1. Background
1.1. The paradox of modern obstetrics
1.2. Other apparently contradictory phenomena in the perinatology
2. Discussion
2.1 Problems with traditional models
2.1.1. Time scales and anchors
2.1.2. Status of gestational age: determinant versus survival time
2.2. The fetuses at risk approach
2.2.1. Incidence of birth, labour induction, pregnancy complications
Gestational age | Stillbirths | Neonatal deaths | Live births | SGA live births | Rates (Conventional) | Fetuses at risk† | Rates (Fetuses at risk) | |||
SGA (%) | Perinatal mortality per 1,000 | Births per 1,000 | R-SGA per 1,000 | Perinatal mortality per 1,000 | ||||||
34 | 329 | 175 | 10661 | 1011 | 9.5 | 45.9 | 1583286 | 6.9 | 0.6 | 0.32 |
35 | 318 | 172 | 18128 | 1822 | 10.1 | 26.6 | 1572296 | 11.7 | 1.2 | 0.31 |
36 | 439 | 249 | 41962 | 4226 | 10.1 | 16.2 | 1553850 | 27.3 | 2.7 | 0.44 |
37 | 451 | 269 | 87566 | 9104 | 10.4 | 8.2 | 1511449 | 58.2 | 6.1 | 0.48 |
38 | 552 | 364 | 232039 | 22163 | 9.6 | 3.9 | 1423432 | 163.4 | 15.6 | 0.64 |
39 | 522 | 359 | 356922 | 35792 | 10.1 | 2.5 | 1190841 | 300.2 | 30.2 | 0.74 |
40 | 601 | 464 | 536302 | 54709 | 10.2 | 2.0 | 833397 | 644.2 | 65.9 | 1.28 |
41 | 304 | 219 | 245665 | 24104 | 9.8 | 2.1 | 296494 | 829.6 | 81.7 | 1.76 |
≥ 42 | 92 | 77 | 50433 | 5250 | 10.5 | 3.3 | 50525 | 1000.0 | 104.8 | 3.34 |
Total‡ | 8694 | 5562 | 1614531 | 160429 | 10.0 | 8.8 | 1623225 | 1000.0 | 100.0 | 8.70 |
Gestational age | Stillbirths | Neonatal deaths | Live births | SGA live births | Rates (Conventional) | Fetuses at risk† | Rates (Fetuses at risk) | |||
SGA (%) | Perinatal mortality per 1,000 | Births per 1,000 | R-SGA per 1,000 | Perinatal mortality per 1,000 | ||||||
34 | 42 | 23 | 2513 | 447 | 17.9 | 25.4 | 29170 | 87.6 | 15.5 | 1.99 |
35 | 28 | 14 | 3302 | 740 | 22.5 | 12.6 | 26615 | 125.1 | 28.0 | 1.39 |
36 | 28 | 23 | 5372 | 1491 | 27.8 | 9.4 | 23285 | 231.9 | 64.5 | 1.85 |
37 | 29 | 15 | 6835 | 2249 | 33.0 | 6.4 | 17885 | 383.8 | 126.7 | 2.18 |
38 | 30 | 11 | 6720 | 2695 | 40.2 | 6.1 | 11021 | 612.5 | 246.5 | 3.45 |
39 | 15 | 7 | 2843 | 1291 | 45.5 | 7.7 | 4271 | 669.2 | 304.8 | 5.15 |
40 | 11 | 2 | 1246 | 641 | 51.5 | 10.3 | 1413 | 889.6 | 458.2 | 9.20 |
41 | 1 | 0 | 129 | 71 | 55.5 | 7.7 | 156 | 833.3 | 461.0 | 6.41 |
≥ 42 | 0 | 0 | 26 | 18 | 69.2 | 0.0 | 26 | 1000.0 | 692.3 | 0.00 |
Total‡ | 703 | 869 | 34944 | 10325 | 29.9 | 44.1 | 35647 | 1000.0 | 298.8 | 44.1 |
2.2.2. The incidence of growth restriction
2.2.3. The incidence of perinatal death
2.2.4. Reconciling diverse perinatal conundrums
2.3. An epidemiologic framework for medically indicated early delivery
2.3.1. Incidence of medically indicated early delivery, birth, revealed SGA, and death
2.3.2. Number needed to treat
2.3.3. Number needed to treat under different scenarios
2.3.4. Problems with the NNT calculation
2.3.5. Marginal NNT calculation
Population | Labor induction/cesarean deliveries per 1,000 fetuses | Perinatal deaths*/1,000 fetuses | Number needed to treat (marginal) | ||||
1995–96 | 1999–00 | Change† | 1995–96 | 1999–00 | Change | ||
Singletons ≥ 28 weeks, all | 339.4 | 384.5 | 45.1 | 3.95 | 3.64 | 0.31‡ | 145 |
≥ 28 weeks, no medical risk factors | 294.6 | 337.7 | 43.0 | 2.98 | 2.68 | 0.29‡ | 146 |
≥ 28 weeks, with hypertension | 662.4 | 697.6 | 35.2 | 6.96 | 6.76 | 0.20 | 180 |
≥ 28 weeks, with diabetes | 532.4 | 578.4 | 46.0 | 6.67 | 6.49 | 0.18 | 257 |
≥ 28 weeks, with hyp. and diabetes | 744.6 | 779.3 | 34.7 | 8.83 | 9.96 | -1.13 | -31 |
Twins ≥ 28 weeks, all | 636.5 | 685.3 | 48.8 | 12.13 | 10.63 | 1.50‡ | 32 |
Singletons ≥ 34 weeks, all | 338.3 | 383.2 | 44.8 | 2.66 | 2.42 | 0.24‡ | 188 |
≥ 34 weeks, no medical risk factors | 294.5 | 337.5 | 42.0 | 2.09 | 1.86 | 0.23‡ | 181 |
≥ 34 weeks, with hypertension | 654.1 | 689.5 | 35.1 | 3.91 | 3.87 | 0.04 | 927 |
≥ 34 weeks, with diabetes | 533.3 | 579.8 | 45.7 | 5.25 | 5.14 | 0.11 | 403 |
≥ 34 weeks, with hyp. and diabetes | 740.9 | 776.6 | 35.0 | 6.86 | 7.29 | -0.43 | -81 |
Twins ≥ 34 weeks, all | 634.8 | 685.9 | 48.7 | 6.68 | 6.16 | 0.53 | 92 |