Medical brain notes 42

  MATERNAL CHANGES BEFORE THE ONSET OF LABOR   As patients approach term, they experience  uterine con-tractions  of increasing strength and frequency. Sponta-neous uterine contractions, which are not felt by the patient, occur throughout pregnancy. Late in pregnancy they become stronger and more frequent, resulting in the patient’s perception of discomfort.  These Braxton Hickscontractions  (false labor) are not associated with dilation of thecervix, however, and do not fit the definition of labor.  It is fre-quently difficult for the patient to distinguish these often uncomfortable contractions from those of true labor. As a result, it is difficult for the physician to determine the true onset of labor by history alone. Braxton Hicks contrac-tions are typically shorter in duration and less intense than true labor contractions, with the discomfort being charac-terized as over the lower abdomen and groin areas. It is not uncommon for these contractions...

  EVALUATION FOR LABOR   Patients should be instructed to contact their health care provider for any of the following reasons: (1) if their con-tractions occur approximately every 5 minutes for at least 1 hour, (2) if there is a sudden gush of fluid or a constant leakage of vaginal fluid (suggesting rupture of membranes),   if there is any significant vaginal bleeding, or (4) if there is significant decrease in fetal movement.     Initial Evaluation   At the time of initial evaluation, the prenatal records are reviewed to (1) identify complications of pregnancy up to that point, (2) confirm gestational age to differentiate preterm labor from labor in a term pregnancy, and  review pertinent laboratory information. A focused history helps in determining the nature and frequency of  the patient’s contractions, the possibility of spontaneous rupture of membranes or significant bleeding, or changes in maternal or fetal status.   A focused review o...

  STAGES OF LABOR   Although labor is a continuous process, it is divided into four functional stages because each has differing physio-logical activities and requires differing management.   The  first stage of labor  is the interval between the onset of labor and full cervical dilation (10 cm). The first stage is further divided into two phases: (1) The  latentphase  of labor encompasses cervical effacement and early dilation, and (2) the  active phase  of labor, during which more rapid cervical dilation occurs, usually begin-ning at approximately 4 cm.   The  second stage of labor  encompasses complete cer-vical dilation through the delivery of the infant.   The  third stage of labor  begins immediately after delivery of the infant and ends with the delivery of the placenta.   The  fourth stage of labor  is defined as the immediate postpartum period of approximately 2 hours after deliv-ery of th...

  MECHANISM OF LABOR   The  mechanisms of labor  (also known as the  cardinalmovements of labor  [Fig. 8.6]) refer to the changes of theposition of the fetus as it passes through the birth canal. The fetus usually descends to where the occipital portion of the fetal head is the lowermost part in the pelvis, and it rotates toward the largest pelvic segment.  Because vertex presentation  occurs in 95% of term labors, the cardinal movements of labor are defined relative to this presentation.    To accommodate to thematernal bony pelvis, the fetal head must undergo several movements as it passes through the birth canal. These movements are accomplished by means of the forceful con-tractions of the uterus. These cardinal movements of labor do not occur as a distinct series of movements, but rather as a group of movements that overlap as the fetus accommo-dates and moves progressively through the birth canal. These movements are   · ...

  NORMAL LABOR AND DELIVERY   Ideally, a pregnant woman has a principal, designated health care provider. Beginning with admission to the labor and delivery area, the obstetric team monitors the patient’s progress. Once the patient is in active labor, her provider should be readily available.   General Management   AMBULATION AND POSITION IN LABOR AND AT DELIVERY   Walking may be more comfortable than being supine dur-ing early labor. Women in early labor are confined to bed if they are too uncomfortable to move about safely or if care  maneuvers require it.     Supine labor is common in the United States. The left lateral position keeps the uterus off the infe-rior vena cava; this obstructs venous return, thence cardiac output, leading to hypotension (supine hypotensive syn-drome).  The dorsal lithotomy position is most commonly usedfor spontaneous and operative vaginal delivery in the United  “birthing chairs,” on labor balls, or in va...

  Control of Pain   Management of discomfort and pain during labor is an essential part of good obstetric practice. Some patients tolerate pain by using techniques learned in childbirth preparation programs. It is important that bedside staff be knowledgeable about these pain management techniques and be supportive of the patient’s decisions. Unless con-traindicated, pharmacologic analgesics to ameliorate pain of contractions should be made available on request to women in labor.   During the first stage of labor, pain results from the contraction of the uterus and dilation of the cervix. This pain travels along the visceral afferents, which accompany sympathetic nerves entering the spinal cord at T-10, T-11, T-12, and L-1. As the fetal head descends, there is also dis-tension of the lower birth canal and perineum. This pain is transmitted along somatic afferents that comprise por-tions of the pudendal nerves that enter the spinal cord at S-2, S-3, and S-4. To provide rel...