Table 13:
Risk of Pregnancy Loss
| Chromosomal Anomaly | Mean; Distribution (alpha; beta) | Sources |
|---|---|---|
| Spontaneous Pregnancy Loss Between 12 Weeks (First Trimester) and Term | ||
| Trisomy 21 | 43%; beta (30.2; 40.0) | Morris et al, 199985 |
| Trisomy 18 | 72%; beta (55.0; 21.4) | Morris et al, 200886 |
| Trisomy 13 | 49%; beta (9.2; 9.6) | Morris et al, 200886 |
| Spontaneous Pregnancy Loss Between 18 Weeks (Second Trimester) and Term | ||
| Trisomy 21 | 23%; calculated | Morris et al, 199985 |
| Trisomy 18 | 65%; calculated | Morris et al, 200886 |
| Trisomy 13 | 42%; calculated | Morris et al, 200886 |
| Spontaneous Pregnancy Loss Between 12 Weeks (First Trimester) and 18 Weeks (Second Trimester) | ||
| Trisomy 21 | 26%; calculated | Morris et al, 199985 |
| Trisomy 18 | 20%; calculated | Morris et al, 200886 |
| Trisomy 13 | 12%; calculated | Morris et al, 200886 |
| Spontaneous Pregnancy Loss Between Diagnostic Testing (CVS or Amniocentesis) and Term | ||
| Monosomy X (45,X) | 40%; beta (8; 12) | Iyer et al, 201295 |
| Triple X syndrome | 3%a; fixed | Estimate based on Tartaglia et al, 2010; Hook, 198389,96 |
| XXY syndrome (47,XXY) | 4%; fixed | Bojesen et al, 2003; Hook, 198396 |
| XYY syndrome | 3%a; fixed | Hook, 198396 |
| 22q11.2 deletion syndrome | 62%; fixed | Estimate based on Hook et al, 198396 |
| Voluntary Termination of Pregnancy for a Confirmed Affected Fetus | ||
| Trisomy 21 | 74.6%; beta (2,033; 691) | Natoli et al, 201297 |
| Trisomy 18 | 74.6%; beta (2,033; 691) | Estimate |
| Trisomy 13 | 74.6%; beta (2,033; 691) | Estimate |
| Sex chromosome aneuploidy | 68%; beta (115; 54) | Christian et al, 200098 |
| 22q11.2 deletion syndrome | 68%; beta (115; 54) | Estimate |
| Diagnostic-Procedure-Related Pregnancy Loss | ||
| Amniocentesis | 0.11%; fixed | Akolekar et al, 20156 |
| Chorionic villus sampling | 0.22%; fixed | Akolekar et al, 20156 |
| Background Risk of Spontaneous Pregnancy Loss for Unaffected Fetuses | ||
| From 12 weeks (first trimester) to term | 3%; fixed | Ammon et al, 2012; Wyatt et al, 200594,99 |
| From 18 weeks (second trimester) to term | 1%; fixed | Ammon et al, 2012; Wyatt et al, 200594,99 |
| From 12 weeks (first trimester) to 18 weeks (second trimester) | 2%; fixed | Ammon et al, 2012; Wyatt et al, 200594,99 |
a
We assumed that the risk of spontaneous pregnancy loss for affected fetuses was greater than or equal to that of the unaffected fetus: 3%.