Premature Birth
From Encyclopedia of Sex and Sexuality
The classic term “prematurity” refers to a birth weight of less than 2,500 grams. The more correct term is “preterm” for any infant born before thirty-seven weeks of gestation (266 days from the first day of the mother’s last menstrual period). Low birth weight (LBW) includes infants who weigh less than 2,500 grams at birth and very low birth weight (VLBW) refers to infants weighing less than 1,500 grams at birth (regardless of gestational age).
Preterm infants are at risk for specific diseases relating to the immaturity of various organ systems. The frequency of these complications varies with gestational age: the earlier the infant is born, the greater the risk. The risk decreases with a gestational age greater than twenty-eight weeks.
Preterm infants are at increased risk for serious neurodevelopmental handicaps such as cerebral palsy, mental retardation, and seizure disorders. They may also be at risk of experiencing chronic pulmonary disease or severe illness in general. Besides prolonged hospitalization at birth, a substantial portion of VLBW infants are rehospitalized during the first year of life. There is also concern that preterm birth disrupts maternal-infant bonding, which can have a major impact on the family function. With advances in medical and nursing care and technology, more premature infants of a younger gestational age are surviving, and the number of healthy survivors is rising.
Studies of neurological outcome are, of necessity, reviews of prior neonatal practices. In general, one to two years of careful follow-up examinations are sufficient to detect major handicaps. Longer studies are needed to identify problems with school performance or behavior.
Various factors are associated with increased preterm delivery. Socioeconomic status, race, maternal age (eighteen years or less or forty years or more), low prepregnancy weight, and smoking are major risk factors. Maternal smoking level correlates with perinatal mortality, preterm delivery, premature rupture of membranes, and bleeding during pregnancy. Women who work during pregnancy do not deliver more preterm infants as a whole than nonworking women. Women with a history of poor pregnancy outcomes who work long hours or who work in occupations associated with fatigue may be predisposed to preterm delivery. Coitus and/or orgasm during pregnancy have not been linked to preterm delivery.
Women with poor prenatal care are more likely to deliver before term regardless of their social class. Socially disadvantaged women appear to gain the most from prenatal care. Maternal nutritional status and weight gain in pregnancy are commonly assumed to relate to neonatal birth weight and preterm delivery. Certainly, extremes of malnutrition and starvation lead to a decrease in birth weight.
The incidence of preterm birth correlates strongly with prior obstetric outcome. The history of one previous preterm birth is associated with a recurrence risk of 17 to 40 percent, with the risk factor increasing with the number of preterm births and decreasing with the number of term deliveries. Women with uterine malformations are also at greater risk of preterm delivery. The risk varies with the abnormality. Cervical incompetence often leads to painless second trimester cervical dilation and miscarriage. Once dilation has occurred, preterm labor and/or rupture of membranes can occur, making it difficult to establish the etiology of the preterm birth.
Identifying women at high risk of experiencing preterm labor is a necessary first step in preventing preterm births. Identification permits the physician to monitor the selected patients more carefully and to intervene should problems arise during pregnancy. Once identified, the question arises if there are additional approaches above routine prenatal care that can prevent preterm labor and birth in these high-risk patients. A number of treatment regimes have been proposed, including the use of progesterone supplementation, tocolytic agents (medications that suppress uterine contractions), cerclage (stitching of the cervix during pregnancy), and bed rest. Most high-risk women are usually treated with a combination of two or more of these regimes.
No other fetus benefits more from fetal monitoring than the very premature. Careful and intensive surveillance of these fetuses has been found to result in significantly improved outcomes.
