Table IV.

Associations between smoking (continuous and categorical variable) and fetal growth parameters: second trimester head circumference, abdominal circumference femur length and birth weight.

	Model 1a	P	Model 2b	P
	Effect estimate (β), 95% CI		Effect estimate (β), 95% CI
Head circumference
Cigarettes/day	0.010 (−0.051; 0.071)	0.743	−0.003 (−0.064; 0.058)	0.924
Smoking None	0 (Reference)		0 (Reference)
1–9 cigarettes/day	0.283 (0.056; 0.510)	0.015*	0.290 (0.065; 0.514)	0.012*
≥10 cigarettes/day	−0.069 (−0.353; 0.214)	0.631	−0.134 (−0.413; 0.144)	0.345
Abdominal circumference
Cigarettes/day	−0.043 (−0.110; 0.031)	0.279	−0.053 (−0.121; 0.015)	0.129
Smoking None	0 (Reference)		0 (Reference)
1–9 cigarettes/day	0.000 (−0.250; 0.249)	0.997	0.023 (−0.231; 0.277)	0.861
≥10 cigarettes/day	−0.199 (−0.511; 0.113)	0.211	−0.261 (−0.576; 0.054)	0.104
Femur length
Cigarettes/day	−0.077 (−0.144; −0.011)	0.022*	−0.077 (−0.147; −0.008)	0.029*
Smoking None	0 (Reference)		0 (Reference)
1–9 cigarettes/day	−0.111 (−0.360; 0.137)	0.380	−0.095 (−0.353; 0.163)	0.471
≥10 cigarettes/day	−0.323 (−0.633; −0.012)	0.042*	−0.321 (−0.641; −0.001)	0.049*
Birth weight
Cigarettes/day	−0.145 (−0.227; −0.063)	0.001*	−0.150 (−0.233; −0.068)	0.000*
None	0 (Reference)		0 (Reference)
1–9 cigarettes/day	−0.314 (−0.621; −0.008)	0.044*	−0.306 (−0.612; 0.001)	0.050
≥10 cigarettes/day	−0.519 (−0.904; −0.135)	0.008*	−0.560 (−0.941; −0.178)	0.004*

Growth parameters are expressed as Z-scores, which are corrected for gestational age. Birth weight is expressed as Z-score, which is corrected for gender and gestational age.

^* P < 0.05 (bold text).

^aCrude model.

^bFully adjusted model adjusted for alcohol use, educational level, folic acid supplement use, maternal age, mode of conception, ethnicity, fetal gender, maternal BMI, parity and vitamin use.