The number of births, years of follow-up and expected events in each simulation
| THIN-CPRD database | HES database | |
| CS births | 206 615 | 2 070 500 |
| Postclamping antibiotics | 111 508 | 1 115 670 |
| Preincision antibiotics | 95 107 | 954 830 |
| VD births | 570 774 | 5 973 100 |
| Total births | 777 389 | 8 043 600 |
| CS person years of follow-up | 792 265 | 8 661 832 |
| Postclamping antibiotics | 501 401 | 5 524 890 |
| Preincision antibiotics | 290 864 | 3 136 942 |
| VD person years of follow-up | 2 215 405 | 25 339 526 |
| Total person years of follow-up | 3 007 670 | 34 001 358 |
| New events in children born by CS | 7173 | 15 333 |
| Postclamping antibiotics | 5324 | 10 454 |
| Preincision antibiotics | 1849 | 4880 |
| New events in children born by VD | 20 378 | 44 906 |
| Total events | 27 551 | 60 240 |
| Average event rate per 1000 person years | 9.2 | 1.8 |
CPRD, Clinical Practice Research Datalink; CS, caesarean section; HES, Hospital Episode Statistics; THIN, The Health Improvement Network; VD, vaginal delivery.