This study aims to evaluate the patterns of aortic isthmus Doppler in fetuses diagnosed with early fetal growth restriction (FGR) and to correlate these findings with the severity of FGR and other Doppler parameters.

A cross-sectional comparative observational study will be conducted on singleton pregnant women attending the fetal medicine unit at Assiut University Hospital. Participants will be divided into two groups: fetuses with FGR and normal controls.

Doppler measurements including aortic isthmus indices, uterine artery, umbilical artery, middle cerebral artery, cerebroplacental ratio, and ductus venosus will be assessed at a single time point. The study will help to clarify the clinical value of aortic isthmus Doppler in early detection and assessment of fetal compromise in FGR cases.

Fetal growth restriction (FGR) is a major contributor to perinatal morbidity and mortality and is commonly associated with placental insufficiency. Early identification of fetal compromise remains a significant clinical challenge. Doppler assessment of fetal circulation has been widely used to monitor affected fetuses, including evaluation of the umbilical artery, middle cerebral artery, and ductus venosus.

The aortic isthmus represents a critical vascular junction reflecting the balance between cerebral and placental circulation. Changes in aortic isthmus Doppler patterns may provide early insights into fetal hemodynamic adaptation and deterioration in cases of FGR.

This cross-sectional comparative observational study will be conducted at the fetal medicine unit, Women's Health Hospital, Assiut University. The study population will include singleton pregnancies diagnosed with FGR (EFW <10th percentile) and a control group of normal fetuses.

Participants will undergo a single-time Doppler assessment including fetal biometry, uterine artery PI, umbilical artery PI, middle cerebral artery PI, cerebroplacental ratio, ductus venosus PI, and aortic isthmus Doppler indices. The aortic isthmus flow will be classified based on the isthmic flow index (IFI) into five categories, reflecting progressive hemodynamic changes.

The primary objective is to determine the correlation between aortic isthmus Doppler changes and the severity of FGR based on estimated fetal weight percentiles. Secondary objectives include correlation of aortic isthmus findings with cerebroplacental ratio and ductus venosus parameters.

This study is designed as a pilot exploratory study due to limited previous data. Results are expected to enhance understanding of fetal hemodynamics and potentially improve monitoring strategies in pregnancies complicated by FGR.

Inclusion Criteria:

• Singleton pregnancy
• Diagnosis of fetal growth restriction (estimated fetal weight <10th percentile for gestational age)
• Written informed consent obtained from the patient

Exclusion Criteria:

• Major fetal structural anomalies, especially cardiovascular anomalies
• Multiple pregnancy (e.g., twins)
• Suspected chromosomal abnormalities or genetic syndromes
• Severe maternal comorbidities affecting Doppler results (e.g., uncontrolled diabetes, lupus)
• Uncertain gestational age
• Fetal demise before Doppler assessment

Singleton pregnant women attending the fetal medicine unit at Women's Health Hospital, Assiut University, including both fetal growth restriction cases and normal controls.