Number of birth defects

Singletons (N=1,246)

Multiples (N=256)

P

Total

Number of diseases in the same category

N

%

N

%

1

1,070

85.9

215

84.0

<0.05

2

135

10.8

23

9.0

1

61

12

2

74

11

3-

41

3.3

18

7.0

1

8

7

2

18

4

3-

15

7

χ2 test was performed for the 3x2 contingency table.