Premature Birth and Long-Term Developmental Outcomes in Children

Introduction to Prematurity and Early Complications

Babies who are born "too soon" or "too small" are at risk for many complications (Allen, 2003). Babies born too soon are called premature, or preemies; they are born before the 36th week of gestation. Those who weigh less than 5½ pounds are considered "too small" and are referred to as dysmature. The implications for disabilities vary between these two groups.

In a premature infant, body systems and physical characteristics are often underdeveloped. In most cases, the more premature the infant, the less developed these systems are (Allen, 2003). There is less muscle tone; the respiratory system is not fully developed; the brain may not yet be ready to control breathing; and an immature nervous system may inhibit the feeding process. The baby may also experience jaundice (a yellowing of tissue because the liver is unable to regulate the secretion of bilirubin), hypoglycemia (too little glucose in the blood), and hypothermia (an inability to maintain body temperature due to a lack of insulating fatty tissue). Advanced medical procedures can manage these factors in many premature infants, but careful monitoring — typically in a neonatal intensive care unit (NICU) — is needed until the child's body systems mature enough to function independently.

According to Carter (1995): "Following discharge from the Neonatal Intensive Care Unit (NICU), children born very prematurely can be expected to differ from healthy full-term babies in many aspects of their development. Most notably, the development of most preterm babies follows expectations more closely when age is 'corrected' for prematurity rather than based on actual age. Even when compared with other children of their corrected age, however, most children born more than a few weeks early will have at least some additional developmental differences associated with prematurity during infancy. While developmental differences for most children born prematurely are benign and will eventually resolve, some of these differences can be associated with long-term problems. In some cases, long-term difficulties can be minimized by helping families and professionals to better understand the underlying conditions that influence the child's development."

In dysmature infants, the chances of respiratory distress are reduced, but the baby may still experience hypothermia, hypocalcemia (lack of calcium in the blood), and hypoglycemia (Allen, 2003). The incidence of developmental disabilities is higher in low birth weight babies. Dysmaturity is more likely in babies whose mothers had poor nutrition during pregnancy or were chronically ill; adolescent mothers are also at higher risk for low birth weight babies.

For infants who have experienced respiratory distress and required ventilation, many will develop an eye condition that could lead to severe visual impairment (Allen, 2003). Retinopathy of prematurity (ROP) occurs most often in premature infants born at 23–28 weeks gestation, or in those weighing less than 1,000 grams (approximately 2 pounds 3 ounces).

After the dangerous first weeks of a premature baby's life pass, the vast majority of preemies grow healthily and normally (Stanway, 1997). Most low birth weight babies catch up with their peers quickly. However, very low birth weight babies are likely to remain smaller than their peers for some years.

Advancements in medical science have led to a significant increase in the survival rate of premature infants, defined as those born at less than 37 weeks gestation and/or with a birth weight of less than 2,500 grams (Education Station, 2004). Some people incorrectly assume that, although premature infants may have a delay in "starting," they will eventually "catch up." It is widely believed that any differences in development will disappear by 2 to 3 years of age.

While some premature children do eventually catch up, others remain small throughout life. According to a study reported in 1996 of 249 eight-year-olds who had very low birth weight (Stanway, 1997):

The facts are that a significant number of premature children — up to 50 percent — have difficulties throughout the school years and have been found to need special education or additional resources, such as orthopedic or visual services (Education Station, 2004). Some research suggests a higher incidence of speech and language problems. Difficulties in understanding language, word finding, vocabulary, average length of response, sentence complexity, and giving and understanding definitions have all been reported. Additionally, children born prematurely have scored lower on tasks requiring sequencing, organization of visual information, visual-motor integration, and attention skills.

