BACKGROUND AND PURPOSE:

• Data suggests that a freeze-all strategy for embryo transfer may have benefit in the context of PCOS
  • Data for normal cycles are conflicting
• There is potential benefit to a freezing strategy because it avoids the risk of hyperstimulation – GnRH agonist can be used for triggering final maturation
• Stormlund et al. (BMJ, 2020) assessed pregnancy rate using a freeze-all strategy with GnRH agonist triggering vs fresh strategy with conventional hCG triggering

METHODS:

• Multicenter, randomized controlled superiority trial
• Participants
  • 18 to 39 years
  • Regular menses
  • First, second, or third IVF treatment cycle
• Interventions
  • Freeze-all group (elective freezing of all embryos): GnRH agonist triggering and single frozen-thawed blastocyst transfer in a subsequent modified natural cycle
  • Fresh transfer group: hCG triggering and single blastocyst transfer in the fresh cycle
• Study design
  • Randomization on cycle day 2 or 3
  • Analysis was performed as intention-to-treat
• Primary outcome
  • Ongoing pregnancy rate definition:  Detectable fetal heart beat after eight weeks of gestation
• Secondary outcomes
  • Live birth rate
  • Positive hCG rate
  • Time to pregnancy
  • Pregnancy related complication (obstetric and neonatal)

RESULTS:

• 453 women were included
  • Freeze-all: 223 women
  • Fresh: 230 women
• Ongoing pregnancy rate did not differ significantly between the freeze-all and fresh transfer groups (P=0.76)
  • Freeze-all: 27.8%
  • Fresh: 29.6%
  • Risk ratio (RR) 0.98 (95% CI, 0.87 to 1.10)
• There was no significant difference in the live birth rate (P=0.83)
  • Freeze-all: 27.4% (61 women)
  • Fresh: 28.7% (66 women)
  • RR 0.98 (95% CI, 0.87 to 1.10)
• There were no significant differences in positive hCG rate or pregnancy loss
• There were no significant differences between the 2 groups for the following
  • Severe ovarian hyperstimulation syndrome
  • Obstetric, and neonatal complications
• Higher mean birth weight associated with frozen transfer (P<0.001)
  • Freeze-all: 3586g
  • Fresh: 3117g
• Increased risk of prematurity associated with fresh transfer (P=0.01)
  • Freeze-all: 0
  • Fresh: 11.1%
• Time to pregnancy was longer in the freeze-all group (P<0.001)
  • Freeze-all: 86 days
  • Fresh: 28 days

CONCLUSION:

• A freeze-all strategy, with GnRH agonist triggering for final oocyte maturation, did not improve pregnancy or live birth rates, compared to a fresh transfer strategy, in women with regular menstrual cycles
• The authors state

…fresh embryo transfer should be used as the gold standard if no apparent treatment advantage or immediate risk of ovarian hyperstimulation syndrome is present because it is vital for patients not to postpone pregnancy

Learn More – Primary Sources:

Freeze-all versus fresh blastocyst transfer strategy during in vitro fertilisation in women with regular menstrual cycles: multicentre randomised controlled trial

Related ObG Topics:

Frozen or Fresh Embryos for IVF Transfer?

Embolism Following IVF: Does Fresh or Frozen-Thawed Transfer Matter?

ASRM guidance: ART and recommended number of embryos to transfer