. * During Week $3$ , the brain and spinal column begin to form. * Subsequent weeks see the development of the eyes, ears, upper limbs, and lower limbs. * Because organogenesis occurs so early, most women do not realize they are pregnant during this vital stage and may not take necessary precautions.
Fetal Period: This period begins at Week $9$ and continues until the time of birth.

Teratogens and Environmental Hazards

Definition: Teratogens are substances or factors in the environment that can cause harm to the growing embryo/fetus and lead to birth defects.
Examples of Teratogens: * Substances: Alcohol, cigarettes, and drugs (including illegal drugs, over-the-counter medications, and physician-prescribed medications). * Environmental Factors: Lead, mercury, radiation (such as X-rays), and certain hormones. * Infections: German measles (Rubella) and various other maternal infections.
Clinical Screening: It is a nursing responsibility to ask patients of childbearing age if there is any possibility of pregnancy before performing procedures like X-rays to prevent accidental exposure.
Hyperthermia Hazards: High maternal body temperature can be lethal to the embryo because the fetus cannot sweat to cool down inside the uterus. * Pregnant women should be instructed to limit time in hot tubs or saunas to less than $10$ minutes.

Pregnancy Timetables and Trimesters

First Trimester: From conception through the completion of Week $13$ .
Second Trimester: From the start of Week $14$ through the completion of Week $27$ .
Third Trimester: From the start of Week $28$ until birth.
Notation Standards: Pregnancy progress is recorded in weeks and days. * Example: $28 \, 0/7$ or $28 \, 0$ indicates the first day of the $28$ th week. * Example: $28 \, 6/7$ indicates $28$ weeks and $6$ days.

Fetal Development Milestones and Physiology

Quickening: This refers to the mother's first perception of fetal movement. * It is generally first felt between Weeks $16$ and $20$ .
Skin Coverings: At approximately Weeks $16$ to $20$ , the baby is covered in vernix (a protective waxy coating) and lanugo (fine hair). Most of these disappear before birth.
Surfactant Production: Surfactant begins to be introduced between Weeks $20$ and $28$ . * Function: It is produced in the lungs to keep the alveoli open, allowing for breathing and gas exchange. * Clinical Significance: The lungs are the last organ to fully develop. Premature babies often suffer from respiratory distress because they lack sufficient surfactant.

Anatomy and Physiology of the Placenta and Cord

The Placenta: A thick, disc-shaped organ implanted in the uterus (usually the fundus). * Functions: Provides oxygen and nutrients, and removes waste products from the fetal circulation. * Hormone Production: The placenta serves as an endocrine organ, producing: * HCG (Human Chorionic Gonadotropin): Detected in pregnancy tests. * Progesterone: The most important hormone for maintaining the pregnancy; it supports gestation. * Estrogen: Supports fetal and uterine development.
Fetal Membranes: * Amnion: The inner membrane surrounding the baby. * Chorion: The outer membrane. * Chorioamnionitis: An infection of these membranes.
Amniotic Fluid: Provides cushioning against impact (e.g., if the mother falls), regulates temperature, and protects the baby's skin.
The Umbilical Cord: * Contains three vessels: $2$ arteries and $1$ vein. * Mnemonic: "AVA" (Artery, Vein, Artery) or a face with two eyes (arteries) and one mouth (vein). * Function: The vein carries oxygenated blood to the baby; the arteries carry waste and deoxygenated blood back to the placenta. * Wharton's Jelly: A slimy, gelatinous substance inside the cord that protects the vessels.

Fetal Circulation and Genetics

Fetal Circulatory Shunts: Because the lungs and kidneys are not fully functional in utero, the fetus relies on three specific shunts: * Ductus Venosus. * Foramen Ovale: Located between the right and left atrium. * Ductus Arteriosus: Located near the aorta.
Genetics: * Dominant Inheritance: An abnormal gene from one parent that can cause disease even if the other parent's gene is normal. * Recessive Inheritance: Both parents must provide a defective gene for the child to manifest the disease; otherwise, the child is a carrier.
Genetic Counseling: Nurses provide education and information to families. The parents make all final decisions regarding testing and care.

