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Table 1 Characteristics of participants (n = 186 mothers, n = 201 children) included in the present study

From: Prenatal exposure to phthalates and autism spectrum disorder in the MARBLES study

Characteristics Row total TD ASD Non-TD TD ASD Non-TD ASD versus TD a Non-TD versus TD a
n n %
Child’s sex         0.04 0.25
 Girl 79 46 13 20 46 28 36   
 Boy 122 54 33 35 54 72 64   
Birth year         0.04 0.21
 2007 11 7 1 3 7 2 5   
 2008 35 26 3 8 26 7 15   
 2009 46 23 11 13 23 24 24   
 2010 31 15 8 8 15 17 15   
 2011 19 9 6 4 9 13 7   
 2012 17 7 8 2 7 17 4   
 2013 34 10 9 15 10 20 27   
 2014 5 3 0 2 3 0 4   
Child’s race/ethnicity         0.19 0.07
 White (non-Hispanic) 195 95 45 55 53 37 35   
 Hispanic 6 5 1 0 26 37 31   
 Other b 195 95 45 55 21 26 35   
Birth Status         0.42 0.09
 Singleton 195 95 45 55 95 98 100   
 Has a twin 6 5 1 0 5 2 0   
Gestational age at delivery         0.10 0.14
  ≤ 37 weeks 18 13 2 3 13 4 6   
  > 37 weeks 180 85 44 51 87 96 94   
Maternal pre-pregnancy BMI         0.21 0.41
 Normal/ underweight 103 57 20 26 58 43 48   
 Overweight 48 22 13 13 22 28 24   
 Obese 46 19 12 15 19 26 28   
 Missing 1 0 1 0 0 2 0   
Maximum parental education         0.56 0.43
 Less than college degree 62 29 15 18 28 36 38   
 Bachelor’s degree 87 49 20 18 48 48 38   
 Graduate or professional degree 43 24 7 12 24 17 25   
Mother’s age at delivery         0.13 0.68
  < 35 years 105 56 20 29 57 43 54   
  ≥ 35 years 93 42 26 25 43 57 46   
Father’s age at delivery         0.18 0.51
  < 35 years 75 38 12 21 39 27 40   
  ≥ 35 years 118 58 31 30 60 69 57   
 Missing 5 1 2 2 1 4 4   
Prenatal vitamin use in the first month of pregnancy         0.00 0.37
 Yes 105 61 15 29 62 33 54   
 No 85 36 26 23 37 57 43   
 Missing 8 1 5 2 1 11 4   
Homeowner         0.07 0.37
 Yes 117 64 23 30 65 50 56   
 No 75 33 20 22 34 43 41   
 Missing 6 1 3 2 1 7 4   
Parity         0.08 0.32
 0 c 2 2 0 0 2 0 0   
 1 80 44 14 22 45 30 41   
  > 1 110 51 29 30 52 63 56   
 Missing 6 1 3 2 1 7 4   
Mom ever smoked         0.13 0.46
 Yes 70 31 20 19 32 43 35   
 No 123 66 24 33 67 52 61   
 Missing 5 1 2 2 1 4 4   
Season of conception (months)         0.29 0.30
 Cold (November – April) 100 54 21 25 55 46 46   
 Warm (May – October) 98 44 25 29 45 54 54   
Number of urine samples collected         0.60 0.09
 1–2 35 17 9 8 17 20 15   
 3–4 54 23 16 16 23 35 30   
 5–6 37 24 8 7 24 17 13   
 7–8 57 30 11 15 31 24 28   
 9–12 15 4 2 8 4 4 15   
  1. aP-value from the Pearson’s chi-squared test
  2. bIncludes Black, Asian, and multiracial
  3. cOne of them has an identical twin sister with an autistic child, and the other mother has multiple siblings with autism. These two mothers were included in the current study because they have high-risk ASD genetic factors and exclusion of them did not change the results
  4. Note: Eleven mothers participated in the study for two different pregnancies and one mother participated for three different pregnancies over 4 years. Three pregnancies resulted in twins