Table 2 Characteristics of participants included and excluded from analysis (data as mean ± SD or N (%))

Maternal age (years)

29.2 ± 5.2

30.1 ± 5.2

0.002

 White

150 (19.8%)

140 (28.1%)

0.001

 Black

497 (65.5%)

281 (56.3%)

 Other

112 (14.8%)

78 (15.6%)

 No

318 (41.9%)

167 (33.5%)

0.003

 Yes

441 (58.1%)

332 (66.5%)

 No

299 (39.4%)

256 (51.3%)

<.001

 Yes

460 (60.6%)

243 (48.7%)

 < $40,000

328 (43.2%)

149 (29.9%)

<.001

 $40,000–$80,000

210 (27.7%)

137 (27.5%)

 $80,000+

139 (18.3%)

144 (28.9%)

 Refused/did not answer

82 (10.8%)

69 (13.8%)

Gestational age^a

38.7 ± 1.8

38.8 ± 1.6

0.27

Birthweight z-score^b

−0.196 ± 0.972

− 0.005 ± 1.004

0.001

 No

492 (64.8%)

306 (61.3%)

0.21

 Yes

267 (35.2%)

193 (38.7%)

 Vaginal

456 (60.6%)

328 (65.9%)

0.061

 C-Section

296 (39.4%)

170 (34.1%)

 Winter

156 (20.6%)

101 (20.2%)

0.53

 Spring

182 (23.9%)

103 (20.6%)

 Summer

202 (26.6%)

143 (28.7%)

 Fall

219 (28.9%)

152 (30.5%)

 No

517 (68.1%)

394 (79%)

<.001

 Yes

242 (31.9%)

105 (21%)