A premature baby's developmental skills — such as smiling, sitting, walking, and talking — are usually delayed by the number of weeks the baby was premature, and possibly longer if the neonatal course was difficult (Stanway, 1997). A recent study of eight-year-old children born before 32 weeks revealed the following:

The overwhelming majority — nine out of ten premature babies — grow up with no persistent health or developmental disability (Stanway, 1997). The more mature a baby is at birth, the lower the risk. For instance:

Regular assessments mean that, if a premature baby develops an ongoing problem, help or treatment can begin sooner rather than later (Stanway, 1997). Differences in IQ between children who had a low birth weight and those of normal birth weight are likely to be minimal on average. However, studies show that those with a very low birth weight have an average IQ approximately seven points lower than children of normal birth weight. One study demonstrated that the risk of serious learning difficulty in very low birth weight children was 7 to 11 times higher than for those of normal weight. Attention deficit disorder, tics, clumsiness (dyspraxia), and speech difficulty are also more common in children who had a low birth weight.

As far as cerebral palsy is concerned, the following statistics have been recorded (Stanway, 1997):

A study by Buck et al. (2000) assessed the impact of extreme prematurity on three global measures of school outcomes. Using a matched cohort design, exposed infants comprised all surviving singleton infants born under 28 weeks gestation at one regional neonatal intensive care hospital between 1983 and 1986. Unexposed infants comprised randomly selected full-term infants (greater than 37 weeks gestation) matched on date of birth, zip code, and health insurance. All children were drawn from a regional tertiary children's center serving the western New York population. Standardized telephone interviews elicited information on grade repetition, special education placement, and use of school-based services. Unconditional logistic regression was used to estimate odds ratios (OR) and corresponding 95% confidence intervals (CI) adjusted for potential confounders among children without major handicaps. Extreme prematurity was linked to a significant increase in risk of grade repetition, special education placement, and use of school-based services compared with children born at term, even after controlling for age, race, maternal education, foster care placement, and matching factors. These findings suggest that survivors of extreme prematurity are at risk of educational underachievement.

According to a recent study, premature babies may face educational problems when they reach school age (Martin, 2001). As many as one-third of babies born slightly prematurely will go on to have problems at school. Earlier studies examined the long-term emotional and behavioral consequences for babies born very prematurely (at 32 weeks or less). However, a 2001 paper published in Archives of Disease in Childhood revealed that children born only slightly early — between 32 and 35 weeks into the pregnancy — face "very significant risks" of having problems at school.

This group also faces a higher risk of developmental problems compared to children born at full term (Martin, 2001). Additional studies reveal that 10–20 percent of children born at full term performed below average, compared to one-third found in this study of slightly premature children.

Doctors surveyed parents and teachers of 117 children born prematurely in Oxfordshire in 1990, who made up between two and three percent of the babies born in that county that year (Martin, 2001). General practitioners were also asked to provide basic medical information.

Evidence of Preemies' Disadvantages

Charlotte Huddy at the John Radcliffe Infirmary in Oxford led the study, which examined the educational and behavioral problems experienced by the children at seven years of age (Martin, 2001). One-third were found to have problems with writing, mathematics, or fine motor skills such as drawing. One-quarter needed support from a non-teaching assistant, according to teachers. Four percent had special educational needs, and 3 percent attended a special school. One-third of the group were described as hyperactive by either a parent or a teacher, though only 8 percent were described as hyperactive by both.

Teachers were questioned about the children's educational abilities in speaking and listening, writing and composition, fine motor skills, mathematics, reading, and physical education, and were asked to rank these skills on a scale from one (good) to five (poor) (Martin, 2001). Children who scored either four or five in three or more skill areas, or who needed additional help at school, were considered to have poor school performance. Teachers also completed a questionnaire addressing behavioral problems.

According to Peter Hope, a consultant neonatologist at the John Radcliffe and co-author of the study (Martin, 2001): "Parents of some premature babies are quite relieved when they find out this might be associated with prematurity, rather than anything they might have done."

The study concluded (Martin, 2001): "Despite the methodological limitations of this study, it is clear that children of school age who were born at 32–35 weeks gestation have a very severe risk of educational difficulties. The increased risk of problems should be recognized in this very large group of babies as well as the survivors of extreme prematurity."

