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Table 2 Odds ratios (ORs) of gastroschisis based on the pre-pregnancy body mass index (BMI)

From: Does overweight before pregnancy reduce the occurrence of gastroschisis?: the Japan Environment and Children’s Study

Pre-pregnancy BMINo. of womenNo. of gastroschisis
cases
Frequency of gastroschisisMaternal age at delivery adjusted OR95% confidence interval
Complete case analysis 
 < 18.5 kg/m2 (underweight)15,03420.012.2(0.4–11.0)
 18.5–24.9 kg/m2 (reference)67,77440.01Reference 
 ≥ 25.0 kg/m2 (overweight)986420.023.4(0.6–17.8)
(Situation 1) we categorised one mothera, who delivered an infant with gastroschisis and had no information on height and weight before pregnancy, as in the reference group 
 < 18.5 kg/m2 (underweight)15,03420.011.7(0.4–8.3)
 18.5–24.9 kg/m2 (reference)67,77550.01Reference 
 ≥ 25.0 kg/m2 (overweight)986420.022.7(0.5–13.5)
(Situation 2) we categorised one mothera, who delivered an infant with gastroschisis and had no information on height and weight before pregnancy, as in the underweight group. 
 < 18.5 kg/m2 (underweight)15,03530.013.1(0.7–13.6)
 18.5–24.9 kg/m2 (reference)67,77440.01Reference 
 ≥ 25.0 kg/m2 (overweight)986420.023.5(0.7–18.2)
(Situation 3) given situation 1, we re-categorised two cases of women with BMI < 18.5 kg/m2 as women of the reference group, because their BMI values were near 18.5 kg/m2 
 < 18.5 kg/m2 (underweight)15,03200  
 18.5–24.9 kg/m2 (reference)67,77770.01Reference 
 ≥ 25.0 kg/m2 (overweight)986420.022.0(0.4–9.8)
  1. a We had information on her weight just before delivery (57.5 kg), and using the average weight gain during pregnancy in this population (10.3 kg), we estimated her pre-pregnancy weigh to be 47.2 kg. Further, according to the 2014 Japanese National Health and Nutritional Survey, the mean height in women aged 30–39 years old was 158 cm; therefore, we estimated her pre-pregnancy BMI to be 18.9 kg/m2