What is single embryo transfer?
Single embryo transfer is a procedure in which one best embryo, is placed in the uterus. The embryo selected for transfer might be a cryopreserved embryos (frozen)) or from the current fresh IVF cycle. The remaining embryos may be set aside for future use or cryopreservation.
Why Frozen embryo transfer is preferred in OHSS?
Controlled ovarian stimulation (COS) is an important part of IVF. It can induce the development of multiple follicles. Thus, COS produces higher levels of steroid hormones with the use of exogenous gonadotropin. Excessive stimulation of the ovaries can lead to life-threatening disease called ovarian hyperstimulation syndrome (OHSS).
This condition doesn’t develop overnight. Your doctor does serial ultrasound to predict such a situation. Your hormone levels will also tell whether you are going towards COS.
In this scenario, your embryo transfer is cancelled and embryos have to be cryopreserved. To avoid severe OHSS you must take enough vitamins and high protein diet during IVF treatment. This is an emergency condition and may need intensive care if severe.
Endometrial levels of natural killer cells and vascularization index in oocyte donors with stimulated cycles is more compared to natural cycles. Endometrial receptivity is altered under COS compared with natural cycle from the same patients. Hence it is preferable to go for frozen embryo transfer.