Table 1.
Demographic and related characteristics of mothers and probands
| Race of mother | Number | Percent |
| Caucasian | 237 | 87.5 |
| African-American | 33 | 12.2 |
| Asian/Pacific Islander | 1 | 0.4 |
| Age of mother | Mean years | |
| At proband's birth | 25.2 | |
| At time of survey | 43.5 | |
| Pregnancy outcome | Number (1) | Percent |
| Live birth | 701 | 87.7 |
| Spontaneous abortion | 95 | 11.9 |
| Stillbirth | 3 | .4 |
| History of spontaneous abortion | Number | Percent |
| No | 205 | 75.6 |
| Yes | 66 | 24.4 |
| Pregnancy distribution | Range | Mean |
| All pregnancies | 1 to 12 | 2.95 |
| Live births | 1 to 12 | 2.59 |
| Spontaneous abortions | 1 to 6 | 1.42 |
| Partners of mothers | Number | Percent |
| One partner | 211 | 77.9 |
| Two partners | 48 | 17.7 |
| Three partners | 9 | 3.3 |
| Four partners | 3 | 1.1 |
| Offspring by partner of mother | Number | Percent |
| 271 natural fathers of proband | 697 | 87.2 |
| 60 fathers of proband's half-siblings | 102 | 12.8 |
| Proband gender | Number | Percent |
| Female | 153 | 56.5 |
| Male | 118 | 43.5 |
| Proband lesion level | Number | Percent |
| Thoracic | 110 | 40.6 |
| Lumbar | 135 | 49.8 |
| Sacral | 21 | 7.7 |
| Missing | 5 | 1.8 |
Note: (1) One mother had a history of spontaneous abortion and also had a stillborn child.