Quantitative Discrimination of Small for Gestational Age (Sga) Singleton Newborns. Incidences, Risk Factors and Foetal Outcomes of the Three Major Subtypes of Sga: A 23-Year Cohort of 8,601 Singleton Sga (Out of 83,917 Births)

Objectives: Quantifying the different sorts of small for gestational age (SGA): constitutional SGA vs fetal growth restriction (FGR, i.e. Doppler anomalies), and verifying if the most frequent cause of FGR is associated with maternal preeclampsia. Design: University’s maternity, 23.5 year-observational population-based cohort study. All consecutive singleton pregnancies. Main outcome Measures: Comparing risk factors between the different types of SGA’s and controls (pregnancies without preeclampsia and SGA). Results: There were 8,601 SGA/ 83,617 malformations excluded births (10.2%). Those associated with maternal preeclampsia (PES, N= 536) represented 6.2% of all SGA, those without maternal preeclampsia but diagnosed with having Doppler anomalies « vascular SGA » (VascS, N= 1,389) represented 16.1%. The remaining N= 6,676, without Doppler anomalies “constitutional SGA” (constS) comprised ¾ (77.6%) of all SGA. Singleton pregnancies without any hypertensive disease and without SGA (N= 75,316) represented the control group. Preeclamptic mothers were on average older than controls 28.5 years vs 27.9, p=0.03. VascS and constS being younger 27.3, p<0.0001. Pre-pregnancy BMI was 25.9 kg/m² in PES vs 25.0 in controls (p< 0.0001), while it was significantly lower (24.0) in VascS and constS. In multiparas, the rate of primipaternity for the index pregnancy was much higher in PES and VascS (16.5%) compared with controls (4%) and ConstS (4.7%); OR 4.8, p< 0.0001. A history of prior preeclampsia had a similar effect in VascC and ConstS: adjOR ≈ 1.5, while a history of previous SGA had a major effect (OR 4.9). The date of delivery in the constitutional SGA group was the same than controls. Conclusions: First, 77%, of SGA (small for gestational age, 10% of all births) were constitutional with no special risk for the newborn. Severely ill SGA (FGR) represented only one quarter (23%) of all SGA. Second, but main findings: three quarters of these FGR belonged to pregnancies without any detectable maternal disease (preeclampsia). FGR associated with maternal preeclampsia comprized only one quarter of FGR.