The aim of our study was to investigate the correlation between the umbilical resistance index and weight gain during the third trimester of low-risk pregnancies.

Inclusion Criteria:

• Any pregnant patient with a normally progressing pregnancy and reporting for a prenatal screening ultrasound between 31 and 34 weeks amenorrhea.

Exclusion Criteria:

• -The lack of an ultrasound carried out during the first trimester to confirm the term of the pregnancy.
• A medical condition in the mother: diabetes, high blood pressure or a known chronic illness.
• A medical condition in the fetus: suspicion of fetal hypotrophy (fetal biometrics lower than the 10th percentile), a birth defect (a chromosomal abnormality) during the pregnancy.
• Patients with tobacco addiction.
• A body mass index (BMI) ≥ 30 before the pregnancy.
• Multiple pregnancies
• A gap of less than 4 weeks between the date of the ultrasound and the date of delivery.

Any pregnant patient with a normally progressing pregnancy and reporting for a prenatal screening ultrasound between 31 and 34 weeks amenorrhea.