Studies on the use of hCG in natural frozen embryo transfer (nFET) are uncommon. This recent study, published in March 2020 in the Journal of Assisted Reproduction and Genetics, is the first to use intramuscular human chorionic gonadotropin (hCG) and vaginal progesterone with natural frozen embryo transfer (nFET).

Of note, this study focused on natural cycle frozen embryo transfers - the women did not take hormonal drugs to prepare for the embryo transfer. In women who have normal hormone cycles with menstruation, two large studies from Spain and from China have recently shown that a natural cycle before transfer leads to higher rates of embryo implantation to the endometrium.

Study Background

WHAT

• Adding one injection of hCG to vaginal progesterone in nFET —-> does this increase rates of ongoing pregnancy?

WHY

• Increased progesterone and estrogen coming from corpus luteum

• Better outcomes, per the reproductive endocrinologist / third author

WHERE

• Center for Reproductive Medicine, Weill Cornell Medical Center, New York City

WHEN

• January 2017 - December 2018

WHO

Female Inclusion Criteria:

• Primary infertility (PCOS, endometriosis, recurrent miscarriage, low ovarian reserve, etc.)

• Amenable to genetic testing for least one euploid embryo via PGT-A

• Hormonally capable of utilizing nFET

Female Exclusion Criteria:

• Taking estrogen or progesterone medications before implantation

• History of uterine factor infertility

• Tubal disease requiring surgery

HOW

Embryos:

• Day 0: intracytoplasmic sperm injection (ICSI) to eliminate risk of sperm DNA contamination

• Day 5-6: biopsy and confirmation of euploid (normal chromosome) status by PGT-A

  • Graded blastocysts as excellent, good, average, and poor

  • Highest quality embryo selected for transfer

• Day 5-6: vitrification (rapid freezing)

Female patients:

1. Ovarian hyperstimulation

• Pre-treatment for cycle timing with Climara estrogen patches or Ortho-Novum birth control pills “in some cases” (# of patients not stated)

• Stimulation with gonadotropins (varying doses of Menopur, Gonal-F, and/or Follistim)

• Pituitary suppression with GnRH-antagonists (Cetrotide 0.25 mg or Ganirelix 0.25 mg)

• Down regulation, aka prevention of premature ovulation, with GnRH-agonist Lupron “less commonly” (# of patients not stated)

2. Follicular maturation trigger

• In general, used hCG as Novarel, Pregnyl, or the (now discontinued) Profasi

• For patients at risk of OHSS

  • Lupron 4 mg

  • Lupron 4 mg + 1500 IU hCG

3. Oocyte retrival —-> ICSI —-> Embryo biopsy and selection

4. Before embryo transfer, female patients were split into Group A or Group B based on physician preference (not randomized).

• Group A = one injection of hCG (2,500 - 10,000 IU) one day after LH surge

  • Eight women received 2,500 IU; 105 women received 3,300, twenty-six women received 5000 IU, and seven women received 10,000 IU

  • Higher BMI = higher hCG doses

• Group B = no hCG

5. Transfer of one PGT-A embryo (timing based on date of embryo vitrification) into each patient.

6. The night after embryo transfer, all patients started vaginal progesterone.

7. Ten days after transfer, both groups were tested for estrogen (E2), progesterone (P4), and hCG levels.

• If pregnancy was +, the woman returned 48h later for another hCG test

• If pregnancy still +, the woman returned at 5.5 weeks to confirm pregnancy was intra-uterine (correct position)

  Statistics (for the uber curious)

“Student’s t test was used for parametric data. Categorical variables were compared by Chi-square and Fisher’s exact tests. Odds ratios (OR) with 95% confidence intervals (CI) were calculated and adjusted for patient age at time of transfer, embryo quality as assessed by blastocyst grade, BMI, gravidity, parity, and peak endometrial thickness. P < 0.05 was considered statistically significant.”

