Physiologic Adaptations to Pregnancy

Physiologic Adaptations to Pregnancy

Uterine Changes

• Uterus undergoes hypertrophy of the uterine wall.
• Vaginal muscles and connective tissue soften, preparing for birth.
• Increased contractibility leads to Braxton-Hicks contractions.
• Cervical glands enlarge to form a mucus plug, acting as a protective barrier.
• Uterus expands and stretches to accommodate the growing fetus.
• Circulatory volume expands, causing vascular congestion.
• Abdominal muscles stretch, which may lead to diastasis recti.
• Increased vascularity in vaginal and cervical glands results in heightened leukorrhea.
• Amenorrhea, or absence of menstruation, occurs during pregnancy.

Hormonal Impact on Smooth Muscle

• Muscle relaxation is facilitated by respiratory estrogen, progesterone, and prostaglandins, potentially causing:
  • Dyspnea and nasal congestion.
  • Epistaxis (nosebleeds).
• Renal effects include increased urine output, incontinence, and a higher risk of urinary tract infections due to progesterone.
• Gastrointestinal changes result in bloating, flatulence, and constipation also linked to progesterone.
• Estrogen and progesterone relax smooth muscles in the cervix and pelvic floor ligaments.

Edema in Lower Extremities

• Edema is caused by increased venous pressure and compression of iliac veins and inferior vena cava during pregnancy.
• Decreased renal flow occurs, particularly in the third trimester.
• Relief methods include:
  • Sleeping on the left side to prevent vena cava compression.
  • Elevating the legs.
  • Staying hydrated and exercising.
  • Wearing compression socks and avoiding prolonged sitting or standing.

Nasal and Sinus Congestion

• Congestion results from elevated levels of estrogen, progesterone, and prostaglandins.

Cardiovascular System Adaptations

• Elevated red blood cell (RBC) count and volume.
• Increased plasma volume leads to decreased hemoglobin concentration.

Fetal Monitoring Techniques

• Daily fetal movement counts (FMC) are recommended after approximately 28 weeks:
  • Options: Two-hour perception of ten distinct movements or one-hour perception of four movements.
  • If no movement is detected post-meal, advise lying on the side.
• Vibroacoustic stimulation (VAS) is used when a non-reactive non-stress test (NST) occurs:
  • Involves applying an artificial larynx on the maternal abdomen; reactive results show FHR increases.
• Contraction stress tests assess fetal heart rate (FHR) response to contractions:
  • A normal (negative) result shows no FHR decelerations with three contractions.
  • An abnormal (positive) result indicates late decelerations during 50% of contractions, suggesting oxygen reserve issues.
• Amniotic Fluid Index (AFI) evaluates amniotic fluid volume to check fetal well-being:
  • Normal range is approximately 8cm to 24cm, while ologohydramnios and polyhydramnios indicate fetal distress.
• A biophysical profile combines NST with ultrasound assessing five indicators and score interpretation.

Diagnosing Pregnancy

Signs of Pregnancy

• Presumptive Signs:

  • Amenorrhea, nausea and vomiting, breast changes (enlargement, tenderness), fatigue, frequent urination, quickening.

• Probable Signs:

  • Uterine growth, skin hyperpigmentation (melasma and linea nigra), and ballottement.

• Positive Signs:

  • Auscultation of fetal heart sounds, palpable fetal movement, and sonographic visualization of fetal structures.

Pregnancy Tests

• Urine pregnancy tests detect human chorionic gonadotropin (hCG), with blood tests providing earlier detection.
• First-morning urine specimens yield the most accurate results for home pregnancy tests.

Preconception and Prenatal Care

Initial Prenatal Visit Components

• Comprehensive health assessment including pregnancy history and physical exam.
• Determine estimated due date (EDD), nutrition assessment, and psychosocial evaluation.
• Standard lab tests including blood type, CBC, RPR, HIV screening, hepatitis B, rubella titer, tuberculosis screen, urinalysis, and cultures.

Teratogenesis

• Teratogenesis refers to congenital malformations due to exposure to harmful agents during development.

Prenatal Education Topics

• Discuss pain relief, postpartum care, early pregnancy discomforts, breastfeeding, signs of labor, and infant care.

Obstetric History Documentation (GTPAL)

• G: Total number of pregnancies.
• T: Term infants (37+ weeks).
• P: Preterm infants.
• A: Abortions (spontaneous or induced).
• L: Living children.

Screening Recommendations

• Gestational diabetes screening occurs at 24-28 weeks.
• Group B Streptococcus (GBS) screening is done at 35-37 weeks.

Infertility Definition

• Defined as the inability to conceive and maintain a pregnancy after six months.

Pregnancy and Fetal Development

Fertilization Location

• Occurs in the outer third of the fallopian tube where sperm and oocyte nuclei merge to form a zygote.

Fetal Circulatory System Structures

• Ductus venosus connects umbilical vein to inferior vena cava.
• Foramen ovale allows blood shunting from right to left atrium.
• Ductus arteriosus connects pulmonary artery to descending aorta, directing most blood to the aorta bypassing the lungs.

Placenta Function and Formation

• Forms from both fetal (chorionic tissue) and maternal (decidual tissue) components.
• Facilitates metabolic and gas exchange via diffusion and active transport, alongside hormone production (hCG, estrogen, progesterone, hPL) essential for pregnancy maintenance.