Pregnancy and Childbirth Notes

Pregnancy and Childbirth

  • Gestation (pregnancy)
    • Averages 266 days from conception to childbirth (38 weeks).
  • Gestational calendar
    • Measured from the first day of the woman’s last menstrual period (LMP) (40 weeks).
  • Birth prediction
    • Occurs 280 days from LMP.
    • Divided into three, three-month intervals called trimesters.

Maternal Changes During Pregnancy

  • Uterus:
    • Nearly fills the abdominal cavity.
  • GI tract:
    • Compressed, causing heartburn and constipation.
  • Bladder:
    • Pressure leads to increased frequency and urgency of urination.
  • Vena cava:
    • Compression causes varicose veins and edema in the legs.
  • Renal vessels:
    • Compression causes renal hypertension.

Physiological Changes During Pregnancy

  • Cardiovascular changes:
    • Increased cardiac output by 20-30% due to the placenta.
    • Increased heart rate by 15%.
    • Increased blood volume by 30-50%.
  • Respiratory changes:
    • Increased tidal volume by 30%.
    • Decreased expiratory reserve volume and airway resistance.
    • Increased minute respiratory volume as O2O_2 needs increase.
  • Reproductive system changes:
    • Uterus size increases from 80g to 1200g through hyperplasia (more cells) and hypertrophy (larger cells).
  • Urinary system changes:
    • Increased glomerular filtration rate (GFR) by 40-50%.

Pregnancy-Induced Hypertension (PIH)

  • Elevated blood pressure.
  • Preeclampsia:
    • Elevated blood pressure with proteinuria.
    • Frequently includes edema (not diagnostic).
    • Severe symptoms include headaches, blurry vision, epigastric pain.
    • May progress to HELLP syndrome (Hemolysis, Elevated Liver enzymes, Low Platelets).
  • Eclampsia:
    • Progression of preeclampsia with increased proteinuria and seizures.
    • 2% mortality rate.

Exercise and Pregnancy

  • Early pregnancy:
    • Avoid excessive exercise and heat buildup due to links to neural tube defects.
  • Moderate exercise:
    • Beneficial effects.
    • No evidence of inadequate blood flow to the placenta.

Prenatal Development Terminology

  • Conceptus: Less than 2 weeks old.
  • Embryo: From 3 to 8 weeks old.
  • Fetus: 9 weeks to birth.
  • Neonate: Newborn up to 6 weeks old.
  • Blastocyst:
    • Inner cell mass (developing embryo).
    • Outer cell mass (trophoblast).
  • Implantation:
    • Attachment of conceptus to endometrium.
  • Placenta:
    • Both maternal and trophoblastic tissue.
  • Embryo attachment:
    • Attached to the placenta by the umbilical cord and floats in amniotic fluid.

Hormones of Pregnancy (1)

  • HCG (human chorionic gonadotropin):
    • Secreted by trophoblast within 9 days of conception.
    • Prevents involution of corpus luteum.
  • Estrogens:
    • Increases to 30 times normal before birth.
    • Corpus luteum is the source for the first 12 weeks until the placenta takes over.
    • Causes uterine, mammary duct, and breast enlargement.

Hormones of Pregnancy (2)

  • Progesterone:
    • Secreted by placenta & corpus luteum.
    • Suppresses secretion of FSH & LH, preventing follicular development.
    • Prevents menstruation & thickens endometrium.
    • Stimulates development of acini in breast tissue.
  • HCS (human chorionic somatomammotropin):
    • Also called human placental lactogen.
    • Secreted from the placenta in direct proportion to its size.
    • Decreases mother’s glucose usage and increases release of fatty acids.
  • Other endocrine organs:
    • Thyroid gland increases 50% in size, increasing the BMR of the mother.
    • Parathyroid glands enlarge and stimulate osteoclasts to release additional calcium from the mother’s bones.
    • Aldosterone secretion leads to fluid retention, increasing the mother’s blood volume.

