NCLEX-RN: Maternal–Newborn Nursing

Maternal–Newborn Nursing: Anatomy and Physiology of Female Reproductive Organs

Focus topic: Maternal–Newborn Nursing

Maternal–Newborn Nursing: Anatomy

Focus topic: Maternal–Newborn Nursing

Female Reproductive Organs
A. Usually divided into two groups: the external and internal genitalia.
B. External genitalia are collectively called the vulva, which consist of:

  • Mons veneris or mons pubis.
  • Labia majora.
  • Labia minora.
  • Clitoris.
  • Vestibule.
  • Urinary meatus.
  • Skene’s ducts and Bartholin’s glands.
  • Hymen.
  • Perineum.

C. Internal organs of reproduction are located in the pelvic cavity.

  • Uterus—muscular organ.
    a. Two major functions.
    (1) Organ in which fetus develops.
    (2) Organ from which menstruation occurs.
    b. Consists of two major parts.
    (1) Corpus (body), which has three layers.
    (a) Perimetrium—external layer.
    (b) Myometrium—middle layer.
    (c) Endometrium—internal layer.
    (2) Cervix, composed of three parts.
    (a) Internal os—opens into body of uterine cavity.
    (b) Cervical canal located between internal and external os.
    (c) External os—opens into vagina.
  • Fallopian tubes—two slender muscular tubes that extend laterally from the cornu of the uterine cavity to the ovaries; they are the passageways through which the ova reach the uterus.
  • Ovaries—two flat, oval-shaped organs located on each side of the uterus. (Correspond to the testes in the male.) Two major functions are:
    a. Development and expulsion of ova.
    b. Primary source for secretion of estrogen and progesterone.
  • Vagina—a canal that extends from lower part of the vulva to the cervix; serves three functions for the body:
    a. Passageway for menstrual blood.
    b. Passageway for fetus.
    c. Organ of copulation.

Skeletal Features of the Pelvis
A. The pelvis is important in obstetrics because it is the passage through which the baby passes during birth. Disproportions between fetus and size of pelvis may make vaginal delivery difficult or impossible.
B. Four bones form the pelvis—two innominate bones, the sacrum, and the coccyx.
C. Divisions of pelvis.

  • False pelvis—shallow extended portion above brim that supports abdominal viscera.
  • True pelvis—portion that lies below pelvic brim and is divided into three sections—the pelvic inlet, the midpelvis, and the pelvic outlet.
  • Four main types of pelvic inlets.
    a. Gynecoid—inlet nearly round or blunt, heart-shaped (45% of women).
    b. Android—inlet wedge-shaped (15% of women).
    c. Anthropoid—inlet oval-shaped (35% of women).
    d. Platypelloid—inlet oval-shaped, transversely (5% or less of women).

D. Measurements of the pelvis.

  • Diagonal conjugate (CD)—distance between sacral promontory and lower margin of symphysis pubis. Measurement greater than 12.5 cm adequate.
  • True conjugate, or conjugate vera (CV)—distance from upper margin of symphysis to sacral promontory. Measurement greater than 11 cm adequate.
  • Tuber-ischial diameter (TI)—transverse diameter of outlet. Measurement greater than 8 cm adequate.
  • Size determination.
    a. X-ray pelvimetry is most accurate means of determining size of pelvis.
    b. X-ray pelvimetry is contraindicated to avoid undue exposure of mother and infant unless pelvic contraction is suspected.

Maternal–Newborn Nursing: Physiology

Focus topic: Maternal–Newborn Nursing

Menstruation and the Menstrual Cycle
Definition: The periodic discharge of blood, mucus, and epithelial cells from the uterus.
A. Menstrual cycle—usually lasts 28 days, but may vary from 21–35 days with ovulation occurring about 14 days before menstruation begins. Usually occurs between the ages of 12 and 45.
B. Hormonal control—depends on adequate functioning of pituitary, ovaries, and uterus.

C. Hypothalamus exerts control through releasing and inhibiting factors.

  • Proliferative phase—estrogen.
    a. Follicle-stimulating hormone (FSH) (secreted during the first half of the menstrual cycle) stimulates the development of the graafian follicle.
    b. As graafian follicle develops, it produces increasing amounts of follicular fluid containing a hormone called estrogen.
    c. Estrogen stimulates buildup or thickening of the endometrium.
    d. As estrogen increases in the bloodstream, it suppresses secretion of FSH and favors the secretion of the luteinizing hormone (LH).
    e. LH stimulates ovulation and initiates development of the corpus luteum.
  • Secretory phase—progesterone.
    a. Follows ovulation, which is the release of mature ovum from the graafian follicle.
    b. Rapid changes take place in the ruptured follicle under the influence of LH.
    c. Cavity of the graafian follicle is replaced by the corpus luteum (mass of yellowcolored tissue).
    d. Main function of the corpus luteum is to secrete progesterone and some estrogen.
    e. Progesterone acts upon the endometrium to bring about secretory changes that thicken and maintain the endometrium during the early phase of pregnancy, should a fertilized ovum be implanted.
  • Menstrual phase.
    a. Corpus luteum degenerates in about 8 days unless the ovum is fertilized.
    b. There is a cessation of progesterone and estrogen produced by corpus luteum and blood levels drop.
    c. Endometrium degenerates and menstruation occurs.
    d. The drop in blood levels of estrogen and progesterone stimulate production of FSH and a new cycle begins.
    e. Basal body temperature dips then rises about a day after ovulation has occurred (0.5–1°F increase).

