Table 1.

Descriptive characteristics of sample at 17 weeks’ gestation (N = 15,963)

Characteristic	Mean ± SD or n (%)
Maternal age	30.48 ± 4.37
Parity
0	8,080 (50.62)
1+  Missing	7,753 (48.57) 130 (0.81)
Marital status
Married	7,722 (48.37)
Cohabiting	7,820 (48.99)
Single	354 (2.22)
Missing	67 (0.42)
Maternal education
> High school	11,960 (74.92)
High school and below	3,306 (20.71)
Missing	697 (4.37)
Paternal education
> High school	9,076 (56.86)
High school and below	5,668 (35.51)
Missing	1,219 (7.64)
Smoking
None	15,025 (94.12)
Sometimes	250 (1.57)
Daily	312 (1.95)
Missing	376 (2.36)
Alcohol use
None	12,836 (80.41)
1–3 drinks per month	1,257 (7.87)
1+ drinks per week	50 (0.31)
Missing	1,820 (11.40)

Note. SD = standard deviation