Standards of Care Premature Labor
1 January 2008What is this Condition?
Premature labor is the onset of rhythmic uterine contractions that produce cervical changes (dilation and effacement) after fetal viability but before fetal maturity. It usually occurs between the 26th and 37th week of gestation. Approximately 5 % to 10% of pregnancies end in premature labor, which is responsible for about 75% of newÂborn deaths and many birth defects.
What Causes it?
Possible causes of premature labor may include “breaking water,” or premature rupture of the membranes (occurs in 30% to 50% of cases), preeclampsia, chronic hypertensive vascular disease, excessive amniotic fluid, multiple pregnancy, placenta previa, placental separation, incompetent cervix, abdominal surgery, trauma, structural anomalies of the uterus, infections (such as German measles or toxoplasmosis), congenital adrenal hyperplasia, and death of the fetus.
Other important predisposing factors include:
• Fetal stimulation: Genetically imprinted information tells the fetus that nutrition is inadequate and that a change in environment is required for its well-being; this provokes labor.
• Progesterone deficiency: Decreased placental production of progesterone - thought to be the hormone that maintains pregnancyÂtriggers labor.
• Oxytocin sensitivity: Labor begins because the myometrium becomes hypersensitive to oxytocin, the hormone that normally induces uterIne contractions.
• Myometrial oxygen deficiency: The fetus becomes increasingly proficient in obtaining oxygen, depriving the myometrium of the oxygen and energy it needs to function normally, thus making the myometrium irritable .
• Maternal genetics: A genetic defect in the mother shortens gestation and precipitates premature labor.
What are its Symptoms?
Like labor at term, premature labor produces rhythmic uterine contractions, cervical dilation and effacement, possible rupture of the membranes, expulsion of the cervical mucus plug, and a bloody discharge.
How is it Diagnosed?
Premature labor is confirmed by the combined results of a prenatal history, a physical exam, signs and symptoms, and ultrasound (if available) showing the position of the fetus in relation to the mother’s pelvis. A vaginal exam confirms progressive cervical effacement and dilation.
How is it Treated?
Treatment is designed to suppress premature labor when tests show immature fetal lung development, cervical dilation of less than 1.5 inches (4 centimeters), and the absence of any factors that would prevent continuation of the pregnancy. Measures consist of bed rest and, when necessary, drug therapy.
Beta-adrenergic stimulants, such as Bricanyl, Vasodilan, or, Yutopar, inhibit uterine contractions. Side effects include rapid hear: rate (mother and fetus) and high blood pressure (mother). Magnesium sulfate relaxes the uterine muscle and may produce side effects in the mother, such as drowsiness, slurred speech, flushing, decreased reflexes, gastrointestinal symptoms, and a slow respiratory rate. Side effects in the fetus or newborn may include central nervous system depression, decreased respiratory rate, and decreased sucking reflex.
Maternal factors that jeopardize the fetus and make premature delivery the preferred choice include intrauterine infection, placental separation, placental insufficiency, and severe preeclampsia. Among the fetal problems that become more dangerous as pregnancy nears term are severe isoimmunization and congenital anomalies.
Treatment and delivery require intensive team effort, focusing on:
• continuously assessing the infant’s health through fetal monitoring
• avoiding amniotomy (surgical rupture of fetal membranes), if possible, to prevent cord prolapse or damage to the infant’s tender skull
• maintaining adequate hydration through I.V. fluids
• avoiding sedatives and narcotics that might harm the infant. Morphine or Demerol may be required to minimize pain; these drugs have little effect on uterine contractions but depress central nervous system function and may cause fetal respiratory depression. They should be administered in the smallest dose possible and only when extremely necessary.
Preventing premature labor requires good prenatal care, adequate nutrition, and proper rest. A procedure that reinforces an incompetent cervix may be done at 14 to 18 weeks’ gestation to help prevent premature labor in women with a history of this disorder.
Tagged under:cervical mucus, chronic hypertensive vascular disease, mucus plug, multiple pregnancy, oxygen deficiency Pregnancy Related Disorders