In 1999, Holsti, Grunau, and Whitfield completed a study at the University of British Columbia on impaired physical functioning that did not meet the criteria for cerebral palsy (Harrison, 2000a). This condition was referred to as Developmental Coordination Disorder (DCD). Of the 114 children in the study who were born between 1982 and 1987, 40 (35 percent) had CP and/or subnormal IQ (below 85) and/or sensorineural problems and were excluded. Of the remaining 74 "normal" children, 51 percent were classified as having DCD, defined as performing one standard deviation below the norm on tests of fine and gross motor skills.

Grunau, Whitfield, and McConnell published a study involving the same children, reporting that difficulties with written work are eight times more common among "normal" preemies than among full-term controls (Harrison, 2000a). These problems, observed at age 8, were predicted by low scores at age 4½ in numerical problem solving, pencil copying, and visual perception. The study presented sample essays written by the preemies and full-term children; the differences in handwriting, continuity of thought, and expression were significant.

According to the authors: "This study highlights continuities in visual-motor perceptual functioning and learning problems. Story writing is a complex activity requiring multifaceted problem-solving in addition to pencil skills."

In 1996, Kamaya, Moddemann, and Casiro completed a study for the University of Manitoba in Winnipeg, examining 48 "non-handicapped" very low birth weight preemies and finding that they had intellectual, academic, visual-spatial, and attention span weaknesses compared to full-term controls (Harrison, 2000a). Behavior and social competence were rated lower by both parents and teachers, with significant differences found in somatic complaints, anxiety/depression, social problems, attention problems, and aggressive behavior.

Twenty-one percent of the preemies had scores in the abnormal clinical range on total behavior problems; 19 percent were in the abnormal range on somatic complaints; 17 percent were in the abnormal clinical range for attention; and 15 percent were in the abnormal clinical range for aggression (Harrison, 2000a).

A separate study also demonstrated that preemies tend to have more problems in school and in childhood socializing than babies carried to full term (Recer, 2002). This study, by psychology researchers at Syracuse University, showed that significantly more children born prematurely had behavioral, learning, and thinking problems compared to children born at full term.

The study, conducted by Lawrence Lewandowski and Jeremie Barlow, compared the development of 118 babies born prematurely with that of 119 babies delivered after full-term gestation (Recer, 2002). The results were based on tests that began at birth and continued at intervals until age 10.

According to Barlow, 39 percent of the premature babies had below-normal IQs of 85 or less, while only 13 percent of the full-term infants had IQs this low (Recer, 2002). The international average for IQs of 85 or less is 16 percent.

Based on data from questionnaires completed by teachers and parents, researchers also found that premature children had more social problems (Recer, 2002). "More of them did poorly on measures of social skills," said Barlow. "There was more peer conflict and they tended to have fewer friends and less social success."

In a study measuring academic skills, 41 of the premature children (35 percent) scored poorly on an academic screening test, while only 10 of the full-term children (about 8 percent) scored poorly (Recer, 2002). Twenty-eight of the 118 premature children were classified as learning disabled, compared with only 11 of the 119 full-term children.

"The results indicated that preterm children were more likely to have clinically significant scores — indicating impairment — on more than one measure and in more than one area," according to the study (Recer, 2002).

According to Lewandowski, earlier studies found that children born prematurely were up to four times less likely to graduate from high school (Recer, 2002). The later study showed that social and academic deficits begin very early and continue until at least age 10. He expressed hope that these children could be followed through high school to determine whether they improve with maturity.

Regardless, the study suggests strongly that parents of premature babies need to make special efforts to enrich the social and intellectual development of their children (Recer, 2002). Lewandowski said such parents should seek professional guidance to learn special parenting skills that could potentially help these children. Approaches such as infant massage, physical contact, bright and interesting visual objects, and pleasant, varied sounds all provide stimulation that may help premature infants develop stronger intellectual and social skills for the school years.

"Children who are at increased risk for developmental problems include those born very prematurely or at very low birth weight," says Sheena Carter, Ph.D., a developmental psychologist at Emory School of Medicine in Atlanta (Morrison, 2002). "While most prematurely born children develop beyond any problems associated with their early experiences, frequently there are developmental issues that need to be addressed as early as possible in order to prevent further complications."

