Table 1

Characteristics of extremely preterm (EP) participants and term-born controls by age of assessment

VariablesWhole cohortAge 2.5 years*Age 6 yearsAge 11 yearsAge 19 years
EP (n=315)EP (n=283)EP (n=241)Control (n=160)EP (n=219)Control (n=153)EP (n=129)Control (n=65)
At birthEDD
Age (years)Mean (range)2.5 (2.3–3.3)6.3 (5.2–7.3)6.1 (5.1–7.2)10.9 (10.1–12.1)10.9 (9.8–12.3)19.3 (18.4–20.5)19.2 (18.1–20.3)
Male sex% (n)49 (155)49 (155)48 (135)51 (122)44 (71)46 (101)42 (64)47 (61)38 (25)
Gestational ageMean (SD)24.9 (0.7)24.9 (0.7)24.9 (0.7)24.9 (0.7)24.9 (0.7)24.9 (0.8)
 ≤23 weeks% (n)9 (29)9 (29)9 (26)10 (24)11 (23)11 (15)
 24 weeks% (n)32 (100)32 (100)32 (90)30 (73)32 (70)29 (37)
 25 weeks% (n)59 (186)59 (186)59 (167)60 (144)57 (126)60 (77)
Neonatal brain injury% (n/N)23 (71/314)23 (71/314)22 (63/283)22 (54/241)22 (49/218)17 (22/128)
Growth parameters
Height (cm)Mean
(95% CI)
88.6
(88.1 to 89.1)
(n=258)
112.7
(111.9 to 113.5)
(n=237)
116.2
(115.2 to 117.2)
(n=159)
139.7
(138.7 to 140.6)
(n=218)
144.5
(143.3 to 145.8)
(n=153)
163.7
(162.0 to 165.3)
(n=129)
167.7
(165.6 to 169.7)
(n=65)
Difference in means(95% CI)−3.5 (−4.8 to −2.3)−4.9 (−6.4 to −3.3)−4.0 (−6.8 to −1.3)
Height z-scoreMean
(95% CI)
−0.70
(−0.84 to −0.55)
(n=258)
−0.95
(−1.09 to −0.81)
(n=237)
−0.00
(−0.17 to 0.17)
(n=159)
−0.55
(−0.69 to −0.41)
(n=218)
0.15
(−0.01 to 0.32)
(n=153)
−0.98
(−1.19 to −0.78)
(n=129)
−0.18
(−0.42 to 0.06)
(n=65)
Difference in means(95% CI)−0.95 (−1.16 to −0.73)−0.71 (−0.92 to −0.50)−0.81 (−1.14 to −0.47)
Weight (kg)Mean
(95% CI)
0.75 (0.73 to 0.76)
(n=315)
2.57 (2.51 to 2.62)
(n=306)
11.9 (11.7 to 12.1)
(n=271)
18.8 (18.3 to 19.3)
(n=241)
21.6 (21.0 to 22.3)
(n=159)
34.1 (33.0 to 35.2)
(n=217)
38.4 (36.8 to 40.0)
(n=152)
62.8 (60.4 to 65.2)
(n=128)
69.6 (65.2 to 74.1)
(n=65)
Difference in means(95% CI)−2.8 (−3.6 to −2.0)−4.3 (−6.1 to −2.4)−6.8 (−11.4 to −2.3)
Weight z-scoreMean
(95% CI)
−0.18
(−0.26 to −0.09)
(n=312)
−1.69
(−1.81 to −1.57)
(n=299)
−1.19
(−1.35 to −1.03)
(n=271)
−1.18
(−1.35 to −1.01)
(n=241)
0.07
(−0.12 to 0.25)
(n=159)
−0.42
(−0.59 to −0.25)
(n=217)
0.21
(0.02 to 0.39)
(n=152)
−0.25
(−0.51 to −0.00)
(n=128)
0.54
(0.18 to 0.89)
(n=65)
Difference in means(95% CI)−1.25 (−1.51 to −0.99)−0.62 (−0.88 to −0.37)−0.79 (−1.22 to −0.36)
BMI (kg/m2)Mean
(95% CI)
15.1 (14.9 to 15.3)
(n=253)
14.6 (14.4 to 14.8)
(n=237)
15.9 (15.6 to 16.2)
(n=158)
17.3 (16.9 to 17.7)
(n=217)
18.2 (17.6 to 18.7)
(n=152)
23.3 (22.6 to 24.1)
(n=128)
24.7 (23.3 to 26.1)
(n=65)
Difference in means(95% CI)−1.3 (−1.7 to −1.0)−0.9 (−1.5 to −0.2)−1.3 (−2.8 to 0.1)
BMI z-scoreMean
(95% CI)
−1.00 (−1.17 to −0.83)
(n=253)
−0.87 (−1.03 to −0.70)
(n=237)
0.11 (−0.07 to 0.29)
(n=158)
−0.22 (−0.40 to −0.03)
(n=217)
0.17 (−0.03 to 0.37)
(n=152)
0.32 (0.08 to 0.56)
(n=128)
0.69 (0.36 to 1.02)
(n=65)
Difference in means(95% CI)−0.98 (−1.23 to −0.73)−0.39 (−0.66 to −0.11)−0.37 (−0.78 to 0.04)
Head circumference (cm)Mean
(95% CI)
23.3
(23.1 to 23.5)
(n=209)
33.3
(33.1 to 33.6)
(n=293)
48.3
(48.1 to 48.6)
(n=278)
50.6
(50.3 to 50.8)
(n=239)
52.2
(52.0 to 52.4)
(n=160)
52.5
(52.3 to 52.8)
(n=217)
54.3
(54.1 to 54.5)
(n=152)
55.0
(54.7 to 55.4)
(n=125)
56.6
(56.1 to 57.0)
(n=63)
Difference in means(95% CI)−1.6 (−2.0 to −1.3)−1.8 (−2.1 to −1.4)−1.5 (−2.1 to −0.9)
Head circumference z-scoreMean
(95% CI)
−0.24
(−0.42 to −0.06)
(n=207)
−0.88
(−1.06 to −0.70)
(n=287)
−1.56
(−1.74 to −1.39)
(n=278)
−1.63
(−1.79 to −1.46)
(n=239)
−0.33
(−0.49 to −0.17)
(n=160)
−1.27
(−1.44 to −1.10)
(n=217)
−0.01
(−0.17 to 0.14)
(n=152)
−0.84
(−1.07 to −0.61)
(n=125)
0.29
(0.02 to 0.55)
(n=63)
Difference in means(95% CI)−1.30 (−1.54 to −1.06)−1.26 (−1.50 to −1.02)−1.13 (−1.50 to −0.75)
  • *Growth measures corrected for prematurity at 2.5 years.

  • BMI, body mass index; EDD, expected date of delivery.