Table 2. Results of individual studies comparing cognitive outcomes of children born within term (37-42 weeks gestation), ordered by participant age at cognitive testing.
| Study (n) | Cognitive test
and overall scores |
Age at
testing (years) |
Main findings | Effect size (95%CI)/significance
level |
Risk of
bias a |
|||
|---|---|---|---|---|---|---|---|---|
| Scores | ||||||||
| Espel
et al. 2014
18
(n = 232) |
BSID-II (Bayley
scores of infant development) Range 50-150 MDI and PDI € |
1 | GA
b
37-38 39-40 41 |
MDI mean ± SD
c
92±NA e 95±NA 96±NA |
PDI mean±SD
d
92.5±NA 97±NA 106±NA |
Gestational age as a continuous
variable Adj MDI f b = 2.0 (0.45-3.51), p <0.05 Adj PDI g b = 3.9 (1.52 - 6.05), p <0.01 |
Moderate | |
| Rose
et al. 2013
19
(n = 1562) |
Original BSID
(Bayley scores of infant development) MDI and PDI |
1 | GA (n)
37 (45) 38 (260) 39 (469) 40 (604) 41 (184) |
MDI mean ± SD
102.6±11.4 103.4±12.3 103.3±12.9 105.1±11.5 105.4±12.2 |
PDI mean (SD)
94.4±14.9 94.4±14.6 96.6±15.4 98.5±15.1 97.6±14.8 |
Gestational age as a continuous
variable Adj MDI h b = 0.8 (0.2-1.4), p = 0.025 Adj PDI i b = 1.4 (0.6-2.1), p = 0.036 |
Moderate | |
| Gyamfi-Bannerman
et al. 2014 21 (n = 20,093) |
Stanford-Binet IQ
Full scale intelligence Quotient (IQ) Range 40-160 |
4 | GA (n)
37 (1290) 38 (2361) 39 (4040) 40 (4816) 41 (3782) 42 (1953) |
Mean IQ Scores (95%CI)
95.9 (93.6 - 95.3) 97.6 (95.2 - 96.5) 98.6 (97.1 - 98.1) 99.8 (98.1 - 99.0) 99.8 (99.3 - 100.4) 98.1 (99.0 - 100.5) |
Test of linear trend
P <0.001 |
High | ||
| Yang
et al. 2009
20
(n = 13,824) |
WASI (Wechsler
Abbreviated Scale of Intelligence) Full scale intelligence quotient (IQ) Range 40-160 |
6.5 | GA (n)
37 (469 38 (2100) 39 (11074) 42 (171) 43 (10) |
IQ scores
NA NA NA NA NA |
Unadj mean diff
(95%CI) -2.6 (-3.7 - -1.4) 0.6 (-1.1- -0.01) REF k -1.4 (-3.5 - 0.6) -5.8 (-14 - -2.5) |
Adj
j mean diff
(95%CI) -1.7 (-2.7 - -0.7) -0.4 (-1.1 - 0.2) REF -0.4 (-2.5 - 1.7) -5.9 (-15 - 3.3) |
Moderate | |
bGA = Gestational age
cMDI = Mental Developmental Index, SD = standard deviation
dPDI = Psychomotor Developmental Index
eNA = not available
f,g β coefficients represent the actual change in score with each additional week of term, Adj = adjusted for factors ethnicity, parity, maternal age, obstetric risk, birth weight percentile
h,iMeans difference coefficients represent the actual change in score with each additional week of term, Adj = adjusted for factors fetal sex, birth weight centile, socio-economic status
kREF = Reference category
jAdjusted for cluster, birth weight, sex, maternal age, maternal height, parental education, and parental occupation