According to Carter, periodic re-evaluation is important during infancy and early childhood, as most developmental difficulties emerge slowly over time (Morrison, 2002). "Some of the variables that influence the potential for catch-up growth include size for gestational age at birth, genetic growth potential, nutritional factors, and neurological injury. It is not possible to accurately predict the later growth of an individual child."

Cognitive, Motor, and Behavioral Deficits in Research

Jennifer Pinto-Martin, a nursing professor at the University of Pennsylvania, has been involved in the Neonatal Brain Hemorrhage Study, the largest regional study of premature babies (Morrison, 2002). These babies have been studied for 14 years. "While many babies born prematurely do very well in terms of growth and development, many have physical and psychological problems that emerge as the child grows up," says Pinto-Martin. "We have found that poor school performance and the need for special education is not always recognized when the child first enters school, but may be more apparent by third or fourth grade."

With high-risk children, in-depth screening and evaluation is essential (Morrison, 2002). The tests routinely used with the general population are not adequate to gather accurate information about high-risk developmental problems. Follow-up for high-risk infants ideally involves periodic screening for sensory impairment, developmental delays, and any other condition for which a child may be at increased risk.

Many premature babies suffer from chronic medical and developmental problems — such as chronic lung disease, respiratory distress, visual impairment, feeding difficulties, and cerebral palsy — and three recent studies suggest these setbacks do not disappear over time (Williams, 2000). Researchers revealed that about half of preemies suffer from some form of disability, with one-quarter suffering severely, and that preemies tend to have more problems in school and in childhood socializing. One United Kingdom study followed preemies from birth to age 5; a Syracuse University study followed children to age 10; and a third study, published in the American Sociological Review, tracked children to age 19.

The researchers found that preemies have significantly more behavioral, learning, and thinking problems than children born full term, and that babies born weighing less than 5½ pounds are almost four times more likely not to graduate from high school by age 19 than their normal birth weight peers (Williams, 2000).

The chronic medical and developmental problems suffered by preemies can make learning and developing socialization skills difficult, according to Joan McCollom, a former physical therapist and special education teacher with 31 years of experience in the San Diego Unified School District (Williams, 2000). "You can't expect them to keep up academically year by year. They can learn what another child can learn, but it's going to take them more time. If you can't get out and play with the other kids, then socialization skills are more difficult."

Children born approximately three months prematurely are 3 to 4 times more likely to struggle in school than children born full term (Wrape, 2000). Compared with full-term children, preemie children were more likely to repeat a grade (33 percent versus 18 percent), receive special education (20 percent versus 5 percent), and require extra help with reading, spelling, math, handwriting, speech and language, and occupational or physical therapy (16 percent versus 6 percent).

A variety of studies have estimated that as many as 40 to 50 percent of children born prematurely will have some form of learning disability (Wrape, 2000). One study was carried out in which none of the premature children suffered from major preemie-related health problems such as cerebral palsy, chromosomal abnormalities, hearing loss, or intellectual disability. According to one of the study's authors: "In a sense, the children in our study represented a kind of 'sleeper phenomenon' — none had noticeable disabilities. There's no way to pick up on some of these developmental problems in the first two years of life, so many of these children showed no outward signs of disabilities."

Brain scans of preemie children show that crucial areas of the brain are much smaller than those of full-term children (Wrape, 2000). One Yale study was the first to relate brain abnormalities in preemies to cognitive outcome and perinatal risk factors. The differences in brain volume were significant across all regions, with reductions ranging from 11 to 35 percent. While not all preemies showed brain abnormalities, high-risk preemies were most affected, and the magnitude of abnormalities was directly proportional to risk status and strongly associated with IQ scores at age 8.

