Table 1.
Endogenous congenital disorders included in MGDb-ZA, estimated baseline live birth prevalence, characteristics, proportion of disorder group and total, South Africa 2012
| Congenital disorder group | Prevalence characteristics | Source of estimated birth prevalence | Affected per1000 live births (SA) | % of total in MGDb-ZA | % of disorder group |
|---|---|---|---|---|---|
| Rare single-gene disorders | |||||
| Baseline rare single-gene disorders | Constant | (Stevenson 1959, Trimble and Doughty 1974, Carter 1977, Baird et al. 1988) | 4.27 | 16.3 | 91.0 |
| Consanguinity-associated | Population-specifica | (Bundey and Alam 1993, Bittles and Neel 1994, Blencowe et al. 2018b) | 0.17 | 0.6 | 3.6 |
| Common single-gene disorders | |||||
| Oculocutaneous Albinism | Population-specific | (Kromberg and Jenkins 1982) | 0.25 | 1.0 | 5.3 |
| Total single-gene disorders | 4.69 | 17.9 | 100 | ||
| Chromosomal disorders | |||||
| Down syndrome | Population-specificb | (Moorthie et al. 2018a, b, c) | 1.73 | 6.6 | 45.8 |
| Other trisomiesc | Population-specificd | (Moorthie et al. 2018a, b, c) | 0.33 | 1.3 | 8.7 |
| Rare chromosomal | Constant | (Wellesley et al. 2012) | 0.67 | 2.6 | 17.7 |
| Turner syndrome | Constant | (EUROCAT 2015) | 0.18 | 0.7 | 4.8 |
| Klinefelter syndrome | Constant | (Visootsak and Graham 2006, Morris et al. 2008) | 0.87 | 3.3 | 23.0 |
| Total chromosomal disorders | 3.78 | 14.4 | 100 | ||
| Isolated malformationse | |||||
| Congenital heart diseasef | Constant | (EUROCAT 2009, Tennant et al. 2010, Wren et al. 2012) | 3.30 | 12.6 | 18.7 |
| Neural tube defects | Population-specific | (Sayed et al. 2008) | 0.90 | 3.4 | 5.1 |
| Oral facial clefts | Population-specific | (Mossey and Little 2002, EUROCAT 2015) | 0.24 | 0.9 | 1.4 |
| Very severe other malformationsg | Constant | (EUROCAT 2015, Moorthie et al. 2018a, b, c) | 7.00 | 26.8 | 39.6 |
| Less severe other malformationsh | Constant | (EUROCAT 2015, Moorthie et al. 2018a, b, c) | 5.15 | 19.7 | 29.1 |
| Three additional conditionsi | Population-specific | (Modell and Modell 1992) | 1.10 | 4.2 | 6.2 |
| Total isolated malformations | 17.69 | 67.6 | 100 | ||
| Total disorders included in MGDb ZA | 26.19 | 100 | 100 | ||
aEquation: Consanguinity associated/1,000 = Population F x 100 x 6.5 (Blencowe et al. 2018b).
bEquation: (0.834 + (% mothers 35plus x 0.067)) x 1.053 (Moorthie et al. 2018a).
cEdwards and Patau syndromes (Trisomy 18 and 13) are grouped together due to similar outcomes.
dEquation: equivalent to 41% of Down syndrome /1,000 (Moorthie et al. 2018a).
eIsolated malformations i.e. not associated with a chromosomal disorder or genetic syndrome or a malformation in another system group.
fCongenital heart defects that present before 20 years of age and would cause premature death or disability in the absence of intervention (Moorthie et al. 2018c).
gPotentially fatal other malformations in absence of care: CNS not NTD, eye, ear, face and neck, respiratory, digestive, abdominal wall defects, urinary system, multiple malformations.
hPotentially non-fatal malformations in the absence of care: genital and limb.
iThree potentially lethal isolated malformations not included in most congenital anomaly registries but that are preventable or curable (thyroid aplasia/hypoplasia, prematurity-related persistent patent ductus arteriosus, pyloric stenosis) are combined as a single category due to relatively weak evidence for local birth prevalence