Early-term delivery
Cognitive Scores
The children born at 37 weeks GA had lower mean cognitive scores than those born at 40 weeks (27 912 children; SMD, -0.13; 95% CI, -0.21 – -0.05; I2, 54%; moderate certainty evidence; Trim and Fill, -0.09, -0.18 – -0.01), as shown in Figure 2 a). There was no significant difference between children born at 38 and 40 weeks GA (33 004 children; SMD, -0.04; 95% CI, -0.08 – 0.002; I2, 42%; moderate certainty evidence; Trim and Fill, -0.04, -0.09 – 0.02) (Figure 2 a). The children born at early-term (37 and 38 weeks GA combined) had lower mean cognitive scores than full-term (39 to 41 weeks) born children (39 171 children, SMD, -0.14; 95% CI, -0.26 – -0.02; I2, 95%; low certainty evidence; no publication bias) (Figure 2 a). Due to the high heterogeneity, we conducted a subgroup analysis based on the age of follow-up. The mean differences tended to be smaller in older children (see Appendix S5).
Cognitive impairment
More cognitive impairment cases were found in children born at 37 weeks (71 597 children; OR, 1.23; 95% CI, 1.13 – 1.33; I2, 49%; moderate certainty evidence; Trim and Fill, 1.30, 1.20 – 1.42) and at 38 weeks (92 572 children; OR, 1.08; 95% CI, 1.03 – 1.12; I2, 0%; moderate certainty evidence; no publication bias) compared to those born at 40 weeks (Figure 2 b). Cognitive impairment was more common in early-term born children than full-term (939 397 children; OR, 1.19; 95% CI, 1.13 – 1.25; I2, 86%; low certainty evidence; Trim and Fill, 1.17, 1.11 – 1.23) (Figure 2 b). We also conducted a subgroup analysis based on age at follow-up in this synthesis, see Appendix S5. The results showed that the OR for cognitive impairment reduced with increasing age at follow-up, except for one study55.
Low academic performance
More low academic performance happened in those born at 37 weeks GA (576 869 children; OR, 1.17; 95% CI, 1.02 – 1.35; I2, 96%; moderate certainty evidence; Trim and Fill, 1.03, 0.91 – 1.17) and 38 weeks GA (614 005 children; OR, 1.10; 95% CI, 1.01 – 1.19; I2, 92%; moderate certainty evidence; Trim and Fill, 1.03, 0.95 – 1.13) compared to those born at 40 weeks (Figure 2 c). Low academic performance was more common in early-term born than full-term children (2 714 784 children; OR, 1.15; 95% CI, 1.09 – 1.21; I2, 96%; low certainty evidence; Trim and Fill, 1.05, 0.99 – 1.11) (Figure 2 c). The heterogeneity of the studies in these three data syntheses was high. We conducted subgroup analyses according to the outcome measurement scales, see Appendix S5.