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Table 1 Demographic and reproductive characteristics, n = 2849

From: Perfluoroalkyl substances exposure in early pregnancy and preterm birth in singleton pregnancies: a prospective cohort study

Characteristicsn (%)
Maternal age (years)
  < 301811 (63.6)
 30–34845 (29.7)
  ≥ 35193 (6.8)
Pre-pregnancy BMIa(kg/m2)
  < 18.5435 (15.3)
 18.5–24.92119 (74.4)
  ≥ 25295 (10.4)
Parental educational level (years)
  ≤ 12142 (5.0)
  > 122707 (95.0)
Smoking status in early pregnancy
 No2831 (99.4)
 Yes9 (0.3)
 Unknown9 (0.3)
Parity
 02435 (85.5)
  ≥ 1414 (14.5)
Pregnancy complicated by chronic diseasesa
 No2653 (93.1)
 Yes196 (6.9)
Infant sex
 Male1456 (51.1)
 Female1393 (48.9)
Gestational age at blood drawn (weeks)
 Median (IQR)15 (13–16)
  1. aBMI body mass index; Chronic diseases including heart disease, kidney or liver disease, diabetes mellitus, chronic hypertension disorders, epilepsy, malnutrition and anemia; IQR interquartile range