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. Author manuscript; available in PMC: 2016 Feb 4.
Published in final edited form as: Paediatr Perinat Epidemiol. 2013 Oct 10;28(1):3–10. doi: 10.1111/ppe.12083

Table 4.

Maternal demographic and pregnancy characteristics associated with incongruenta obstetric estimate of gestational age compared with ultrasound-based estimates: California Statewide Expanded Alpha Fetoprotein Prenatal Screening Program, April–December 2007

% Underb % Overc OR [95% CI] Adjusted OR [95% CI]d
Race/ethnicity
  White, non-Hispanic 1.2 0.9 1.0 [Reference] 1.0 [Reference]
  Black, non-Hispanic 2.1 1.6 1.7 [1.5, 1.9] 1.4 [1.3, 1.6]
  Hispanic 2.1 2.0 2.0 [1.8, 2.1] 1.4 [1.3, 1.5]
  Asian 1.5 1.1 1.2 [1.1, 1.4] 1.3 [1.2, 1.4]
  Other 1.6 1.2 1.3 [0.8, 2.1] 1.1 [0.6, 1.7]
Maternal age (years)
  <20 2.7 1.7 1.5 [1.3, 1.6] 1.1 [1.0, 1.2]
  20–24 2.0 1.9 1.3 [1.2, 1.4] 1.1 [1.0, 1.1]
  25–34 1.7 1.4 1.0 [Reference] 1.0 [Reference]
  ≥35 years 1.8 1.6 1.1 [1.0, 1.2] 1.1 [1.0, 1.2]
Maternal education (years)
  <12 2.5 2.2 2.4 [2.2, 2.7] 1.7 [1.5, 1.9]
  12 2.0 1.8 2.0 [1.8, 2.1] 1.5 [1.4, 1.7]
  13–15 1.5 1.3 1.4 [1.3, 1.6] 1.2 [1.1, 1.4]
  ≥16 1.2 0.8 1.0 [Reference] 1.0 [Reference]
Delivery insurance
  Public 2.3 2.1 1.7 [1.6, 1.8] 1.2 [1.1, 1.3]
  Private 1.5 1.1 1.0 [Reference] 1.0 [Reference]
  None/other 1.6 1.4 1.2 [1.0, 1.4] 1.1 [0.9, 1.3]
Prepregnancy BMI
  Underweight (<18.5 kg/m2) 1.9 1.1 1.0 [0.9, 1.2] 1.1 [0.9, 1.2]
  Normal (18.5–24.9 kg/m2) 1.8 1.2 1.0 [Reference] 1.0 [Reference]
  Overweight (25.0–29.9 kg/m2) 1.8 1.6 1.1 [1.0, 1.2] 1.0 [0.9, 1.1]
  Obese (≥30.0 kg/m2) 1.7 2.0 1.3 [1.2, 1.4] 1.1 [1.0, 1.2]
  Missing 2.4 2.4 1.6 [1.5, 1.8] 1.4 [1.3, 1.5]
Parity
  0 1.9 1.3 1.0 [Reference] 1.0 [Reference]
  1 1.6 1.6 1.0 [1.0, 1.1] 1.0 [0.9, 1.1]
  ≥2 2.0 2.0 1.3 [1.2, 1.4] 1.1 [1.0, 1.2]
Smoking during pregnancy
  None 1.8 1.6 1.0 [Reference] 1.0 [Reference]
  Any 2.0 1.2 0.9 [0.8, 1.1] 1.0 [0.8, 1.2]
a

>14 days absolute difference between obstetric-based and ultrasound-based estimates of gestational age.

b

Percent of population for which obstetric estimate was earlier than ultrasound-based estimate of gestational age.

c

Percent of population for which obstetric estimate was later than ultrasound-based estimate of gestational age.

d

Adjusted for all variables simultaneously.