According to Dr. Laura Ment: "Premature birth at less than 1,000 grams birth weight is a major cause of developmental disability (Wrape, 2000). Infants in this birth weight range represent almost 1 percent of all births in our country, and the survival rate is well over 80 percent, but the incidence of handicap is high. By age 8, over 5 percent are in special education or receiving extensive resource room help. One fifth have already repeated a grade of school. The study shows that when brains develop prematurely outside of the womb, they are vulnerable to developmental disturbances."

Children born extremely prematurely, considered high risk, experience significant learning disabilities that continue into their teenage years (Wrape, 2000). A Canadian study followed 150 premature babies into their teens. Nearly half were receiving special education assistance, compared with just 10 percent of a control group of full-term children matched for gender, age, and social class. A quarter of preemies had repeated a grade, compared with just 6 percent of controls. Fewer than half of the smallest preemies scored in the normal range on most intelligence and achievement tests.

An Israeli study measured the emotional and behavioral development of prematurely born children, demonstrating that premature children had higher levels of anxiety, depression, and aggression than full-term children, and that they had a lower self-concept (Wrape, 2000). Premature children also had more disturbances at home and at school. This study revealed that the smaller the birth weight, the less emotionally adjusted the child tended to be.

One study compared four birth weight groups to examine the effect of birth weight on classroom behavior among children entering elementary school. According to Wrape (2000): "Extremely low birth weight children had lower attention and language skills, overall social competence, scholastic competence, and athletic ability than all other birth weight groups as measured by classroom teachers, even when controlling for neonatal stay, child's gender and ethnicity, and maternal education. All low birth weight children had lower attention and language skills and scholastic competence and higher daydreaming and hyperactivity scores than normal birth weight children. The classroom behavior of low birth weight children was rated by teachers as poor, even for children who had not failed a grade. Low birth weight children who are on grade level may still be at risk for problems."

In 1998, Goyen, Lui, and Woods studied 83 "normal" preemies and found that 71 percent had below-average fine motor skills (Harrison, 2000a). Twenty-three percent of these children were considered impaired or seriously impaired. A similar study of 64 "normal" preemies by Luoma, Herrgard, and Martikainen found that they achieved lower scores in visuospatial and sensorimotor functions compared to full-term controls. According to the authors, they had most difficulty with the direction of drawn lines and with integrating two or more forms, as well as with three-dimensional constructions and the visual perception of rotated shapes or slopes of lines (Harrison, 2000a).

According to Harrison (2000a): "The studies by Skranes and others indicate that most VLBW preemies have suffered white matter damage [PVL]. Recent research shows that white matter loss can negatively affect gray matter development. Gray matter makes up the frontal lobe, and the frontal lobe handles much of what is referred to as 'executive function' — such abilities as planning, sequencing, and inhibition of impulsive behavior."

A 1999 study from Mater Children's Hospital in Australia (Harvey, O'Callaghan, and Mohay) tested 30 extremely low birth weight preemies at age 4 to 5 and compared their abilities with 30 full-term children of the same age (Harrison, 2000a). The preemies scored significantly lower than their peers on all executive function tasks.

A study from Queen's University in Belfast, Northern Ireland (Sykes, Hall, Bill et al., 1997) examined a cohort of 243 prematurely born very low birth weight children at age 7–8 (Harrison, 2000a). Teachers reported that both male and female preemie children expressed more behavioral and school adjustment problems than controls. Environmental factors such as high social class played no role in ameliorating these problems. The authors speculated that the problem behaviors "reflect a failure in self-regulatory (executive, or frontal lobe) functions."

Conclusion and Implications for Practice

Researchers and doctors now understand the limitations of trying to use information available during infancy and early childhood to predict future development (Carter, 1995). The most sophisticated imaging technology is unable to predict later motor functioning for an individual infant with absolute accuracy, and the specific impairments related to early brain injury vary across children with similar injuries. Therefore, stakeholders must maintain a focus on the current impact of neurological injury rather than attempting to determine whether particular symptoms will or will not resolve over time. In this light, it is possible to address relevant needs as they arise by working to enhance each child's strengths and to minimize the impact of any impairments as they emerge.