Results

• 529 nFET cycles included

  • 146 in Group A (hCG boost)

  • 383 in Group B (no boost)

  • At baseline, Group B had statistically higher gravidity and parity as well as thicker peak endometrial thickness - per authors, not clinically significant

  • Almost reached statistical significance (p = 0.06) for # of average quality embryos (46% in Group A vs. 54% in Group B)

• Ongoing pregnancy rates higher in Group A (69.9%) vs. Group B (57.4%), p = 0.0119; OR 1.717 (95% CI 1.149–2.600); aOR 1.724 (95% CI 1.13–2.65)

• No difference between Group A and Group B for first trimester pregnancy loss or for biochemical pregnancy

• Higher embryo quality associated with better pregnancy outcomes (only statistically significant for average embryos due to small sample sizes)

• No relationship found between the specific dose of hCG booster and ongoing pregnancy rate (p =0.5096)

• Results different than those found in prior studies, Mandani et al. and Lee et al. , where hCG as luteal support did NOT improve ongoing pregnancy rates

  • Mandani et al. used hCG 2500 IU every three days, no progesterone given

  • Lee et al. used hCG 1500 IU the same day as embryo transfer + 6 days later, no progesterone given

    Key Takeaways

Authors Thoughts

• Results make sense in context of testing embryos using PGT-A, unlike previous hCG booster studies.

• Boosting with hCG during IVF may mimic how hCG works during natural fertilization.

• Strengths of study were incorporating women of all age ranges and infertility diagnoses as well as testing then excluding embryos with abnormal chromosomes.

• Variable (non-standardized) hCG booster doses were a notable study weakness.

This Pharmacist’s Thoughts

• This study produced more questions than answers.

  • Some but not all patients were given Climara, birth control, and/or Lupron in the study. Did these medications impact the quality of embryos?

  • Requiring the use of ICSI to produce embryos seems like a limitation - is ICSI really required to produce the same results?

  • What would the results look like if hCG doses had been standardized based on BMI and/or infertility diagnosis?

  • There was almost a statistically higher number of average embryos in Group B - was this higher number clinically significant? If yes, it may have contributed to the poorer results in Group B.

• Given the variability in dosing from all of the medications used, especially hCG, it doesn’t seem reasonable to expect the results to be easily replicated.

• Having patients randomized to hCG, at one specific dose, would have increased the objectivity and lowered the bias associated with provider-specified selection for hCG.

• This study contributes to the knowledge base of understanding the utility of hCG in nFET transfer, but more studies are needed

Resources

Behjati S, Tarpey PS. What is next generation sequencing?. Arch Dis Child Educ Pract Ed. 2013;98(6):236-238. doi:10.1136/archdischild-2013-304340

Cardenas Armas DF, Peñarrubia J, Goday A, et al. Frozen-thawed blastocyst transfer in natural cycle increase implantation rates compared artificial cycle. Gynecol Endocrinol. 2019;35(10):873-877. doi:10.1080/09513590.2019.1600668

Feldman B, Aizer A, Brengauz M, et al. Pre-implantation genetic diagnosis-should we use ICSI for all?. J Assist Reprod Genet. 2017;34(9):1179-1183. doi:10.1007/s10815-017-0966-7

Lee VCY, Li RHW, Yeung WSB, Pak Chung HO, Ng EHY. A randomized double-blinded controlled trial of hCG as luteal phase support in natural cycle frozen embryo transfer. Hum Reprod. 2017;32(5):1130-1137. doi:10.1093/humrep/dex049

Liu X, Shi W, Shi J. Natural cycle frozen-thawed embryo transfer in young women with regular menstrual cycles increases the live-birth rates compared with hormone replacement treatment: a retrospective cohort study. Fertil Steril. 2020;113(4):811-817. doi:10.1016/j.fertnstert.2019.11.023

Madani T, Ramezanali F, Yahyaei A, Hasani F, Bagheri Lankarani N, Mohammadi Yeganeh L. Live birth rates after different endometrial preparation methods in frozen cleavage-stage embryo transfer cycles: a randomized controlled trial. Arch Gynecol Obstet. 2019;299(4):1185-1191. doi:10.1007/s00404-019-05062-7

Reichman DE, Stewart CR, Rosenwaks Z. Natural frozen embryo transfer with hCG booster leads to improved cycle outcomes: a retrospective cohort study. J Assist Reprod Genet. 2020;37(5):1177-1182. doi:10.1007/s10815-020-01740-7