Medical history taking in adults should include questions about preterm birth

Clinicians increasingly encounter adult patients who were born preterm (after fewer than 37 completed weeks of gestation). Advances in neonatal care that were introduced in the 1970s and 1980s, including high frequency ventilation, surfactant therapy, and antenatal corticosteroids, have enabled unprecedented numbers of such infants to survive. The first generation to benefit from those advances are now young adults. And a growing body of evidence for long term health consequences has contributed to a developmental model for early life origins of chronic disease.

Variations in fetal and postnatal nutrition are hypothesised to permanently alter gene expression, resulting in so called programming for the onset of chronic disease in later life.1 This involves a complex interplay of hormonal and immunological mechanisms and is commonly associated with preterm birth. Epidemiological studies have shown that the long term health consequences are wide ranging, including increased risks of diabetes, cardiovascular disease, respiratory disease, and neurological and psychiatric disorders into adulthood.2 3 4 5 These health effects also carry increased long term risks of mortality.

In a large national cohort study in Sweden, my colleagues and I found that among all people who survived to young adulthood, those born preterm had about a 40% increased risk of dying during young adulthood (aged 18 to 36 years) compared with people who had been born at full term (adjusted hazard ratio for all cause mortality 1.4; 95% confidence interval 1.2 to 1.6).6 7 This risk was greater for earlier gestational ages and was about double among young adults who were born extremely preterm (less than 28 weeks).6 Furthermore, these findings were not limited to preterm gestational ages but extended to early term births (37 to 38 completed weeks of gestation), which were associated with an approximate 15% increase in mortality in young adulthood compared with people born at later term (adjusted 95% CI 1.1 to 1.2).7

We identified multiple causes of this early mortality, including an approximate two-fold increased risk of death from diabetes among young adults who were born either preterm or at early term, and increased cardiovascular and respiratory mortality. These findings were similar among men and women, and were not explained by sociodemographic differences or congenital anomalies that are more common with preterm birth. Although longer follow-up will be needed into later adulthood, other studies of diabetes and cardiovascular disease have indicated that the risks associated with preterm birth persist in older ages. The continued high prevalence of preterm birth (nearly 12% in the United States) and increasing numbers who are surviving into adulthood mean that the long term health effects will have a growing clinical and public health impact.

Clinical standards of care do not adequately reflect these substantial long term health effects. Preterm birth is not widely treated in clinical practice as an important long term risk factor for chronic disease and mortality in adults. Relatively few physicians ascertain birth history in patients beyond childhood. A UK survey of 123 respiratory specialists found that only a small minority (less than 25%, mostly hospital pediatricians) asked “most respiratory patients” about birth history, such as preterm birth, birth weight, or perinatal complications, and a large proportion did not ask patients at all.8

In primary care, ascertainment of birth history among adult patients is not well studied but is likely to be even less common. But the relative mortality risks associated with preterm birth are at least those of other health factors commonly ascertained by medical history. The risk of all cause mortality6 7 associated with preterm birth (about 40% in young adulthood) is higher than estimates associated with poor nutrition (relative risk 1.1 to 1.2), heavy alcohol use (1.2 to 1.3), or physical inactivity (1.2 to 1.4),9 10 nearly as high as those associated with current smoking (1.4 to 1.8)9 10; and likely higher than those associated with most family history information.11

Family history of disease and a history of preterm birth differ from lifestyle factors because they are not modifiable. However, better awareness of associated risks can help motivate healthy behaviour change among people born preterm. Aggressive reduction of other modifiable risk factors is even more imperative for the prevention of health problems, including diabetes, cardiovascular disease, and respiratory disease, for which preterm birth is an important risk factor.

Gestational age at birth is routinely recorded in countries that use birth registries and in some hospital records. Other healthcare systems where it does not currently exist should develop systematic tracking of this information. Without such records, the reliability of history of preterm birth reported by patients or their families is not well established and needs further evaluation. Some studies have reported that maternal recall of gestational age (or birth weight) is sufficiently accurate for clinical use,12 but self reported history among adult patients has not been well studied. The accuracy of patient reported history is likely to improve, however, with increasing public and media awareness of the long term relevance of preterm birth.

Although preterm birth is a long term risk factor for multiple chronic diseases, its predictive significance for specific outcomes beyond the effects of other known risk factors is unclear. As with many other known risk factors for disease, additional research will be needed to elucidate its predictive significance for specific clinical profiles and outcomes. Nonetheless, it provides important context for understanding a patient’s health.

The ascertainment of preterm birth history among adults is supported by substantial evidence for increased long term health risks. This is especially relevant among younger adults who currently have a higher proportion of preterm survivors but will become increasingly relevant among older adults as these birth cohorts age. The medical history for adults should encompass, when available, birth history including gestational age at birth (or preterm birth: yes/no), birth weight, and perinatal complications.

Medical education regarding history taking should also be updated to incorporate this perspective. Ascertaining a history of preterm birth would enable the patient and physician to be better aware of the potential health risks throughout the life course; to consider more intensive screening for such risks, including cardiovascular and metabolic disorders; and motivate behaviour changes to reduce other common risk factors.