A RCT Comparing Spontaneous Natural Cycles and Human Chorionic Gonadotrophin-induced Natural Cycles in FET
Condition: Subfertility; Pregnancy
MeSH terms: Infertility
Study type: Interventional

Summary: 
      This is a randomized controlled trial on the comparison of the ongoing pregnancy rate in
      frozen-thawed embryo transfer cycles with spontaneous ovulation and hCG-induced natural
      cycles.
    

Detailed description: 
      Embryo cryopreservation is essential nowadays. It allows the usage of surplus good quality
      embryos in frozen-thawed embryo transfer (FET) cycles which avoids embryo wastage and
      facilitates the adoption of transferring a small number of embryos in the fresh stimulation
      cycle so as to reduce the risk of multiple pregnancy during in vitro fertilization (IVF)
      treatment. Elective cryopreservation of all fresh embryos is also required in special
      circumstances where fresh transfer is undesirable, for example in cases where a high risk of
      ovarian hyperstimulation syndrome is anticipated. Fresh transfer is not advisable when serum
      progesterone level is elevated or hydrosalpinx is detected during ovarian stimulation.

      The availability of FETs would increase the likelihood of successful pregnancy from a single
      superovulation and oocyte retrieval cycle. It has been estimated that in modern IVF
      programmes which incorporates embryo cryopreservation, up to 42% of all conceptions could be
      derived from FET (Borini et al, 2008).

      Although the pregnancy rate in FET is comparable with stimulated IVF cycles, the optimal
      regimen to prepare the endometrium for implantation is not yet well proven. By a recent
      Cochrane review, there is no evidence to prove the use of one regimen in preference to
      another (Ghobara T 2008).

      Natural cycles (NC) are considered the best regimen as it is physiological, where natural
      conception occurs in. However, there are two most commonly employed methods to time the
      ovulation in natural cycles. One is to use ultrasound (USG) to monitor the follicular growth
      and endometrial thickness, with the use of human chorionic gonadotrophin (hCG) to trigger
      ovulation in the presence of a dominant follicle around 17-18mm in diameter. Another is to
      monitor the blood hormonal concentration to detect the luteinising hormone (LH) surge
      associated with natural ovulation. There is scarce information in this area as only one
      randomized controlled trial compared these two approaches. The authors aimed to recruit 240
      subjects, but the study was prematurely terminated as significant results were resulted in
      the first interim analysis when the sample size reached 124. The ongoing pregnancy rate was
      31.1% in the group with spontaneous LH surge and 14.3% in the hCG-induced group (Fatemi et
      al., 2010).

      The use of natural LH surge and hCG trigger in intrauterine insemination was compared too. A
      meta-analysis revealed a significantly higher clinical pregnancy rate in IUI cycles with
      natural LH surge than that with hCG trigger. However, the data from randomized controlled
      trial showed no significant difference. Also the data were contradictory when the analysis
      confined to a specific indication of subfertility (Kosmas et al., 2007). A cochrane review in
      2012 also suggested there was no evidence to advise that any regimen was better than another
      (Cantineau et al., 2012).

      This randomized controlled trial aims to compare the ongoing pregnancy rate of FET in
      spontaneous NC and hCG-induced NC. The hypothesis of this trial is that the ongoing pregnancy
      rate of FET is similar for spontaneous NC and hCG-induced NC. The advantage of hCG-induced NC
      is likely a reduction in the duration of monitoring for timing FET when compared with
      spontaneous NC.
    

Intervention name(s): Daily monitoring of LH and E2; hCG induced natural cycle; ultrasound
Intervention type(s): Procedure; Procedure; Device
Intervention description(s): ultrasound scanning would be carried out from 18 days before the expected period to confirm follicular growth, followed by daily blood monitoring of serum E2 and LH levels when the dominant follicle reaches 13-14mm in diameter. Ultrasound scanning can be arranged accordingly if the leading follicle remains less than 10mm in diameter. 5 ml of blood would be taken daily. LH surge is defined as the LH level being double of the average of the previous three days and higher than 20 IU/L. Ultrasound examination will be performed on the next day after the LH surge to measure the endometrial thickness. The transfer will be scheduled three or four days after the LH surge (for cleavage stage embryos) or six days after LH surge (for blastocyst transfer).; ultrasound monitoring would be started from 18 days before the expected period to monitor follicular growth, followed by USG every 2-3 days. hCG, 5,000-10,000 IU will be given when the leading follicle is >/= 17 mm and the endometrium measures >/=8 mm. Serum E2, LH and progesterone levels will be measured on the day of hCG. Embryo transfer would be scheduled on the fourth or fifth days after hCG injection (for cleavage stage embryos) or seventh days (for blastocyst transfer).
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: Frozen-thawed embryo transfer; natural cycle; spontaneous ovulation; hCG induced natural cycles