Adjustments to Pregnancy

  • Digestive System, Nutrition, & Metabolism:
    • Nausea during the first few months.
    • Constipation & heartburn due to decreased intestinal motility and pressure on the stomach.
    • Basal metabolic rate increases, which may stimulate appetite.
    • Healthy weight gain is 25-35 lbs. (for a woman within the recommended BMI range).
    • The placenta stores nutrients prior to the 3rd trimester.
    • High demand for protein, iron, calcium, & phosphates.
    • Supplemental vitamin K reduces the risk of neonatal hemorrhages in the brain during delivery.
    • Early (before pregnancy) supplemental folic acid prevents neurological disorders like spina bifida and anencephaly.
  • Circulatory and Respiratory Systems:
    • Mother’s blood volume rises 30% due to fluid retention & hematopoiesis.
    • By full term, the placenta requires 625 mL of blood/minute.
    • Cardiac output rises about 30% by 27 weeks.
    • Pressure on large pelvic blood vessels can produce hemorrhoids and varicose veins.
    • Minute respiratory ventilation increases about 50% due to the demands of the fetus and higher maternal metabolic rate.
    • Ventilation is adjusted to keep PCO2PCO_2 lower than normal.
    • Respiratory rate increases due to the inability to breathe as deeply.
  • Urinary & Integumentary Systems:
    • Aldosterone & steroids of pregnancy promote salt and water retention.
    • GFR increases by 50%, & output is slightly elevated – enabling women to dispose of additional metabolic wastes.
    • Bladder compression increases the frequency of urination.
    • Skin must grow; dermal stretching causes stretch marks.
    • The linea alba may become a dark line (linea nigra).
    • Blotchy darkening of the skin over the nose & cheeks may temporarily occur (chloasma or “mask of pregnancy”).

Childbirth & Uterine Contractility

  • Parturition: the process of giving birth via contraction of the mother’s uterine & abdominal muscles (GPA nomenclature example: G1P0A0 = nullparity).
  • Braxton Hicks: weak contractions occur throughout gestation = false labor.
  • Progesterone inhibits contractions, while estrogen stimulates contractions.
  • Nearing full term:
    • The posterior pituitary releases more oxytocin.
    • The uterus produces more receptors – directly stimulates myometrial contractions. Stimulates fetal membranes to produce prostaglandins, which are synergists of oxytocin.
  • The fetus secretes cortisol, enhancing estrogen secretion & oxytocin stimulating prostaglandin secretion.

True Versus False Labor

  • True labor:
    • Contractions occur at regular intervals producing pain.
    • Back pain increases with walking.
    • Dilation of the cervix (due to the presence of prostaglandins) with a discharge of blood-containing mucus in the cervical canal.
    • Can be induced by cervical application of misoprostol (synthetic prostaglandin) and IV Pitocin (synthetic oxytocin).
  • False labor:
    • Produces pain at irregular intervals, but there is no cervical dilation.

Labor Contractions

  • Contractions begin 30 minutes apart and eventually occur every 1-3 minutes.
    • Periodically relax to increase blood flow to the placenta (fetus).
    • Contractions are strongest in the fundus & body, pushing the fetus into the cervix.
  • Self-amplifying cycle of stretch & contraction (reflex):
    • Positive feedback cycle increases contractions.
    • cervical stretching leads to oxytocin secretion leading to uterine contraction leading to cervical stretching.
    • The 2nd reflex arc is from the uterus leading to the spinal cord leading to abdominal skeletal muscles, producing contractions that help expel the fetus.
  • Pain of labor:
    • Ischemia of myometrium.
    • Stretching of the cervix, vagina, & perineum (episiotomy prevents tearing).
    • Large head & narrow pelvic outlet due to bipedal locomotion.

Stages of Labor -- Early Dilation Stage

  • Widening of the cervical canal by effacement (thinning) of the cervix to reach 10 cm, the diameter of the fetal head (epidural optional at 4 - 5 cm).
  • Rupture of fetal membranes & loss of amniotic fluid.

Stages of Labor -- Late Dilation Stage

  • Dilation reaches 10 cm in 24 hours or less in primipara (first baby) & in as little as a few minutes in multipara.

Stages of Labor -- Expulsion Stage

  • Time from baby’s head entering vagina until delivery, which may last up to 30 minutes.
  • The Valsalva maneuver helps to expel the fetus.

Stages of Labor -- Placental Stage

  • Uterine contractions continue, causing placental separation (delivered within 30 minutes).
  • 400 - 500 mL blood loss is normal, but postpartum hemorrhaging occurs if expulsion is not completed.

Dystocia & Caesarean Section

  • Dystocia = difficult labor:
    • Due to fetal position or size.
    • Breech presentation is butt or feet first in the birth canal.
  • Caesarean section (C-section):
    • Can be planned due to incompatibility between the size of the fetus and the birth canal, position of the placenta, or position of the fetus.
    • Can be emergent due to dystocia or indications seen in fetal heart monitoring.
    • Horizontal incision through the lower abdominal wall and uterus.
    • VBAC (vaginal birth after caesarean) possible but only in a facility equipped to handle uterine rupture. Becoming much more common and accepted.
    • Loss of up to a liter of blood is normal.

