Preterm infants – Definition, classifications and associated risk factors

Preterm birth is the leading cause of morbidity and mortality in children¹, with the risk of mortality being inherently linked to gestational age². Complications associated with preterm births represent the largest direct cause of neonatal deaths, estimated at approximately 27%³. 

Preterm birth can be divided into two subtypes: 

1. Spontaneous preterm birth: spontaneous onset of labour <37 weeks gestation or following prelabour premature rupture of membranes, referred to as PPROM³. 
2. Initiated preterm birth: induction of labour or elective caesarean section (C-section) <37 weeks gestation due to either obstetric or foetal distress, or both³.   

There are several maternal risk factors that are associated with preterm birth. Maternal history of preterm birth significantly increases the risk of subsequent preterm births. Any underlying maternal chronic medical conditions such as diabetes, anaemia, thyroid disease, hypertension and asthma will predispose the mother to a preterm birth, increasing the risk of preeclampsia for example. It is therefore crucial to identify the presence of such conditions prior to conception, providing appropriate care throughout pregnancy to control the risk^3,4. Other factors include age at pregnancy, multiple pregnancy, lifestyle (e.g. smoking, alcohol, drug misuse), nutritional status (e.g. underweight, overweight, nutrient deficiencies), induction of C-section birth, physical and psychological well-being and infection^3,4. 

Certain foetal conditions which may result in a medically indicated preterm birth include preeclampsia, placental abruption, uterine rupture, foetal distress and foetal growth restrictions. 

Advances in neonatal care and medicine have significantly improved the survival rates of these preterm infants, ensuring that they are given the best possible chance of survival. Each member of the MDT plays a vital role in the growth and development of these infants. Being aware of the relevant risk factors of preterm births and the challenges that these infants are faced with, can result in the enhancement of the overall care of this vulnerable cohort.