Table 4 Expected events in various situations of 800,000 pregnant women in one year (see an example of decision tree for model in Fig. 2)
From: Fetal Down syndrome screening models for developing countries; Part II: Cost-benefit analysis
Situations | No. DS live births | No. of spon-taneous abortion | No. of intention termina-tion | No. of abortion due to amniocenteses | No. of amniocen-teses and chromosome studies | |
|---|---|---|---|---|---|---|
Down + ve | Down -ve | |||||
1. No screening | 1152 | 475 | – | – | – | – |
2. Maternal age alone | 899 | 491 | 705 | 2 | 428 | 86,158 |
3. Second trimester screen (STS) alone | 367 | 280 | 947 | 4 | 325 | 65,794 |
4. Independent screen (I-S) | 333 | 329 | 876 | 4 | 265 | 53,827 |
 First trimester screen (FTS) | 226 | 247 | 600 | 3 | 136 | 34,615 |
 STS | 107 | 82 | 277 | 1 | 78 | 19,212 |
5. C-S plus STS | 318 | 296 | 841 | 5 | 178 | 36,592 |
 C-S | 211 | 214 | 565 | 3 | 67 | 17,380 |
 STS | 107 | 82 | 277 | 1 | 76 | 19,212 |
6. Maternal age with NIPS | 905 | 489 | 302 | 2 | 8 | 2178 |
7. STS alone with NIPS | 395 | 284 | 633 | 4 | 6 | 2093 |
8. Independent screen (I-S) with NIPS | 350 | 330 | 618 | 4 | 5 | 1911 |
 FTS with NIPS | 234 | 247 | 433 | 3 | 3 | 1300 |
 STS with NIPS | 115 | 83 | 185 | 1 | 2 | 611 |
9. C-S plus STS with NIPS | 354 | 323 | 619 | 4 | 3 | 1560 |
 C-S + NIPS | 239 | 240 | 434 | 3 | 2 | 949 |
 STS + NIPS | 115 | 83 | 185 | 1 | 1 | 611 |
10. Universal NIPS | 165 | 473 | 1051 | 7 | 73 | 16,089 |