This study aims to characterize neonatal clinical risk profiles in relation to prenatal obstetric characteristics in infants with early fetal growth restriction (early-FGR) secondary to Doppler flowmetry alterations. The primary objective is to analyze the association between maternal and obstetric factors-such as preeclampsia, diabetes, and the timing and progression of Doppler changes-and neonatal clinical outcomes. The research evaluates how these relationships vary based on the prenatal flowmetric profile (umbilical artery [UA] with absent end-diastolic flow [UA bs-], UA with reversed end-diastolic flow [UA bs+], or UA alterations combined with ductus venosus [DV] changes) compared to preterm infants without FGR. Conducted as a spontaneous, multicenter, observational study with both retrospective and prospective components, the research involves mothers and their preterm neonates. The study population includes cases defined as neonates with a gestational age of 32 weeks or less and/or a birth weight under 1500 grams, with a prenatal history positive for FGR (fetal weight or abdominal circumference/fetal weight ratio below the 10th percentile) and documented fetal or utero-placental Doppler alterations. The control group consists of neonates within the same gestational age or weight criteria but without evidence of FGR or flowmetric alterations. Exclusion criteria apply to fetuses with known or suspected malformations or genetic anomalies, cases involving maternal substance abuse during pregnancy, and multiple pregnancies. With a total duration of 30 months, including 12 months for enrollment and 6 months for data analysis, the study targets a sample size of 850 subjects, comprising approximately 600 controls and 200 FGR cases. The statistical analysis will focus on pre-specified outcomes to assess the associations between maternal/obstetric factors and neonatal health, stratified by Doppler profile. Continuous variables will be summarized as mean and standard deviation or median and interquartile range, while categorical variables will be expressed as absolute frequencies and percentages. Group comparisons will utilize parametric or non-parametric tests based on data distribution. The main analysis will employ logistic regression models for binary outcomes and linear regression models for continuous outcomes, utilizing clustered standard errors by center to account for the multicenter design. Candidate covariates include gestational age, sex, and key maternal conditions such as preeclampsia, diabetes, pathological cardiotocography (CTG), and the timing of Doppler changes. To manage a high number of predictors relative to the sample size, penalization techniques such as lasso or elastic net will be applied for automatic covariate reduction and estimation stabilization. Subsequent analyses, including interaction models, will focus on the covariates selected through these procedures to provide a comprehensive understanding of how prenatal hemodynamic compromises influence the clinical trajectory of the preterm neonate.

This study, titled "Characterization of clinical neonatal risk profiles in relation to prenatal obstetric characteristics in infants with Early Fetal Growth Restriction (FGR) secondary to Doppler flowmetry alterations," is designed as a multicenter, spontaneous, observational investigation combining both retrospective and prospective data collection to analyze the complex interplay between maternal-fetal hemodynamics and neonatal outcomes. The primary objective is to evaluate the association between specific maternal and obstetric factors-including preeclampsia, gestational diabetes, the timing of onset, and the longitudinal progression of Doppler alterations-and the resulting clinical neonatal outcomes. A key focus of the research is to determine how these relationships fluctuate according to the specific prenatal flowmetric profile, categorized by umbilical artery (UA) end-diastolic flow status (UA bs-, UA bs+, or UA combined with ductus venosus [DV] alterations), in comparison to a control group of preterm infants who did not experience FGR. The study population consists of mothers and their preterm neonates, specifically targeting those with a gestational age of 32 weeks or less and/or a birth weight under 1500 grams. The case group includes neonates with a documented prenatal history of FGR, defined by a fetal weight or abdominal circumference-to-fetal weight ratio below the 10th percentile, accompanied by abnormal fetal or utero-placental Doppler flowmetry. Conversely, the control group comprises neonates of similar gestational age or weight who showed no prenatal evidence of growth restriction or Doppler abnormalities. To maintain the integrity of the data regarding vascular-driven growth restriction, the study excludes pregnancies involving fetal malformations, known or suspected genetic anomalies, maternal substance abuse, and multiple gestations. Conducted over a total duration of 30 months, the timeline allocates 12 months for patient enrollment and selection and 6 months for comprehensive data analysis. The targeted sample size is 850 subjects, consisting of 600 neonates without an FGR diagnosis and 200 with a confirmed FGR diagnosis. The statistical methodology is rigorous and tailored to the multicenter nature of the study, synthesizing continuous variables as mean with standard deviation or median with interquartile range, while categorical variables will be presented as absolute frequencies and percentages. Exploratory comparisons between groups will utilize parametric or non-parametric tests based on data distribution. The primary analysis will employ logistic regression models for binary outcomes and linear regression models for continuous outcomes, utilizing clustered standard errors by center to account for intra-center correlation. Candidate covariates for these models include gestational age, sex, and significant maternal or obstetric conditions such as preeclampsia, diabetes, pathological cardiotocography (CTG), and the specific timing and progression of Doppler changes. In instances where the number of predictors is high relative to the statistical units, penalization techniques such as lasso or elastic net will be applied for automatic covariate reduction and estimate stabilization, ensuring that subsequent analyses and interaction studies focus on the most statistically relevant predictors. Informed consent is a mandatory prerequisite for participation, ensuring ethical standards are maintained throughout the retrospective and prospective phases of the study.

Inclusion Criteria:

• Cases: neonates with a gestational age ≤32 weeks and/or birth weight < 1500 g, with a prenatal history positive for FGR (fetal weight < 10th percentile and/or abdominal circumference/fetal weight ratio < 10th percentile) and abnormal fetal and/or utero-placental Doppler findings
• Controls: neonates with a gestational age ≤32 weeks and/or birth weight < 1500 g, without prenatal evidence of FGR or Doppler flow abnormalities
• Obtaining informed consent.

Exclusion Criteria:

• Fetal malformations and/or suspected or known genetic anomalies
• Maternal substance abuse during pregnancy
• Twin pregnancies.

Mothers and their preterm neonates, including both subjects with FGR and Doppler alterations (UA bs-, UA bs+, UA+DV) and controls without evidence of FGR or flow velocity alterations.