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Table 1 Descriptive statistics for birth weight, small for gestational age and preterm births by socio-demographics and mother characteristics among all singleton births born in Eastern Massachusetts between 1996 and 2002

From: The effects of socioeconomic status and indices of physical environment on reduced birth weight and preterm births in Eastern Massachusetts

Categorical variables All births (% of total) Mean birth weight (in grams) (SD) Small for gestational age N (%) Preterm birth N (%) Comparison group (≥ 37 weeks; ≥ 2500 grams) N (%)
Mother race          
   White 75.3 3463 (545) 32103 76.2 22160 66.8 266329 76.0
   African-American 7.4 3236 (638) 2938 7.0 3994 12.0 24530 7.0
   Asian 6.0 3241 (510) 2471 5.9 2194 6.6 20900 6.0
   Hispanic 11.0 3306 (565) 4531 10.8 4730 14.3 37691 10.8
   Native American 0.2 3371 (581) 66 0.2 68 0.2 537 0.2
   Missing 0.1 3426 (622) 0 0 38 0.1 417 0.1
Mother education          
   Primary and secondary (≤ 8 years) 2.6 3296 (561) 1307 3.1 1126 3.4 8073 2.3
   High school (>8 – 12 years) 29.0 3338 (576) 15190 36.1 11453 34.5 96981 27.7
   Some college (13 – 15 years) 39.9 3481 (533) 13354 31.7 11012 33.2 145698 41.6
   College or postgraduate 22.6 3433 (562) 9118 21.7 7269 21.9 79975 22.8
   (≥ 16 years)          
   Missing 5.9 3333 (573) 3140 7.5 2324 7.0 19677 5.6
APNCU          
   None 0.6 3267 (714) 251 0.6 337 1.0 1825 0.5
   Inadequate 7.8 3308 (571) 4511 10.7 3147 9.5 25652 7.3
   Intermediate 8.0 3487 (509) 3842 9.1 1036 3.1 28985 8.3
   Appropriate 48.1 3507 (487) 20185 47.9 3263 9.8 181619 51.8
   Appropriate plus 35.5 3301 (627) 13320 31.6 25401 76.5 112323 32.1
Mother age at birth          
   <20 8.9 3246 (565) 5616 13.3 4020 12.1 28308 8.1
   20 – 29 36.6 3389 (550) 16783 39.9 12007 36.2 127149 36.3
   30 – 34 33.7 3465 (546) 12143 28.8 10017 30.2 121240 34.6
   35 – 39 17.4 3462 (574) 6196 14.7 5762 17.4 61997 17.7
   >39 3.4 3422 (600) 1371 3.3 1378 4.2 11710 3.3
Number of cigarettes smoked during pregnancy (per day)          
   None 90.0 3438 (555) 33410 79.3 29001 87.4 320511 91.5
   Any amount 9.8 3208 (558) 8655 20.6 4115 12.4 29301 8.4
   Missing 0.2 3369 (648) 44 0.1 68 0.2 592 0.2
Number of cigarettes smoked before pregnancy (per day)          
   None 83.0 3437 (556) 30580 72.6 26896 81.1 295766 84.4
   Any amount 16.6 3309 (566) 11398 27.1 6120 18.4 53238 15.2
   Missing 0.4 3384 (620) 131 0.3 168 0.5 1400 0.4
Previous infant ≥ 4000 grams          
   None 98.6 3411 (556) 41851 99.4 32730 98.6 344956 98.4
   Yes 0.9 3938 (546) 63 0.1 175 0.5 3626 1.0
   Missing 0.5 3355 (712) 195 0.5 279 0.8 1822 0.5
Previous preterm birth          
   None 98.6 3419 (556) 41256 98.0 31946 96.3 346553 98.9
   Yes 0.9 3011 (678) 658 1.6 959 2.9 2029 0.6
   Missing 0.5 3355 (712) 195 0.5 279 0.8 1822 0.5
Gender of infant          
   Male 51.2 3473 (572) 21631 51.4 18172 54.8 178071 50.8
   Female 48.8 3355 (540) 20478 48.6 15012 45.2 172333 49.2
  1. APNCU – adequacy of prenatal care utilization; N – number; SD – standard deviation