Study procedures:
Recruitment:
Potentially eligible patients will be given information about the study and a copy of the informed consent documents on day 2 - 3 of their menstrual cycle, when the ovarian stimulation starts. On the day of freeze-all (3 days or 5 days after oocyte retrieval), screening for eligibility will be performed by treating physicians. Eligible couples will have about an hour to decide if they will participate in the study or not. If they choose to participate in the study, investigators will ask them to sign the consent form.
Once a participant signs an informed consent she is enrolled in the study. An individual record of all non-recruited patients and reasons for exclusion (at any stage) will be obtained and stored
Randomization:
Assignment to treatment allocation will be done via a web portal hosted by Hope Research Center, Viet Nam. The randomisation schedule will be computer-generated at Hope Research Center by using HRC (Hope Research Center) Epi software, in a 1:1 ratio, with a permuted random block size of 4 or 6.
Other standard assisted reproductive treatments are similar and parallel between the two groups, except for the use of Lipiodol® flushing in the intervention group. Due to the type of interventions, this study will only be blinded to clinicians who performed the embryo transfer and embryologists in the IVF clinics.
In the subsequent cycle, all patients in both groups will undergo frozen embryo transfer by using exogenous steroids regimen, starting from day 2 to day 4 of the menstrual cycle. Oral estradiol valerate (Progynova, Bayer Schering Pharma, Germany) 8 mg/day is given for 10-12 days. Ultrasound monitoring will be performed from day tenth onward. When endometrial thickness reaches greater than or equal to 8 mm, along with a triple-line pattern, micronized progesterone 800 mg will be administrated. Frozen embryo transfer (FET) will be performed 3-5 days after progesterone administration, depending on embryo staging. After FET, estradiol and progesterone supplementation are continued for all patients until the day of the pregnancy test. Patients with a positive pregnancy test will continue to receive luteal phase support regimen until 7 weeks of gestation.
All participants will be followed up per local protocol until outcomes are achieved