A premature birth is defined as the delivery of a baby before 37 full weeks of pregnancy are completed. Due to significant advancements in neonatal intensive care, survival rates for infants born very and extremely preterm have dramatically improved since the 1980s. This success has created a growing population of adults whose physical health profiles are marked by their earliest weeks of life. Prematurity interrupts organ development during a period of rapid growth, leading to lifelong changes in the body’s structure and function. Understanding these persistent physical characteristics is important for adult healthcare providers managing potential chronic health conditions effectively.
Long-Term Impacts on Stature and Body Composition
One of the most noticeable physical characteristics persisting into adulthood is a reduction in overall size. Individuals born very preterm frequently achieve a shorter final adult height compared to those born at term. This difference is proportional to the degree of prematurity and persists even after a period of rapid “catch-up” growth in early childhood.
Adults born very low birth weight often exhibit a body composition profile distinct from their term-born peers, characterized by a lower lean body mass. This reduction in muscle and bone mass can contribute to lower muscular fitness and potential functional limitations. Studies indicate an altered distribution of fat, with some preterm-born adults showing a tendency toward higher central or truncal adiposity.
This difference in fat storage, particularly visceral fat accumulation, is a manifestation of early life programming. Bone health is also affected, with lower bone mineral density often observed in adults who were born preterm. This suboptimal bone mass suggests a vulnerability to conditions like osteopenia and an increased risk of future fractures.
Persistent Respiratory and Cardiovascular Vulnerabilities
The heart and lungs are two organ systems that bear a lasting imprint from being born prematurely, often necessitating long-term monitoring. The lungs, highly immature at preterm birth, may never fully achieve the functional capacity of a term-born individual. Many adults show evidence of reduced pulmonary function, often displaying both restrictive and obstructive patterns consistent with chronic lung disease.
Even without a history of severe neonatal lung disease, such as bronchopulmonary dysplasia, survivors have an increased susceptibility to asthma and chronic obstructive pulmonary disease-like symptoms later in life. This reduced lung capacity, marked by a deficit in predicted forced expiratory volume in the first second (FEV1), can limit exercise tolerance and physical fitness.
The cardiovascular system likewise exhibits measurable differences, with adult survivors facing higher rates of systemic hypertension. Young adults born preterm have systolic blood pressure readings that are, on average, 3.8 mm Hg higher than those born at term. This elevated pressure is linked to subtle structural changes in the heart, including smaller ventricular volumes and thicker heart walls, making the heart less efficient.
The blood vessels themselves can also be affected, showing increased vascular stiffness and greater peripheral resistance. These mechanical and structural differences suggest a reduced cardiac reserve—the heart’s ability to cope with physical or physiological stress. These factors place adults born preterm at a higher risk for cardiovascular disease and heart failure later in life.
Alterations in Metabolic and Endocrine Function
The early interruption of development in the womb programs the metabolic system in ways that become apparent in adulthood. Prematurity, particularly when combined with low birth weight, is theorized to induce a “thrifty phenotype,” where the body is programmed to conserve energy and store fat efficiently in anticipation of nutrient scarcity. This programming impacts the body’s ability to regulate energy, leading to significant endocrine and metabolic changes.
Adults born preterm are at an elevated risk of developing features of the metabolic syndrome, including insulin resistance and Type 2 diabetes. Studies show that preterm-born individuals are 2.5 to 4 times more likely to meet the criteria for metabolic syndrome compared to their full-term counterparts. Insulin resistance, where the body’s cells do not respond effectively to insulin, is a precursor to Type 2 diabetes and is detectable in young adulthood.
Specific markers of dysregulation include higher levels of glycated hemoglobin and increased C-peptide, which are indicators of impaired glucose control. Adverse lipid profiles, such as lower levels of high-density lipoprotein (HDL) cholesterol, are frequently observed. Endocrine disruption extends beyond metabolism, with some studies indicating an increased chance of hypothyroidism in adulthood.
Sensory and Neuromotor Outcomes
Despite the absence of severe neurological disabilities, many adults born preterm exhibit persistent, subtle physical challenges related to sensory processing and motor control. These enduring issues stem from the early vulnerability of the developing brain and nervous system. The most common sensory impairments involve vision and hearing.
Visual problems, such as high rates of myopia (nearsightedness), are common, and some individuals may have residual effects from retinopathy of prematurity (ROP), a condition affecting the retina. Hearing loss is also a recognized outcome, sometimes requiring the use of hearing aids in adulthood.
In the realm of physical movement, subtle neuromotor deficits are often present, even in the absence of conditions like Cerebral Palsy. These can manifest as difficulties with fine motor skills, gait, and balance, often categorized as developmental coordination disorder or minor neurological dysfunction. Specific deficits include issues with sensory integration and motor confusion, which reflect challenges in the brain’s ability to coordinate sensory information with physical action.