Table III.

Stratified analysis for mode of conception: associations between maternal periconceptional smoking and Carnegie stages for IVF/ICSI conceived pregnancies.

		Model 1a	P	Model 2b	P
		Effect estimate (β), 95% CI		Effect estimate (β), 95% CI
Naturally conceived (N = 350)	Smoking
	No (N = 293)	0 (Reference)		0 (Reference)
	Yes (N = 53)	0.068 (−0.213; 0.349)	0.635	0.164 (−0.132; 0.459)	0.276
	Cigarettes/day	−0.020 (−0.118; 0.077)	0.683	0.009 (−0.093; 0.111)	0.867
	Smoking, categorical
	None (N = 293)	0 (Reference)		0 (Reference)
	1–9 cigarettes/day (N = 39)	0.232 (−0.096; 0.561)	0.166	0.313 (−0.030; 0.656)	0.073
	≥10 cigarettes/day (N = 18)	−0.298 (−0.773; 0.176)	0.217	−0.170 (−0.659; 0.320)	0.496
IVF/ICSI conceived (N = 339)	Smoking
	No (N = 300)	0 (Reference)		0 (Reference)
	Yes (N = 39)	−0.263 (−0.479; −0.047)	0.017*	−0.305 (−0.544; −0.067)	0.012*
	Cigarettes/day	−0.112 (−0.181; −0.043)	0.001*	−0.126 (−0.200; −0.051)	0.001*
	Smoking, categorical
	None (N = 300)	0 (Reference)		0 (Reference)
	1–9 cigarettes/day (N = 21)	−0.082 (−0.366; 0.203)	0.572	−0.131 (−0.443; 0.181)	0.409
	≥10 cigarettes/day (N = 18)	−0.479 (−0.787; −0.170)	0.002*	−0.510 (−0.834; −0.186)	0.002*

^* P < 0.05 (bold text).

^aModel with gestational age as time predictor.

^bFully adjusted model with gestational age as time predictor; adjusted for alcohol use, educational level, folic acid supplement use, maternal age, ethnicity, fetal sex, maternal BMI, parity and vitamin use.