Study compares Pregnancy outcomes of fresh with cryopreserved-thawed embryo transfer
The use of cryopreserved donor oocytes in the United States
has been steadily increasing. One question that remains unanswered about
cryopreserved donor oocytes is whether there is a difference in pregnancy
outcomes among patients who use a fresh embryo transfer (ET) compared with
patients who cryopreserve the resulting embryo, followed later by a frozen ET.
Given the widespread use of frozen donor oocytes, determining whether an
association exists between either fresh or cryopreserved-thawed ET and the
resulting pregnancy outcome is imperative. Therefore, this study by Lauren
Barrison et al evaluated pregnancy outcomes among frozen donor oocyte cycles,
comparing fresh ET with cryopreserved-thawed ET.
This retrospective cohort study examined donor oocyte thaw
cycles using cryopreserved oocytes from Donor Egg Bank USA between 2016 and
2021. The study received institutional review board approval. Donor Egg Bank’s
standardized protocols were followed for donor screening, donor stimulation,
oocyte retrieval, oocyte vitrification, and oocyte shipping. Authors included
donor cycles with oocyte lots that were received by 2 different recipients,
with one undergoing fresh blastocyst transfer and one undergoing
cryopreservedthawed blastocyst transfer. The primary outcome was an ongoing
pregnancy, defined as a viable intrauterine pregnancy at the time of referral
to an obstetrician at approximately 8 weeks of gestation. Secondary outcomes
included additional pregnancy and embryonic development outcomes
A total of 1,210 recipient cycles of cryopreserved donor
oocytes were included (605 underwent fresh ET, 605 underwent
cryopreserved-thawed ET). The distribution for the year of oocyte thawing
between the fresh and frozen ET groups was distributed similarly for both
groups. The 2 groups were identical in regard to donor characteristics given
the sibling oocyte study design (mean age 25.5 years, mean body mass index 23.0
kg/m2 , mean antimullerian hormone level 5.9 ng/mL, mean antral follicle count
28.3). The recipients in the 2 groups were similar in age (mean age: 42.2 vs.
42.0 years). Surgically retrieved sperm was used by 2.8% of the fresh ET group
and 1.3% of the cryopreserved-thawed ET group.
There was no statistically significant difference in the
ongoing pregnancy rate between the fresh vs. cryopreserved-thawed ET groups
(51.2% vs. 49.6%; relative risk 0.97 [95% confidence interval, 0.83–1.14]).
Secondary pregnancy outcomes were also similar between the 2 groups.
Prior studies with mixed findings focused on comparing the
use of fresh vs. cryopreserved donor oocytes in fresh ET cycles or comparing
fresh vs. cryopreserved-thawed ET using fresh donor oocytes. Many patients use
cryopreserved donor oocytes because of their greater availability and access,
shorter time to treatment, and greater ease of cycle synchronization.
This study specifically addressed cryopreserved donor
oocytes and the potential impact of a second ‘‘freeze-thaw’’ on these gametes.
The retrospective study design restricts analysis to data
previously collected; the Donor Egg Bank’s data set did not include additional
recipient demographic information or transfer cycle characteristics, which
limits the ability to account for these potential confounders and the
generalizability of the findings. In conclusion, among patients using frozen
donor oocytes, pregnancy outcomes per donor oocyte thaw cycle were comparable
between recipients undergoing fresh ET compared with recipients using sibling
oocytes undergoing cryopreserved-thawed ET. On the basis of these findings,
patients using cryopreserved donor oocytes should not be deterred from subsequent
embryo cryopreservation.
Source: Lauren Barrison, M.D.a Melissa Stratton, B.A.b Wayne
Caswell, M.S; VOL. 122 NO. 3 /FertilitySterilty
https://doi.org/10.1016/j.fertnstert.2024.04.027
