The contribution of birth defects to preterm birth and low birth weight.
OBJECTIVE
To assess the impact of birth defects on preterm birth and low birth weight.


METHODS
Data from a large, prospective multi-center trial, the First and Second Trimester Evaluation of Risk (FASTER) Trial, were examined. All live births at more than 24 weeks of gestation with data on outcome and confounders were divided into two comparison groups: 1) those with a chromosomal or structural abnormality (birth defect) and 2) those with no abnormality detected in chromosomes or anatomy. Propensity scores were used to balance the groups, account for confounding, and reduce the bias of a large number of potential confounding factors in the assessment of the impact of a birth defect on outcome. Multiple logistic regression analysis was applied.


RESULTS
A singleton liveborn infant with a birth defect was 2.7 times more likely to be delivered preterm before 37 weeks of gestation (95% confidence interval [CI] 2.3-3.2), 7.0 times more likely to be delivered preterm before 34 weeks (95% CI 5.5-8.9), and 11.5 times more likely to be delivered very preterm before 32 weeks (95% CI 8.7-15.2). A singleton liveborn with a birth defect was 3.6 times more likely to have low birth weight at less than 2,500 g (95% CI 3.0-4.3) and 11.3 times more likely to be very low birth weight at less than 1,500 g (95% CI 8.5-15.1).


CONCLUSIONS
Birth defects are associated with preterm birth and low birth weight after controlling for multiple confounding factors, including shared risk factors and pregnancy complications, using propensity scoring adjustment in multivariable regression analysis. The independent effects of risk factors on perinatal outcomes such as preterm birth and low birth weight, usually complicated by numerous confounding factors, may benefit from the application of this methodology, which can be used to minimize bias and account for confounding. Furthermore, this suggests that clinical and public health interventions aimed at preventing birth defects may have added benefits in preventing preterm birth and low birth weight.


METHODS
II.
Dolan
Siobhan M
SM
Albert Einstein College of Medicine/Montefiore Medical Center, 1300 Morris Park Avenue, Bronx, NY 10461, USA. sdolan@aecom.ae.yu
Gross
Susan J
SJ
Merkatz
Irwin R
IR
Faber
Vincent
V
Sullivan
Lisa M
LM
Malone
Fergal D
FD
Porter
T Flint
TF
Nyberg
David A
DA
Comstock
Christine H
CH
Hankins
Gary D V
GD
Eddleman
Keith
K
Dugoff
Lorraine
L
Craigo
Sabrina D
SD
Timor-Tritsch
Ilan
I
Carr
Stephen R
SR
Wolfe
Honor M
HM
Bianchi
Diana W
DW
D'Alton
Mary E
ME
D000328:Adult; D025063:Chromosome Disorders; D015331:Cohort Studies; D000013:Congenital Abnormalities; D005260:Female; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D016017:Odds Ratio; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology*; D011446:Prospective Studies; D012307:Risk Factors