The researchers aim to determine how baseline (preconceptional) and first-trimester uterine artery Doppler measurements affect obstetric complications in women undergoing high-quality blastocyst transfer and to determine the correlation between the two Doppler measurements.

Only patients with high-quality blastocyst-stage embryos will be included in the study. In frozen embryo transfer cycles prepared hormonally, basal bilateral uterine artery Doppler velocimetry will be performed before treatment (preconception) in each patient.

Bilateral uterine artery Doppler velocimetry will be performed during the basal ultrasonography (2-5 days of menstruation). The absence of any uterine artery notches, diastolic or reverse flow will also be noted. In addition, sub-endometrial (arcuate artery) blood flows will be evaluated by Doppler ultrasonography.

For endometrial preparation, estrogen replacement will be given for approximately 12-14 days as a routine In cases with endometrial thickness ≥7mm, progesterone treatment will be started and embryo transfer will be planned on the 6th day of the treatment.

In the pregnant group, measurements will be repeated at the end of the first trimester (11-14 weeks) and uterine artery Doppler velocimetry will be reevaluated. In addition, patients will be followed up until delivery and possible obstetric complications will be recorded.

Baseline and first-trimester uterine artery Doppler ultrasonography findings will be compared with obstetric results. Obstetric outcomes such as birth weight at the end of pregnancy, small-large for gestational age, presence of hypertension, and preterm delivery will be correlated with preconceptional and first-trimester uterine artery Doppler parameters.

Inclusion Criteria:

• Exogenous hormone preparation of the endometrial lining
• High embryo quality ((≥2BB) according to Alpha criteria
• Embryo transfer at the blastocyst stage

Exclusion Criteria:

• Patients whose treatments were canceled for any reason before the embryo transfer procedure
• Patients who underwent embryo transfer in the cleavage stage
• Presence of low-quality (<2BB) blastocysts
• >15% loss of viability of the embryo during embryo thawing,
• Patients with congenital uterine malformations,
• Patients in whom Doppler velocimetry cannot be performed optimally

All patients who have artificial endometrial preparation with high-quality blastocysts between May 2022 and December 2022 will be included.