Fresh, frozen embryo transfers yield similar pregnancy rates

Pregnancy rates for fresh embryo transfer during in vitro fertilization were similar to the freeze-all strategy, and time to pregnancy was significantly longer with the freeze-all approach, according to a study published in BMJ.

“New randomized controlled trials have reported conflicting results in reproductive outcomes after the freeze-all strategy compared with fresh transfer in women who have regular menstrual cycles,” Sacha Stormlund, MD, PhD, from the Fertility Clinic in the department of obstetrics and gynecology at Hvidovre University Hospital in Denmark, and colleagues wrote. “However, the concept of a freeze-all strategy that uses gonadotropin releasing hormone agonist triggering has not been tested.”

Stormlund and colleagues conducted a randomized controlled superiority trial to evaluate freeze-all and fresh transfer strategies at fertility clinics in eight hospitals in Sweden, Denmark and Spain.

The trial included 460 women aged 18 years to 39 years who had regular menstrual cycles and were beginning their first, second or third treatment cycle of IVF intracytoplasmic sperm injection due to tubal, uterine, male or unexplained infertility.

Before ovarian stimulation, women were randomly assigned one of two treatment strategies. In the freeze-all strategy, women received gonadotropin release hormones to trigger egg maturity and later a single frozen-thawed blastocyst transfer. Using the fresh transfer strategy, women received chorionic gonadotropin to trigger egg maturity, and then underwent fresh blastocyst transfers.

If women who were assigned to the fresh transfer group had more than 18 follicles larger than a mean diameter of 11 mm on the day of ovulation, they received gonadotropin releasing hormone agonist to prevent ovarian hyperstimulation syndrome. They subsequently had their first blastocyst transfer postponed and instead underwent a modified natural frozen transfer cycle.

Researchers conducted human chronic gonadotropin tests 11 days after blastocyst transfer and transvaginal ultrasounds 3 or 4 weeks later if the tests were positive to confirm participants’ ongoing pregnancy.

Stormlund and colleagues determined that the ongoing pregnancy rate did not differ significantly between the groups — 27.8% in the freeze-all group and 29.6% in the fresh transfer group (RR = 0.98; 95% CI, 0.87-1.1).

They also found no significant difference in the rate of live births between the groups, with 27.4% in the freeze-all group and 28.7% in the fresh transfer (RR = 0.98, 95% CI, 0.87-1.1).

Researchers did not identify significant differences between groups for positive human chorionic gonadotropin or loss of pregnancy.

The median time to pregnancy was longer in the freeze-all group at 86 days (IQR = 77-107) compared with the fresh transfer group 28 (IQR = 27-30), researchers found.

“In women with regular menstrual cycles, a freeze-all strategy with gonadotropin releasing hormone agonist triggering for final oocyte maturation did not result in higher ongoing pregnancy and live birth rates than a fresh transfer strategy,” Stormlund and colleagues wrote.

Because time to pregnancy was longer in the freeze-all group, the researchers suggested fresh embryo transfer should be used as the “gold standard” if there is no apparent treatment advantage or an immediate risk for ovarian hyperstimulation syndrome, since it is critical for these patients not to postpone pregnancy.