August 21, 2001

Risk for birth defects among premature infants: a population-based study.

Rasmussen SA, Moore CA, Paulozzi LJ, Rhodenhiser EP. J Pediatr 2001; 138: 668-73

Rasmussen et al. collected a population-based cohort study of 264,392 preterm and term neonates. The purpose of the study was to develop incidence data regarding congenital malformations in full term vs preterm infants.[1] They found that preterm infants were more that two times more likely to have congential birth defects than full term infants and that this risk was inversely related to gestational age. This is an important paper for anesthesiologists if simply to provide a red flag. Already we know that all organ systems in the preterm infant are immature. The resulting reduced glomerular filtration and immature hepatic enzyme systems as well as altered protein binding (less albumen) in the preterm infant reduces the infant’s ability to excrete medications, (e.g., thiopental). They may also require larger initial loading doses (e.g., succinylcholine) because of the larger extracellular fluid volume compared with older patients. Their immature blood-brain barrier may make them more vulnerable to the adverse effects of sedating medications. Respiratory system immaturity both in terms of surfactant production and their respiratory center (apnea) present additional problems for the anesthesiologist. Cardiovascular immaturity makes them more likely to have cardiovascular depression with inhalation anesthetics and unable to increase cardiac output except primarily through increases in heart rate (atropine in their friend). This paper now shows us that we as anesthesiologists must have a heightened awareness of the potential for congenital malformations that would further complicate the patient’s life as well as ours.

1. Rasmussen SA, Moore CA, Paulozzi LJ, Rhodenhiser EP: Risk for birth defects among premature infants: a population-based study. J Pediatr 2001; 138: 668-73

AUTHORS:
Rasmussen SA, Moore CA, Paulozzi LJ, Rhodenhiser EP.

SOURCE:
J Pediatr 2001; 138: 668-73

OBJECTIVE: To investigate the relationship between prematurity and birth defects. STUDY DESIGN: In a population-based cohort study, infants with birth defects were ascertained through the Metropolitan Atlanta Congenital Defects Program, a surveillance system with active methods of ascertainment. Gestational age data were obtained from birth certificates of liveborn, singleton infants with and without birth defects born in the 5-county metropolitan Atlanta area.

RESULTS: Among 264,392 infants with known gestational ages born between 1989 and 1995, 7738 were identified as having birth defects (2.93%). Premature infants (<37 weeks' gestation) were more than two times as likely to have birth defects than term infants (37-41 weeks) (risk ratio = 2.43; 95% CI 2.30-2.56). This relationship was evident for several categories of birth defects. The rate of birth defects varied by gestational age categories, with the highest risk in the 29- to 32-week gestational age category (risk ratio = 3.37). CONCLUSIONS: The risk for birth defects is increased in premature infants. Awareness of this relationship is important for clinicians caring for premature infants. The morbidity and mortality associated with a particular defect may be significantly altered by the presence prematurity. Further study of this association may provide insight into the etiology of these relatively common problems.