Taber's Medical Dictionary
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placenta previa

ABBR: PP A placenta that is implanted in the lower uterine segment. There are three types: centralis, lateralis, and marginalis. Placenta previa centralis (total or complete PP) is the condition in which the placenta has been implanted in the lower uterine segment and has grown to completely cover the internal cervical os. Placenta previa lateralis (low marginal implantation) is the condition in which the placenta lies just within the lower uterine segment. Placenta previa marginalis is the condition in which the placenta partially covers the internal cervical os (partial or incomplete PP).
SEE: Nursing Diagnoses Appendix

The condition is more common in multigravidas than primigravidas, and occurs in about 1 in every 200 pregnancies. Slight hemorrhage, recurrent with greater severity, appears in the seventh or eighth month of pregnancy. Gradual anemia, pallor, rapid weak pulse, air hunger, and low blood pressure occur.

Painless bleeding during the last 3 months and a placenta found in the lower portion of the uterus are diagnostic.

The blood supply before and during delivery should be conserved. Postpartum hemorrhage should be prevented or controlled. Anemia should be treated before and after labor. Prevention of sepsis is necessary.

The prognosis for the mother is good with control of hemorrhage and prevention of sepsis. Prognosis for the fetus depends on gestational age and the amount of blood lost, but continuous monitoring and rapid intervention help to prevent neonatal death.

In a calm environment, the patient is told what is happening; then the procedure of vaginal ultrasound is explained. The patient is told that if the ultrasound examination reveals a placenta previa, sterile vaginal examination will be delayed if possible until after 34 weeks' (preferably 36 weeks') gestation (to enhance the chances for fetal survival) and then will be carried out only as a “double-setup” procedure, with all preparations needed for immediate vaginal or cesarean delivery. (If, however, the ultrasound examination reveals a normally implanted placenta, a sterile vaginal speculum examination is performed to rule out local bleeding causes, and a laboratory study is ordered to rule out coagulation problems.)

The patient is maintained on absolute bedrest and under close supervision (usually in the hospital) to extend the period of gestation until 36 weeks, when fetal lung maturity is likely (or can be stimulated to mature 48 hr before delivery). Intravenous access is established using a large-bore catheter, and continuous external electrode fetal monitoring is initiated. Maternal vital signs are closely monitored, and the amount of vaginal bleeding is assessed. The laboratory types and cross-matches blood for emergency use; the number of units is based on the assessment of the particular patient's possible requirements. The patient's hematocrit level is kept at 30% or greater. The patient is prepared physically and emotionally for cesarean delivery; vaginal delivery may be attempted, but only if the previa is marginal, bleeding is minimal, and labor is rapidly progressing.

After delivery, the patient is monitored closely for continued bleeding, which may occur from the large vascular channels in the lower uterine segment, even if the fundus is firmly contracted. Prophylactic antibiotic therapy may be prescribed because of the patient's propensity for infection. Oxytocic drugs are given to control bleeding; packed cells or whole blood also are given. The obstetrical surgery team remains available, in case further intervention is required. The patient's hemodynamic status is monitored continuously, to provide blood and fluid replacement needed to prevent and treat hypovolemia while avoiding hypervolemia.

Although maternal mortality remains a concern, the patient and her family should be assured that this is unlikely but not impossible in most large treatment centers because of the conservative regimen that is followed. A pediatric team is present at delivery to assess and treat neonatal hypoxia, anemia, blood loss, and shock. In the event of fetal distress or death, the family is informed that these are related to detachment of a significant portion of the placenta or to maternal hypovolemic shock, or both. All parents are provided opportunities to be with and touch their (usually premature) neonate in the critical care nursery. In cases of fetal demise, the infant is carefully wrapped and the parents encouraged to hold their baby, and to examine it as they desire. Infant photographs may be taken to provide memories for the family. The patient and family require the health care providers' empathetic concern and support. A social service consultation is set up if financial or home and family care concerns require agency referrals; spiritual counseling is supplied according to the patient's wishes. Reducing maternal anxiety helps reduce uterine irritability, and therefore a mental health practitioner should be consulted if the patient does not respond to nursing interventions (e.g., relaxation techniques, guided imagery) or if the patient's previous coping skills are known to be ineffective.

PLACENTA PREVIA (A) Low implantation. (B) Partial placenta previa. (C) Central (total) placenta previa. (Adapted from Beare, PG: Davis's NCLEX-RN Review, ed 3. FA Davis, Philadelphia, 2001, p 61, with permission.)

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