Natural Cycles With Spontaneous Versus Induced Ovulation in FET
Condition: Embryo Transfer
Study type: Observational

Summary: 
      In recent years, frozen-thawed embryo transfer procedure (FET) has been widely used to
      increase the cumulative pregnancy rate per IVF-cycle: which is the best preparation protocol
      remains a matter of debate.

      A retrospective analysis was conducted between 2012-2017. The aim was comparing clinical
      pregnancy rate (CPR) of pure natural cycle frozen-thawed embryo transfer (NC-FET) versus
      natural cycle frozen-thawed embryo transfer with hCG-triggered ovulation (mNC-FET).
    

Detailed description: 
      Compared to repeated oocyte retrieval procedure, frozen-thawed embryo transfer (FET) has been
      widely used to increase the cumulative pregnancy rate per IVF-cycle, with demonstrated
      superiority in preventing ovarian hyperstimulation syndrome and improving cost-efficiency and
      time to pregnancy.

      It is controversial whether triggering ovulation of the dominant follicle using human
      chorionic gonadotrophin (hCG) may benefit or reduce embryo implantation, when compared with a
      natural cycle environment. Unfavourable clinical outcomes of controlled ovarian stimulation
      have been reported by recently published studies, compared to the spontaneous LH surge.

      This study aimed to compare the effectiveness in terms of better clinical pregnancy rates
      (CPR) of pure natural cycle frozen-thawed embryo transfer (NC-FET) versus natural cycle
      frozen-thawed embryo transfer modified by HCG administration\with hCG-triggered ovulation
      (mNC-FET).

      A retrospective analysis was conducted between 2012-2017. In patients with regular ovulatory
      cycles, the timing of embryo thawing and transferring was based on spontaneous LH surge
      (NC-FET). Patients attended for ultrasound evaluation of the dominant follicle from Day 8 to
      10 of their menstrual cycle (depending on cycle length), detecting luteinizing hormone (LH)
      surge in urine/ taking an ovulation test for urinary LH measurement. In selected cases, a
      serum assays of LH, progesterone and estradioI has been further obtained. When the
      endometrial thickness reached 8 mm and dominant follicle 16-20 mm in diameter, hCG was
      administered in absence of urinary LH surge. Embryo thawing and transfer was planned 7 days
      after LH surge or HCG administration, whether G5 or G6 blastocyst. Exogenous progesterone
      supplementation started 2 days after hCG administration versus the same day of embryo
      transfer procedure in NC- ET. To limit potential confounders, only single blastocyst transfer
      cycles were included, vitrified on Days 5 or 6, excluding PGT-a (Pre Gestational Test for
      aneuploydia) cycles and cleavage stage embryo transfers. A unilevel and multi level logistic
      regression analysis was conducted using Stata Software versione15.
    

Intervention name(s): hCG administration before embryo transfer
Intervention type(s): Drug
Intervention description(s): Thawed embryo transfer with ovulation triggered by hCG
Other intervention name(s): Gonasi HP 5000 UI or Ovitrelle 250mg
Intervention MeSH terms: Chorionic Gonadotropin
Observational model: Case-Control
Time perspective: Retrospective
Sampling method: Non-Probability Sample
Study population: 
        2866 cycles were included in the analysis. To limit potential confounders, only single
        blastocyst transfer cycles were included, vitrified on Days 5 or 6, excluding PGT-a cycles
        and cleavage stage embryo transfers.