Trans vaginal ultrasound with a partially full bladder will be done at gestational age earlier than 10 weeks to assess the site of intrauterine gestational sac to the endometrial cavity and the distance between the implantation site and the internal cervical os . Doppler assessment of the retrochorionic blood flow at the area behind the maximum chorionic tissue to detect resistance index.

Inclusion Criteria:

• Single intrauterine pregnancy
• Gestational age less than 10 weeks

Exclusion Criteria:

• Any condition distorting uterine cavity as myoma, uterine anomalies.
• Absent fetal pulsations
• Any condition needing termination of early pregnancy as molar pregnancy or severe deteriorating maternal disease

pregnant women at their early trimester with or without cesarean section scar