Puerperium

  • The first 6 weeks after delivery = puerperium.
  • The mother’s anatomy & physiology return to normal.
    • Shrinkage of the uterus is called involution.
      • At pregravid weight in 4 weeks.
      • Accomplished by autolysis by lysosomal enzymes.
    • Vaginal discharge is called lochia.
    • Breastfeeding promotes involution:
      • Suppresses estrogen secretion.
      • Stimulates oxytocin, which causes myometrial contraction.

Development of Mammary Glands

  • Lactation = synthesis and ejection of milk from mammary glands.
  • High estrogen levels in pregnancy cause ducts to grow and branch.
  • Progesterone stimulates budding & development of the acini at the ends of the ducts.

Colostrum & Milk Synthesis

  • Colostrum forms in late pregnancy:
    • Similar to breast milk, but contains 1/3 less fat and is thinner.
    • Nutrition for the first 1 to 3 days after birth.
    • Contains IgA, which protects from gastroenteritis.
  • Synthesis is promoted by prolactin (from the pituitary):
    • Synthesis of the hormone begins 5 weeks into pregnancy; by full term, it is 20x the normal level.
    • Steroid hormones from the placenta oppose it until birth.
  • At birth, prolactin secretion drops to nonpregnant levels, but sharply increases 20 times with nursing events.
  • Without continuous nursing, production stops in 1 week.
  • 5-10% of women become pregnant again while nursing:
    • Inhibition of GnRH & reduced ovarian cycling.
    • Without continuous nursing decreased prolactin levels allow normal ovarian cycling.

Milk Ejection

  • Milk ejection or let-down is controlled by a neuroendocrine reflex:
    • The infant’s suckling stimulates sensory receptors in the nipple, signaling the hypothalamus & posterior pituitary to release oxytocin.
    • Oxytocin stimulates myoepithelial cells.
      • Myoepithelial cells surround each gland acinus.
      • Epithelial cells are packed with actin.
      • Contract like smooth muscle to squeeze milk into the duct.
    • Milk flow within 30-60 seconds after suckling begins.
  • Oxytocin release is triggered by other stimuli such as hearing a baby’s cry or touching the genitals.

Breast Milk

  • Cow’s milk is not a good substitute for human milk (not until 12 months):
    • 1/3 less lactose but 3 times as much protein.
    • Harder to digest & more nitrogenous waste (diaper rash).
  • Colostrum & milk have a laxative effect that clears the intestine of meconium (green, bile-filled fecal material in the newborn).
  • Breast milk supplies antibodies & colonizes the intestine with beneficial bacteria.
  • A nursing woman can produce 1.5L per day:
    • Increase calorie intake by 300.
    • Increase Ca+2Ca^{+2} & vitamin D.

Benefits of Breast-feeding

  • Faster & better absorption of the “right” nutrients.
  • Beneficial cells:
    • Functional white blood cells.
      • Neutrophils help ingest bacteria in the baby’s gut.
      • Macrophages produce lysozymes.
      • Plasma cells provide antibodies, preventing gastroenteritis.
  • Decreased incidence of diseases later in life:
    • Reduction in allergies, respiratory & GI infections, ear infections, & diarrhea.
  • Parent-child bonding.
  • Infant in control of intake.

Nursing and Childbirth

  • Nursing of first-born twin speeds the birth of the second child:
    • Stimulates the release of oxytocin.
  • Nursing of only child:
    • Promotes expulsion of the placenta.
    • Helps control hemorrhage after birth.
    • Helps the uterus return to normal size.

Aging Female Reproductive System

  • Hormone-directed sexual characteristics start to develop at puberty.
  • The reproductive cycle occurs once/month from menarche (10-14) until menopause (most commonly between 48-52).
  • Fertility declines with age:
    • Decreasing number of viable follicles.
    • Less frequent ovulation.
    • Declining ability of the uterus to support a young embryo.
  • Menopause is the cessation of menstruation:
    • No remaining follicles to stimulate estrogen secretion.
      • Causes “pelvic relaxation” of ligaments, leading to incontinence, organ prolapse (example: cystocele, aka bladder prolapse), and fistula formation (example: rectovaginal fistula).
      • Osteoporosis, hot flashes, mood swings, and organ atrophy.