Maternal–Newborn Nursing: Development of the Fetus

Focus topic: Maternal–Newborn Nursing

Fertilization
Definition: A gamete is a sex cell—ovum or spermatozoon— that has undergone maturation and is ready for fertilization.
A. Fertilization takes place when two essential cells— sperm and ovum—unite.
B. Each reproductive cell (one gamete) carries 23 chromosomes.
C. Sperm carries two types of sex chromosomes, X and Y, which when united with female X chromosome determine the sex of the child (XY—male; XX—female).
D. The site of fertilization is usually in the outer third of the fallopian tubes, and the fertilized egg then descends to the uterus.

Fetal Development
Definition: Embryo is the fertilized ovum during the first 2 months of development. Fetus is the product of conception from 2 months to time of birth. (See Table 12-1.)
A. Implantation occurs about the seventh day after fertilization—nidation.
B. First 8 weeks, when all major organs are developing, is the period of greatest vulnerability.
C. Embryonic development—cells arrange themselves into three layers.

  • Ectoderm—outer layer—gives rise to skin, salivary and mammary glands, nervous system, and other external parts of the body.
  • Endoderm—inner layer—gives rise to thymus, thyroid, bladder, and other small organs and tubes.
  • Mesoderm—layer between the other two—gives rise to urinary and reproductive organs, circulatory system, connective tissue, muscle, and bones.

D. Fetal membranes and amniotic fluid.

  • Fetal membranes—membranes that surround the fetus—are composed of two layers.
    a. Amnion—glistening inner membrane—forms early, about the second week of embryonic development; encloses the amniotic cavity.
    b. Chorion—outer membrane.
  • Amniotic fluid—forms within the amniotic cavity and surrounds the embryo. Usually consists of 500–1000 mL of fluid at the end of pregnancy.
    a. Amniotic fluid is slightly alkaline and contains fetal urine, lanugo from fetal skin, epithelial cells, and sebaceous materials.
    b. Function of the fluid is to provide an optimum temperature and environment for fetus and provide a cushion against injury; fetus also drinks the fluid, probably as much as 600 mL a day near term.
    c. Probably bidirectional maternal–fetal fluid exchange, fetal urine, fetal swallowing, fetal breathing, and/or transfer across chorionic plate. By the end of pregnancy, about 500 mL/hr is replaced (about onehalf total fluid volume).

E. Placental function.

  • Placenta—organ that provides for the exchange of nutrients and waste products between mother and fetus and acts as an endocrine organ.
    a. Provides oxygen and removes carbon dioxide from the fetal system.
    b. Maintains fetal fluid and electrolyte, acid– base balance.
    c. Produces hormones necessary to maintain pregnancy.
  • Placenta develops by the third month.
    a. Formed by union of chorionic villi and decidua basalis.
    b. Fetal surface smooth and glistening.
    c. Maternal surface red and fleshlike.
  • Exchange takes place between mother and fetus through diffusion.
  • Placental function is dependent on maternal circulation.
  • In addition to nutrients, materials passed through placenta are drugs, antibodies to some diseases, and certain viruses. Large particles such as bacteria cannot pass through barrier.
  • Placental transfer of maternal immunoglobulin G gives the fetus passive immunity to certain diseases for the first few months after birth.
  • Hormones produced by the placenta.
    a. Human chorionic gonadotropin (HCG)—detected in urine 15 days after implantation. Hormone stimulates the corpus luteum to maintain endometrium and is the basis of immunological test of pregnancy.
    b. Human placental lactogen (HPL)—effect similar to growth hormone; insulin antagonist; mobilizes maternal free fatty acids.
    c. Estrogen and progesterone.
  • The umbilical cord extends from the fetus to center of the fetal surface of the placenta.
    a. Contains two arteries and one vein.
    b. Protected by mucoid connective tissue termed Wharton’s jelly.
    c. Average cord is 2 cm (0.8 in) diameter and 55 cm (22 in) long.

F. Fetal circulation.

  • Arteries carry venous blood.
  • Vein carries oxygenated blood.
  • Fetal circulation bypass.
    a. Bypass due to nonfunctioning lungs: ductus arteriosus (between pulmonary artery and aorta) and foramen ovale (between right and left atrium).

b. Ductus venosus bypass—due to fetal liver not being used for exchange of waste; connects umbilical artery to inferior vena cava; allows most of fetal blood to bypass liver.
c. Bypasses must close following birth to allow blood to flow through the lungs for respiration and through the liver for waste exchange.

G. Calculation of expected date of delivery or confinement (EDC).

  • Nägele’s rule: Count back 3 months from first day of last menstrual period (LMP) and add 7 days.
    Example: LMP July 18
    EDC April 25
  • Pregnancy usually does not terminate on the exact EDC. If using Nägele’s rule, it may vary from 1 week before to 2 weeks after the expected date. If ultrasound is used (biparietal diameter; BPD) between 17 and 24 weeks’ gestation, the expected date is usually ±5–7 days.

H. Multiple pregnancies (uterus contains two or more embryos). May be the result of fertilization of a single ovum or two separate ova. If division takes place very early in monozygotic twins, two placentas and two chorions are formed.

FETAL GROWTH DURING PREGNANCY

Focus topic: Maternal–Newborn Nursing

Maternal–Newborn Nursing

MULTIPLE PREGNANCIES

Focus topic: Maternal–Newborn Nursing

Maternal–Newborn Nursing

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