The treatment of small preterm babies has developed tremendously during the recent decades. Most famous developments include introduction of neonatal ventilators in the 1970s, glucocorticoids given to the mother to enhance maturation of the fetus from the 1970s and pulmonary surfactant to treat the immaturity of lungs from the 1980s. Other advances include improved nutrition, general developments in intensive care and family-centered care.
The prognosis of small preterm infants has improved accordingly. While even in high-resource settings XX% of infants born preterm with a birth weight less than 1500 g survived to be discharged home, in the 1980s the figure was 70-80% and today close to 90%.
With improving survival, neonatologists have become interested on the long-term outcomes of babies born preterm. Much of this research has focused on those born smallest or most immature, for example very preterm (below 32 weeks), extremely preterm (below 28 weeks), very low birth weight (below 1500 grams) or extremely low birth weight (below 1000 g).
A general conclusion from these studies is that most adults born as small preterms live healthy lives that they are satisfied with. However, when they are compared with those born at term as a group, a number of differences become visible.
Adults born preterm gain less scores in cognitive functioning tests. Usually this difference amounts to approximately to 0.5 standard deviations, a moderate difference, although it varies according to the study population and to the specific test used.
Studies assessing personality characteristics suggest a specific “preterm personality” characterized by risk aversion, shyness and cautiousness in social relationships. Accordingly, adults born preterm start family later and in population studies are less likely to have children than those born at term. Some studies have also suggested higher average levels of conscientiousness. Conscientiousness is strongly associated with healthy lifestyle and good health. In line with this, studies have found lower rates of alcohol use among adults born preterm. Of course, these differences are differences between groups; all types of individuals exist among those born preterm and those born at term.
Many studies have also shown higher levels of cardiovascular risk factors such as higher blood pressure, and impaired glucose regulation. Those born preterm also are more likely to develop type 2 diabetes as adults. Interestingly, adults born preterm report much lower rates of physical activity than their counterparts born at term. If this holds true in future studies, increasing health-enhancing physical activity would be a simple way to promote good health in children and adults born preterm.
It is not yet well known how these characteristics and risk factors should be interpreted in practice. For the first, we do not know to what extent they are due to the cause underlying preterm birth and to what extent conditions during neonatal intensive care after birth. Neither do we know much about how different neonatal diseases and treatments affect the outcome, and what types of family characteristics or childhood events protect from or increase the risk of these adverse outcomes. These relatively complicated questions are difficult to address in individual studies. They are, however, easier to study when data from several studies can be combined together. This is an important rationale for the APIC collaboration.