Aging Male Reproductive System

  • The decline in reproductive function is more subtle (capacity may remain into the 90s).
  • Decline in testosterone at 55 leads to:
    • Reduced muscle synthesis.
    • Fewer viable sperm.
    • Reduced sexual desire.
  • Enlargement of the prostate (Benign Prostatic Hypertrophy, or BPH):
    • 1/3 of males over 60.
      • Frequent urination, decreased force of stream, bed-wetting, & sensation of incomplete emptying.

Sexually Transmitted Diseases (STDs)

  • On the increase in the United States.
  • Chlamydia:
    • Bacteria are often asymptomatic; leads to sterility from scar tissue formation (most common cause of Pelvic Inflammatory Disease, PID).
  • Gonorrhea:
    • Bacteria with discharge are common; blindness if the newborn is infected during delivery, the second most common cause of PID.
  • Syphilis:
    • Bacteria with painless sores (chancre).
      • The 2nd stage involves all organs.
      • The 3rd stage (tertiary syphilis) has apparent organ degeneration (neurosyphilis).
  • Genital Herpes:
    • Virus (herpes simplex virus HSV), incurable, painful blisters.
  • Genital Warts:
    • Virus (human papilloma virus HPV), associated with cervical cancer, vaccine available.
  • AIDS & Hepatitis C:
    • Viruses.

Testicular Cancer

  • The most common cancer in the age group 20-35 (one of the most curable).
  • Begins as a problem with spermatogenic cells within the seminiferous tubules.
  • The sign is a mass within the testis.
  • Regular self-examination is important.

Prostate Cancer

  • The most common male cancer. The second most common cause of male cancer death (after lung cancer).
    • Treatment is surgery, radiation, hormonal and chemotherapy.
  • Blood test for prostate-specific antigen (PSA):
    • Enzyme of epithelial cells.
    • The amount increases with enlargement (indication of infection, benign enlargement, or cancer).
  • Over 40 yearly Digital Rectal Exam (DRE) of the prostate gland.
  • Acute or chronic prostatitis:
    • Infection of the prostate-causing swelling, tenderness, & blockage of urine flow.
    • Treat with antibiotics.

Endometriosis

  • Growth of endometrial tissue outside of the uterus:
    • Tissue discharged from the open-end of the uterine tubes during menstruation.
    • Can cover ovaries, the outer surface of the uterus, colon, kidneys, and bladder.
  • The problem is tissue responds to hormonal changes by proliferating, then breaking down & bleeding.
    • Causes pain, scarring, & infertility.

Breast Cancer

  • 1 out of every 8 American women is affected, rare under 30.
  • Tumors begin with cells from mammary ducts; may metastasize by way of lymphatics.
  • Symptoms may include a palpable lump, skin puckering, skin texture, & drainage from the nipple, “orange peel” skin from pressure on Cooper’s ligaments.
  • Most breast cancer is nonhereditary; some are stimulated by estrogen.
  • Risk factors include aging, family history, lifetime estrogen & progesterone exposure, BRCA 1 & BRCA 2 mutations, ionizing radiation, carcinogenic chemicals, alcohol, smoking & fat intake (70% lack risk factors).

Ovarian Cancer

  • The most common cause of gynecological deaths, excluding breast cancer.
  • Difficult to detect before metastasis (vague, nonspecific symptoms like loss of appetite).
  • Positive CA-125 blood test, but is not used for screening.
  • Risk factors: over 50, white, family history, nulliparity, first pregnancy after 30, diet (high fat, low fiber and lack of vitamin A), asbestos & talc.
  • Early symptoms unremarkable: heartburn, nausea, bloating, loss of appetite, etc.

Cervical Cancer

  • Starts as cervical dysplasia (change in shape, growth & number of cells – ASCUS Atypical Squamous Cells of Undetermined Significance).
  • May progress to cervical cancer (slow-growing).
  • Detected in a Pap smear; cervical cancer was the leading cause of cancer death in women before the Pap smear. Now the least common. A good example of the successful implementation of public health policy.
  • Linked to genital warts, herpes, and a large number of sexual partners at an early age.

Yeast Infection

  • Candida albicans is a yeastlike fungus that grows on mucous membranes.
  • Causes vulvovaginal candidiasis or vaginitis:
    • Inflammation of the vagina.
    • Severe itching and pain.
    • Yellow discharge with odor.
  • More likely after antibiotic therapy for some other disease.
  • More likely in diabetics.