Table 3.
Study characteristics
| Characteristic | N | % |
|---|---|---|
| All births |
691 |
100 |
| All scans |
2,848 |
100 |
| Infant sex |
|
|
| Male |
354 |
51 |
| Female |
337 |
49 |
| Maternal age (years) |
|
|
| Less than 20 |
58 |
8 |
| 20–24 |
132 |
19 |
| 25–29 |
210 |
30 |
| 30–34 |
201 |
29 |
| 35 or over |
90 |
13 |
| Birth order |
|
|
| First birth |
308 |
45 |
| Second birth |
215 |
31 |
| Third birth |
108 |
16 |
| Fourth birth or more |
60 |
9 |
| Scans per gestation period |
|
|
| 14–17 weeks |
147 |
5 |
| 18–22 weeks |
578 |
20 |
| 23–27 weeks |
561 |
20 |
| 28–32 weeks |
550 |
19 |
| 33–39 weeks |
991 |
34 |
| 40–42 weeks |
21 |
1 |
| Scans per individual |
|
|
| 2–3 scans |
190 |
28 |
| 4–5 scans |
459 |
66 |
| 6–8 scans | 42 | 6 |