Table 4

Number of events, crude event rates (per 1000), crude IRRs and adjusted HRs for the four outcomes according to the dose of valproic acid dispensed during pregnancy—main analysis and sensitivity analysis restricted to women considered to be treated for epilepsy

EventsCrude event ratesMain analysisWomen with epilepsy
IRRHR* (95% CI)IRRHR* (95% CI)HR† (95% CI)
Neurodevelopmental disorders<700 mg76.31.3 (0.6 to 2.8)1.3 (0.6 to 2.8)1.5 (0.7 to 3.4)1.6 (0.7 to 3.6)1.6 (0.7 to 3.6)
700–1500 mg2311.52.3 (1.4 to 3.8)2.1 (1.3 to 3.5)2.7 (1.6 to 4.6)2.5 (1.5 to 4.3)2.7 (1.6 to 4.6)
≥1500 mg2033.56.8 (4.1 to 11.5)7.0 (4.3 to 11.5)7.9 (4.5 to 13.8)8.6 (5.1 to 14.5)8.7 (5.2 to 14.6)
Pervasive developmental disorders<700 mg21.81.7 (0.4 to 7.6)2.2 (0.5 to 8.5)1.9 (0.4 to 9.3)2.9 (0.7 to 11.6)2.7 (0.7 to 11.4)
700–1500 mg73.43.3 (1.3 to 8.4)2.7 (1.0 to 7.1)3.7 (1.3 to 10.7)3.1 (1.1 to 9.0)3.0 (1.0 to 8.9)
≥1500 mg812.812.2 (4.9 to 30.4)14.7 (6.2 to 34.7)14.0 (5.1 to 38.5)17.0 (6.5 to 44.6)15.4 (5.7 to 41.1)
Mental retardation<700 mg54.43.1 (1.1 to 8.5)1.5 (0.4 to 5.9)3.4 (1.2 to 9.9)1.8 (0.4 to 7.0)1.6 (0.4 to 6.7)
700–1500 mg52.51.7 (0.6 to 4.7)1.8 (0.7 to 4.9)1.9 (0.6 to 5.5)1.9 (0.7 to 5.7)2.6 (1.0 to 6.7)
≥1500 mg57.95.5 (2.0 to 15.2)7.3 (3.0 to 17.7)6.0 (2.1 to 17.6)7.1 (2.7 to 18.7)8.4 (3.4 to 20.4)
Visits to a speech therapist<700 mg1311.60.8 (0.4 to 1.3)0.6 (0.3 to 1.0)0.7 (0.4 to 1.3)0.6 (0.3 to 1.0)0.5 (0.3 to 0.9)
700–1500 mg5427.31.8 (1.3 to 2.5)1.6 (1.2 to 2.1)1.7 (1.2 to 2.3)1.5 (1.1 to 2.0)1.5 (1.1 to 2.1)
≥1500 mg2643.42.9 (1.9 to 4.3)2.6 (1.7 to 4.0)2.7 (1.8 to 4.1)2.6 (1.7 to 4.0)2.7 (1.8 to 4.1)
  • *Adjusted for all covariates except hospitalisation for epilepsy during pregnancy.

  • †Adjusted for all covariates including hospitalisation for epilepsy during pregnancy.

  • CI, confidence interval; HR, hazard ratio; IRR, incidence rate ratio.