Table I.

Baseline characteristics of participants.

Maternal characteristics	Smoking women				Non-smoking women		P
	N = 96				N = 593
	Smoking 1–9 cigarettes/day N = 60	Missing	Smoking ≥10 cigarettes/day N = 36	Missing	Missing
Age, years, mean (±SD)	31.1 (4.4)	0	30.7 (4.3)	0	32.6 (4.4)	0	0.002*
Nulliparous, total N (%)	37 (62)	0	21 (58)	0	321 (54)	0	0.493
BMI, kg/m2, median (IQR)	24.2 (21.8–27.6)	0	26.9 (23.3–30.0)	0	24.0 (21.8–27.6)	0	0.032*
Geographic origin		0		0		0	0.558
Western, N (%)	51 (85)		33 (92)		505 (85)
Non-western, N (%)	9 (15)		3 (8)		88 (15)
Educational level		2		0		9	<0.001*
Low, N (%)	3 (5)		6 (17)		42 (7)
Middle, N (%)	32 (55)		18 (50)		185 (32)
High, N (%)	23 (40)		12 (33)		357 (61)
Alcohol, total, N (%)	36 (60)	0	16 (44)	0	155 (26)	0	<0.001*
Periconceptional folic acid, total, N (%)	41 (68)	0	29 (81)	0	516 (87)	0	0.003*
Vitamin use, N (%)	38 (64)	1	22 (61)	0	397 (67)	0	0.705
Mode of conception		0		0		0	0.070
Naturally conceived, N (%)	39 (65)		18 (50)		293 (49)
IVF/ICSI conceived, N (%)	21 (35)		18 (50)		300 (51)
1st trimester ultrasound
Available measurements per participant, median (IQR)	2 (2–3)	0	2 (1–3)	0	2 (1–3)	0	0.204
2nd trimester ultrasound
Head circumference Z-score, mean (±SD)	0.48 (0.86)	3	0.11 (0.86)	2	0.17 (0.81)	49	0.026*
Abdominal circumference Z-score, mean (±SD)	0.82 (0.96)	3	0.60 (0.91)	2	0.80 (0.87)	50	0.425
Femur length Z-score, mean (±SD)	0.30 (0.91)	3	0.06 (1.02)	2	0.39 (0.88)	50	0.106
Birth outcomes
Birth weight, g, median (IQR)	3240 (2875–3485)	1	3330 (2685–3580)	1	3375 (3045–3706)	15	0.062
Birth weight, percentiles, median (IQR)	36.5 (14.3–63.5)	2	27 (5.5–59.5)	1	47 (24–75)	15	0.004*
Gestational age at birth, median (IQR)	271 (265–280)	2	274 (265–284)	1	274 (267–282)	15	0.834
Small for gestational age (<10th percentile), N (%)	11 (19)	2	12 (36)	1	65 (12)	45	<0.001*
Males, N (%)	29 (48)	0	24 (67)	0	283 (49)	9	0.104

^*Significance at P ≤ 0.05 assessed by ANOVA.

IQR, interquartile range.