The relationship between placental and other perinatal risk factors for neurologic impairment in very low birth weight children

Placental abnormalities reflect antenatal disease processes that may interact with other perinatal risk factors to affect long-term outcome. We performed a nested case control analysis of placental and clinical risk factors associated with neurologic impairment (NI) at 20-mo corrected age (60 cases and 59 controls) using data collected in a prospective study of very low birth weight (less than 1500 g) infants born between 1983 and 1991. In a preliminary analysis we explored the relationship between clinical infection and histologic chorioamnionitis (CA). Only histologic CA with a fetal vascular response correlated with either clinical CA or early onset neonatal sepsis. We then assessed the relative contribution of the nine risk factors (four placental and five clinical) associated with NI at the univariate level by multiple logistic regression. Three risk factors were independent predictors of NI: severe cranial ultrasound abnormalities (odds ratio 13.6, 95% confidence intervals 4.5-66.7), multiple placental lesions (odds ratio 13.2, 95% confidence intervals 1.3-137.0), and oxygen dependence at 36 wk (odds ratio 4.2, 95% confidence intervals 1.2-14.6). Finally, a series of logistic regressions was conducted with the dependent variable changing as we moved back along the causal chain to explore the relationships between risk factors operating at different stages. This analysis suggested that antenatal variables that were not independent predictors of NI by multiple logistic regression exerted their effects through the following intermediate pathways: fetal grade 3 histologic CA via chorionic vessel thrombi, clinical CA via grade 3 villous edema, and grade 3 villous edema via severe cranial ultrasound abnormalities.

Placental lesions associated with neurologic impairment and cerebral palsy in very low-birth-weight infants

OBJECTIVE

Systematic placental examination has the potential to shed light on poorly understood antenatal processes that may increase the risk of neurologic impairment and cerebral palsy.

DESIGN

Using data from a retrospective case-control study, we analyzed placentas from 60 inborn, singleton, very low-birth-weight (<1.5 kg) infants delivered between 1983 and 1991 who had subsequent neurologic impairment at 20 months corrected age (42 with cerebral palsy and 18 with other neurologic abnormalities) and 59 control infants of comparable gestational age, birth weight, sex, and race. Three a priori hypotheses based on previous studies were that neurologic impairment would be increased with fetal vascular lesions with or without coexisting chorioamnionitis, decreased with chronic maternal vascular underperfusion, and increased when multiple placental abnormalities were seen in the same case.

RESULTS AND CONCLUSIONS

We found 2 types of fetal placental vascular lesions to be associated with neurologic impairment, namely, recent nonocclusive thrombi of chorionic plate vessels (P < .04) and severe villous edema (P < .01). Chorionic plate thrombi were seen only with chorioamnionitis and accounted for the increased risk of neurologic impairment seen with chorioamnionitis. Maternal vascular lesions showed a biphasic relation to neurologic impairment in the subgroup of patients without chorioamnionitis. Mild lesions were increased in controls (inadequate vascular remodeling, P=.03, and accelerated maturation, P=.004). A more severe lesion, multiple villous infarcts, although not reaching significance, was increased in the neurologically impaired cases. Finally, in a test of 9 selected placental lesions, cases with cerebral palsy were more likely to have 2 or more lesions (P < .0001) and were less likely to have no lesions (P < .04) than control infants.

Perinatal correlates of cerebral palsy and other neurologic impairment among very low birth weight children

BACKGROUND AND OBJECTIVE

The etiology of neurologic impairments among very low birth weight (VLBW, <1.5 kg) children is poorly understood. We sought to investigate the perinatal predictors of major neurologic impairment, including cerebral palsy, among VLBW children.

METHODS

Antenatal, intrapartum, and neonatal events and therapies were compared between 72 singleton inborn VLBW children born between 1983 to 1991 who had neurologic impairment at 20 months corrected age (including 50 with cerebral palsy and 22 with other neurologic impairments) and 72 neurologically normal VLBW children matched by birth weight, gestational age, race, and sex via a retrospective case-control method. Multiple logistic regression was conducted, entering only those variables found to be significant at the bivariate level.

