Birth at 28-31 weeks gestation is defined as very preterm and accounts for less than 1% of all deliveries and about 10% of preterm births. Immediate survival is expected with a significant proportion of short to long-term morbidity. Below 28 weeks is regarded as extremely preterm (less than 5% of all preterm births) where early neonatal mortality is high with up to 50% of severe handicaps occuring among survivors born below 26 weeks. Recent reports described survival rates among extremely low gestational ages (24-25 weeks) according to obstetrical variables at admission.
Gestational age at birth is now recognised as a reference standard related to the outcome and prognosis of the preterm infant, together with birthweight. Mild prematurity refers to 32-36 weeks, which could be further subdivided into mild (32-33 weeks) and moderate (34-36 weeks) preterm birth. Mild prematurity accounts for the great majority of all preterm births. Although immediate neonatal outcomes are usually reported to be encouraging, this group contributed significantly to an excessive infant mortality in the post-neonatal period (up to one year of age) from asphyxia related conditions, infection and suddent infant death syndrome.
Being born before 37 weeks gestational age or before 259 days, is defined as preterm birth according to the World Health Organisation. In this definition, the lower limit is not specified. Preterm birth could be qualified according to birthweight with large variations depending on the studied populations or to gestational ages strata. Preterm birth could also be categorised by its clinical presentations: medically induced, preterm premature rupture of membranes and spontaneous preterm labour leading to preterm delivery. Several aetiologies and/or risk factors have been reported for each of the three categories although none completely explain all preterm births. Recent investigations, more directed to defined plausible biological pathways, may reconcile the apparent heterogeneity of preterm birth
Preterm birth is stratified into:
- Mild preterm (32-35 weeks)
- Very preterm (28-31 weeks)
- Extremely preterm (<28 weeks)
The majority of multiple pregnancies are delivered preterm. Although medical indications relate more to feto-maternal conditions, preterm premature rupture of membranes to infections and idiopathic preterm birth to lifesyle, these risk factors are identified in any category, emphasing that preterm birth has a multifactorial origin. Still, several incidences of preterm birth are not completely explained with a plausible cause for preterm premature rupture of membranes or spontaneous preterm labour suggesting that other causes have yet to be identified. In addition, preterm birth is associated with unrecognized severe congenital anomalies.
Three main conditions explain preterm birth:
- Medically indicated (iatrogenic) preterm birth
- Preterm premature rupture of membranes
- Spontaneous (idiopathic) preterm birth
What happens if my labor does not stop?
If your labor does not stop and its look like you will give birth to early, you and the baby usually will be cared for by a team of health care professionals. The team may include a neonatologist, a doctor who specializes in treating problems in newborns. The care your baby needs depends on how early he or she is born. High-level neonatal intensive care units (NICUs) provide this specialized care for preterm infants.