Primary outcome
Our findings suggest no causal effect of IVF conception on developmental vulnerability, with 13.6% of IVF-conceived children predicted to be developmentally vulnerable (<10th percentile in 2 or more domains of the 5 AEDC domains) compared with 13.9% of spontaneously conceived children. The adjusted RD was at −0.3%, indicating that 0.3% fewer children who were conceived by IVF were developmentally vulnerable compared with those conceived spontaneously. However, the 95% CI (−3.7% to 3.1%), indicates this result is indistinguishable from zero. Similarly, the adjusted relative risk showed no detectable difference in risk of developmental vulnerability, where IVF-conceived children were 3.0% less likely to be developmentally vulnerable than spontaneously conceived children (RR 0.97, 95% CI: 0.77 to 1.25) (