Table 1.

Characteristics associated with missing body mass index (calculated using height and weight) in the National Birth Defects Prevention Study control mothers (1997–2009)

	Missing N (%)	Not missing N (%)	Crude odds ratio	95 % CI	Adjusted odds ratioa	95 % CI
Total	435 (4.6)	9640 (95.4 %)
Maternal age at EDD
<18	18 (5.1)	333 (94.9)	Reference		Reference
18–24	170 (5.8)	2821 (94.3)	1.1	0.7, 1.8	1.4	0.8, 2.7
25–29	125 (4.5)	2652 (95.5)	0.9	0.5, 1.4	1.4	0.7, 2.6
30–34	91 (3.6)	2468 (96.4)	0.7	0.4, 1.1	1.4	0.7, 2.8
35+	31 (2.2)	1366 (97.8)	0.4	0.2, 0.8	0.8	0.4, 1.8
Race/ethnicity
Non-Hispanic white	32 (0.6)	5830 (99.4)	Reference		Reference
Non-Hispanic black	7 (0.6)	1102 (99.4)	1.2	0.5, 2.6	0.3	0.1, 0.9
Hispanic	370 (15.6)	2010 (84.5)	33.5	23.3, 48.3	2.0	1.2, 3.4
Other	26 (3.6)	689 (96.4)	6.9	4.1, 11.6	1.1	0.6, 2.2
Maternal education
<12 years	284 (17.0)	1384 (83.0)	5.7	4.4, 7.4	2.3	1.7, 3.1
12 years	82 (3.5)	2293 (96.5)	Reference		Reference
Some college	24 (0.9)	2640 (99.1)	0.2	0.2, 0.4	0.5	0.3, 0.8
College graduate	15 (0.5)	3142 (99.5)	0.1	0.1, 0.2	0.4	0.2, 0.7
Language of interview
English	152 (1.7)	8987 (98.3)	Reference		Reference
Spanish	252 (29.2)	611 (70.8)	24.4	19.6, 30.3	2.4	1.8, 3.2
Country of birth
USA	40 (0.5)	7790 (99.5)	Reference		Reference
Other	365 (17.9)	1675 (82.1)	42.4	30.5, 59.1	8.6	5.5, 13.4
Parity
First birth	124 (3.1)	3879 (96.9)	Reference		Reference
≥Second birth	297 (4.9)	5758 (95.1)	1.6	1.3, 2.0	1.1	0.8, 1.5
Folic acid use (B1)
No	389 (5.7)	6465 (94.3)	Reference		Reference
Yes	32 (1.0)	3134 (99.0)	0.2	0.1, 0.2	0.5	0.3, 0.7
Smoking (B1)
No	392 (4.8)	7743 (95.2)	Reference		Reference
Yes	18 (1.0)	1746 (99.0)	0.2	0.1, 0.3	0.7	0.4, 1.3
Alcohol (B1)
No	372 (5.5)	6384 (94.5)	Reference		Reference
Yes	36 (1.2)	3069 (98.8)	0.2	0.1, 0.3	0.7	0.4, 1.0

EDD estimated due date, B1 1 month before conception

^aEstimates are adjusted for all other variables presented in the table