Preterm labor refers to the onset of uterine contractions of sufficient strength and frequency to effect progressive dilatation and effacement of cervix between 20 and 37 weeks of gestation. Preterm labor complicates 5-10% of pregnancies and is a leading cause of neonatal morbidity and mortality worldwide. It is a major public health problem in terms of loss of life, long-term disability (cerebral palsy, blindness, deafness, chronic lung disease) and health care costs both in the developing and the developed world. In the USA, approximately 450,000 (11.5%) preterm births occur annually, directly contributing to 75% of neonatal mortality and 50% of long-term neurological impairment in children. Moreover, it accounts for 35% and 10% of healthcare spending for infants and children, respectively. Many developing countries are unable to cope with the healthcare costs associated with managing neonates that are born preterm, resulting in higher and often unacceptable neonatal morbidity and mortality.
Unfortunately, the incidence of preterm labor has changed very little over the last 40 years and uncertainties still persist regarding the best strategies for its management. It has been widely recognised that its prevention and/or effective management will improve neonatal outcome and will have a profound impact on societal and long-term public healthcare costs. In this article we review the epidemiology and recent advances in prediction, prevention and management of preterm labor.
Overall incidence of preterm labor is reported to be 6-15% 1 and 4-50% of these occur spontaneously, whereas 25% occur following preterm pre-labor rupture of membranes (PPROM). Iatrogenic preterm labor due to obstetric intervention to avoid maternal or fetal compromise, accounts for about 25%.
Up to 75% of preterm labor occurs either spontaneously or following PPROM and many attempts have been made to develop methods that may help us to predict the onset of preterm labor so that measures could be taken to prevent its occurrence. These include –
A previous history of preterm labor is the strongest risk marker. It has been estimated that the incidence of preterm labor in subsequent pregnancies after one preterm birth rises to 14.3% and after two preterm births to 28% 2.
