You are a pediatrician expecting to see an infant who was born at 26 weeks' gestation tomorrow for her first outpatient clinic visit at 4 months after birth. You know the family well because you care for their older child who was born at 35 weeks' gestation and is now a healthy 3-year-old girl. This infant had a prolonged stay in the neonatal intensive care unit but required relatively minimal respiratory support during her first 3 weeks of life. The neonatologist told you that the infant did extremely well, experiencing none of the complications that often occur in extremely preterm infants. He also informs you that he warned the family, “Your baby is at risk for long-term neurocognitive and motor complications related to being born so prematurely. Although some babies born this prematurely grow up to lead normal lives, many have minor disabilities, and there is a nontrivial chance that your baby could develop moderate to severe disabilities.” You have 5 other children in your pediatric practice born at less than 27 weeks of gestation; all of them have major neurodevelopmental problems. On the basis of your professional experience, you wonder if the neonatologist has presented the family with an overly optimistic outlook. You decide to check out the evidence for yourself.
You use your clinic's free Internet connection to access MEDLINE at the National Library of Medicine website via PubMed. To find the appropriate search terms for your population of interest, you first type “premature” in the Medical Subject Headings database and find that there is a term called “Infant, Extremely Premature” defined as a human infant born before 28 weeks' gestation. You select it and click on the related link for Clinical Queries. Under Clinical Study Categories, you choose the search filter “Prognosis” and limit the scope to “Narrow.” This retrieves 31 clinical studies and 5 potential reviews. You first look for a systematic review but do not find one that is relevant for evaluating outcomes across multiple extremely premature infant cohorts. However, the second primary study in the search results seems promising: Neurodevelopmental Outcome of Extremely Preterm Infants at 2.5 Years After Active Perinatal Care in Sweden.1 This study reports the cognitive, language, and motor development of a prospective cohort of a consecutive sample of extremely preterm infants born before 27 weeks' gestation in Sweden between 2004 and 2007.1
Why and How We Measure Prognosis
Clinicians help patients in 3 broad ways: diagnosing or ruling out medical and health-related problems, administering treatment that does more good than harm, and giving them an indication of what the future is likely to hold. Clinicians require studies of prognosis—those examining the possible outcomes of a disease and the probability with which they can be expected to occur—to achieve the second and third goals.