Maternal Health and Mechanical Disruptions

Nutrition and Folic Acid: Essential for preventing neural tube defects. * Pre-pregnancy: $400 \, \mu g$ daily. * During Pregnancy: $600 \, \mu g$ daily.
Oligohydramnios: A condition characterized by a decreased amount of amniotic fluid. * Possible consequences: Clubfoot (feet turned inward), impaired fetal lung development, and the formation of fibrous amniotic bands that can constrict or amputate fetal limbs.
Maternal Infections: Factors that can harm the fetus include Rubella, Toxoplasmosis, Syphilis, Varicella, and Herpes.

Nursing Role and Obstetric Terminology

Nursing Goal: To provide education and encouragement (praise) to ensure a healthy pregnancy and baby.
GTPAL and GPA Systems: * G (Gravida): Total number of pregnancies, regardless of outcome. * Nulligravida: Never pregnant. * Primigravida: Pregnant for the first time. * Multigravida: Pregnant multiple times. * P (Para): Number of pregnancies that reached viability ( $20$ weeks). * Nullipara: Never reached viability. * Primipara: Reached viability once. * Multipara: Reached viability multiple times. * A (Abortion): Includes both elective and spontaneous (miscarriage) abortions. * L (Living): Number of currently living children. * T (Term): Full-term births.
Viability: Defined as at least $20$ weeks gestation or a fetal weight of at least $500 \, g$ .
Birth Classifications: * Preterm: Birth occurring before the completion of Week $37$ (e.g., $37 \, 6/7$ is still considered late preterm). * Term: Birth occurring between Weeks $38$ and $42$ . * Post-term: Birth occurring beyond Week $42$ .

Physiological Changes in the Mother

Uterus: Increases from $2.5 \, oz$ to approximately $2.6 \, lb$ at full term. * Growth occurs in a predictable pattern, allowing providers to estimate gestational age via fundal height. * Braxton Hicks: Irregular "practice" contractions that do not cause labor. They are common in the second trimester.
Breasts: Increase in size; areolas become larger and darker. * Colostrum: The "first milk" produced. It may leak during pregnancy; women are advised not to pump it before birth.
Cervical Signs: * Chadwick's Sign: Bluish purple discoloration of the cervix. * Goodell's Sign: Softening of the cervix. * Hegar's Sign: Softening of the lower uterine segment. * Mucus Plug: Seals the cervix to prevent infection from entering the uterus; it is typically lost at the onset of active labor.
Cardiovascular System: * Blood Volume: Increases by up to $50 \%$ . * Physiologic Anemia: The plasma volume increases more than the red blood cell count, leading to diluted blood (not "true" anemia). * Supine Hypotension: Low blood pressure caused by the heavy uterus compressing the vena cava when the mother lies flat on her back.
Integumentary System: * Chloasma: The "mask of pregnancy" (brownish patches on the face); usually fades after birth. * Linea Nigra: A dark line extending down the center of the abdomen; usually fades. * Striae Gravidarum: Stretch marks on the abdomen, thighs, or breasts; these are permanent and do not disappear, though they may fade.
Endocrine System: * Prolactin: Prepares breasts for lactation. * Oxytocin: Stimulates uterine contractions and the milk ejection reflex.

Signs of Pregnancy (Classification)

Presumptive Signs: Subjective data reported by the mother (e.g., fatigue, nausea). Least reliable as they could be caused by other conditions.
Probable Signs: Objective data observed by an examiner (e.g., positive pregnancy test, Goodell's sign). Highly suggestive but not definitive.
Positive Signs: Definitive evidence of a baby. * Visualization via ultrasound. * Auscultation of fetal heart tones (via Doppler or ultrasound). * Palpation of fetal movement by a trained examiner.