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. 2017 Oct 17;2:101. [Version 1] doi: 10.12688/wellcomeopenres.12783.1

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

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