Table 3 Study characteristics

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