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386: Association between pregnancy complications and small for gestational age (SGA) birthweight defined by customized versus population-based standards

      Objective

      To estimate the association between pregnancy complications and SGA defined by customized fetal growth potential (custSGA) developed for our population compared with the population-based Alexander growth chart for the US (popSGA).

      Study Design

      A retrospective cohort study using our ultrasound database, with 54, 287 cases with complete data on pregnancy characteristics and outcome. SGA was defined as <10th percentile for gestational age by each growth standard. Outcome variables included: threatened preterm labor (PTL), preterm premature rupture of membranes (<37 weeks, PPROM), placental abruption (ABRPT), hypertensive disorders (HTNDZ= gestational hypertension and preeclampsia), neonatal care stay >7 days (NICU7) and stillbirth (SB).

      Results

      7551 (13.9%) of cases were cust SGA, of which 4063 (53.8%) were not identified as SGA by the population method. 3695 (6.8%) were popSGA, of which 207 cases (5.6%) were not SGA by the customised method. For each complication tested (Table), the cust SGA only category identified additional cases which were significantly associated with adverse outcome. In contrast, cases which were popSGA only were not associated with adverse outcome, with the exception of HTNDZ.
      Tabled 1
      custSGA & popSGA (OR, 95% CI)custSGA only (OR, 95% CIpopSGA only (OR, 95% CI)
      PTL1.1 (1.0-1.3)1.3 (1.2-1.4)0.9 (0.6-1.6)
      PPROM1.4 (1.1-1.7)2.3 (1.9-2.7)0.2 (0.03-1.7)
      ABRPT2.3 (1.7-3.1)2.4 (1.8-3.3)0.8 (0.1-6.0)
      HTNDZ2.7 (2.4-2.9)1.7 (1.6-1.9)1.6 (1.0-2.6)
      NICU73.5 (3.1-4.0)3.1 (2.7-3.6)0.8 (0.3 -2.1)
      SB9.3 (7.1-12.2)9.6 (7.4-12.3)1.7(0.2-11.9)

      Conclusion

      SGA defined by customized growth potential identifies pregnancies at the highest risk for complication by differentiating between physiologically and pathologically small fetuses.