RESULTS

There were no significant differences in the rates of pregnancy-induced hypertension, maternal tocolytic use including magnesium, or antenatal steroid therapy. Higher rates of clinical chorioamnionitis were found among the mothers of the neurologically impaired children as compared with controls (31% vs 11%), but not among the subgroup of mothers of children with cerebral palsy (22% vs 12%). Significant differences in neonatal factors among the total neurologically-impaired group (n = 72) versus controls included oxygen dependence at 36 weeks (31% vs 15%), septicemia (53% vs 31%), severe cranial ultrasound abnormality (50% vs 17%), and hypothyroxinemia (43% vs 25%). In the subgroup with cerebral palsy (n = 50), significant differences included days on the ventilator (23 vs 14 days), septicemia (54% vs 33%), and severe cranial ultrasound abnormality (52% vs 12%). Multivariate analysis controlling for birth weight, gestational age, race, sex, and the birth period (before 1990 versus 1990 and after) revealed direct and independent effects of clinical chorioamnionitis [odds ratio (OR), 3. 79; confidence interval (CI), 1.34-10.78], severe cranial ultrasound abnormality (OR, 9.97; CI, 3.84-25.87), and septicemia (OR, 2.46; CI, 1.10-5.52) on total neurologic impairment. Consideration of the 50 cases with cerebral palsy revealed direct and independent effects of severe cranial ultrasound abnormality only (OR, 15.01; CI, 4.34-51. 93).

CONCLUSIONS

Both antenatal and neonatal risk factors contribute to the development of severe neurologic impairment, including cerebral palsy among VLBW children. Because prevention of chorioamnionitis may not be feasible in the near future, attempts to decrease neonatal risk factors such as severe cranial ultrasound abnormalities and sepsis may be most feasible at this time.

Neonatal auditory brainstem response failure of very low birth weight infants: 8-year outcome

Fifty-six very low birth weight infants (less than 1.5 kg) were followed until 8 y of age to see if predischarge auditory brainstem response (ABR) results were predictive of neurobehavioral development. The results suggest that early ABR may predict subsequent performance on measures of intelligence quotient, language, and reading. Unilateral ABR abnormalities did not appear predictive, but bilateral abnormalities did. Analysis of a variety of neonatal risk factors in conjunction with early ABR and hearing loss with respect to educational outcome was also undertaken.

Effect of very low birth weight and subnormal head size on cognitive abilities at school age

BACKGROUND

We tested the hypothesis that very-low-birth-weight (less than 1.5 kg) infants with perinatal growth failure whose head size is not normal by eight months of age (corrected for prematurity) have significantly poorer growth and neurocognitive abilities at school age than very-low-birth-weight children with a normal head size at eight months. We also hypothesized that these differences would persist even after control for major neurologic impairment and perinatal and sociodemographic risk factors.

METHODS

We have followed a cohort of very-low-birth-weight children since their birth during the period 1977 to 1979. At eight to nine years of age 249 children were evaluated with a neurologic examination and tests of intelligence; receptive and expressive language skills; speech, reading, mathematics, and spelling aptitude; visual and fine motor abilities; and behavior. Ages were corrected for premature birth.

RESULTS

Among these 249 very-low-birth-weight children, head size was subnormal (less than the mean -2 SD for age) at birth in 30 (12 percent), at term in 57 (23 percent), and at eight months in 33 (13 percent). As compared with the 216 children with normal head sizes, the 33 children with subnormal head sizes at the age of eight months had significantly lower mean birth weights (1.1 vs. 1.2 kg) and higher neonatal risk scores (71 vs. 53) and at the age of eight years had a higher incidence of neurologic impairment (21 percent vs. 8 percent) and lower IQ scores (mean verbal, 84 vs. 98). Even among the children without neurologic abnormalities, a subnormal head size at eight months of age was predictive of poorer verbal and performance IQ scores at eight years of age; lower scores for receptive language, speech, reading, mathematics, and spelling; and a higher incidence of hyperactivity. In multiple regression analyses to control for socioeconomic and neonatal risk factors, intrauterine growth failure, birth weight, and neurologic impairment, a subnormal head size at eight months of age had an independently adverse effect on IQ and on scores for receptive language, speech, reading, and spelling.

CONCLUSIONS

In very-low-birth-weight infants, perinatal growth failure, as evidenced by a subnormal head circumference at eight months of age, is associated with poor cognitive function, academic achievement, and behavior at eight years of age.