Extremely low gestational age neonates are more likely than term infants to develop cognitive impairment. Few studies have addressed antenatal risk factors of this condition. We identified antenatal antecedents of cognitive impairment determined by the Mental Development Index (MDI) portion of the Bayley Scales of Infant Development, Second Edition (BSID-II), at 24 months corrected age.


We studied a multicenter cohort of 921 infants born before 28 weeks of gestation during 2002 to 2004 and assessed their placentas for histologic characteristics and microorganisms. The mother was interviewed and her medical record was reviewed. At 24 months adjusted age, children were assessed with BSID-II. Multinomial logistic models were used to estimate odds ratios.


A total of 103 infants (11%) had an MDI <55, and 99 infants (11%) had an MDI between 55 and 69. No associations were identified between organisms recovered from the placenta and developmental delay. Factors most strongly associated with MDI <55 were thrombosis of fetal vessels (OR 3.1; 95% confidence interval [CI] 1.2, 7.7), maternal BMI >30 (OR 2.0; 95% CI 1.1, 3.5), maternal education ≤12 years (OR 3.4; 95% CI 1.9, 6.2), nonwhite race (OR 2.2; 95% CI 1.3, 3.8), birth weight z score < −2 (OR 2.8; 95% CI 1.1, 6.9), and male gender (OR 2.7; 95% CI 1.6, 4.5).


Antenatal factors, including thrombosis of fetal vessels in the placenta, severe fetal growth restriction, and maternal obesity, convey information about the risk of cognitive impairment among extremely premature newborns.

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