Table 2 Hierarchical regression analysis of predictors of children’s IQ at 4 and 8 years old

Maternal age

.18

.11

n.s.

.20

.05

**

Primipara

.56

1.04

n.s.

1.14

.43

*

Gestational age

−.47

.31

n.s.

−.20

.12

n.s.

Self-reported smoking in pregnancy

−.81

1.26

n.s.

.64

.60

n.s.

Self-reported partner’s daily cigarette consumption

−.11

.06

n.s.

.02

.02

n.s.

Self-reported maternal smoking since birth

−2.22

1.64

n.s.

.68

.64

n.s.

Crowding

−1.53

.56

**

−1.36

.29

**

HOME score

1.43

.28

**

.56

.13

**

Maternal education

2.51

.45

**

2.85

.29

**

Paternal education

1.96

.40

**

2.40

.18

**

Maternal return to work

.57

.91

n.s.

−.41

.34

n.s.

Baby’s sex

2.91

.84

**

−.04

.39

.n.s.

Baby’s birthweight

.00

.00

**

.00

.00

**

Maternal depressive symptoms (32 weeks gestation)

−.14

.11

n.s.

−.14

.04

**

Mixed feeding at 1 month

1.82

1.30

n.s.

1.60

.53

**

Exclusive breastfeeding at 1 month

2.17

1.17

n.s.

2.2

.36

**

.02

.11

n.s.

.02

.05

n.s.