Twice vitrification-warming procedures has no effect on frozen-thawed embryo transfer outcomes

Abstract Background To evaluate the frozen-thawed embryo transfer (FET) outcomes of repeated cryopreservation by vitrification of blastocysts derived from vitrified-warmed day3 embryos in patients who experienced implantation failure previously. Methods We retrospect the files of patients who underwent single frozen-thawed blastocyst transfer cycles in our reproductive medical center from January 2013 to December 2019. 127 patients transfer of vitrified-warmed blastocysts derived from vitrified-warmed day3 embryos were defined as twice-cryopreserved group. 1567 patients who transfer blastocysts that had experienced once vitrified-warmed were used as once-cryopreserved group. None of them was pregnant at the previous FET. The outcomes were compared between two groups after a 1:1 propensity score matching (PSM). Results The clinical pregnancy rate was 52.76%, live birth rate was 43.31% in twice-cryopreserved group. After PSM,108 pairs of patients were generated for comparison. The clinical pregnancy rate, live birth rate or miscarriage rate was not significantly different between two groups. Logistic regression analysis indicated that double vitrification-warming procedures did not affect FET outcomes in terms of clinical pregnancy rate (OR 0.83, 95%CI 0.47-1.42), live birth rate (OR 0.93, 95%CI 0.54-1.59), miscarriage rate (OR 0.72 95%CI 0.28-1.85). Furthermore, the pregnancy complications rate, gestational age or neonatal abnormalities rate between two groups was also comparable, while twice vitrification-warming procedures might increase the macrosomia rate (19.6% vs. 6.3%, P = 0.05). Conclusion Transfer of double vitrified-warmed embryo at cleavage stage and subsequent blastocyst stage did not affect live birth rate and neonatal abnormalities rate, but there was a tendency to increase macrosomia rate, which needs further investigation.

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Does estradiol orally and vaginally administered together impact live birth and neonatal outcomes in artificial frozen-thawed embryo transfer cycles: a retrospective cohort study

10.21203/rs.3.rs-42796/v2 ◽

2020 ◽

Author(s):

Yuan Liu ◽

Yixia Yang ◽

Jian Sun ◽

Xinting Zhou ◽

Yanmei Hu ◽

...

Keyword(s):

Pregnancy Rate ◽

Embryo Transfer ◽

Live Birth ◽

Birth Rate ◽

Live Birth Rate ◽

Clinical Pregnancy ◽

Neonatal Outcomes ◽

Serum Estradiol ◽

Frozen Thawed Embryo Transfer ◽

Thawed Embryo Transfer

Abstract Background: Previous studies have demonstrated that newborns from fresh embryo transfer have higher risk of small for gestation (SGA) rate than those from frozen-thawed embryo transfer (FET). It is suggested that supraphysiologic serum estradiol in controlled ovarian stimulation (COS) is one of reasons. Our study aims to investigate whether exogenous estradiol delivered regimens have an impact on live birth rate and neonatal outcomes in hormone replacement (HRT)-FET cycles. Methods: This was a retrospective study involving patients undergoing their first FET with HRT endometrium preparation followed by the transfer of two cleavage-staged embryos, comparing estradiol administered orally and vaginally (OVE group) versus estradiol administered orally (OE group) from January 2015 to December 2018 at our center. A total of 792 patients fulfilled the criteria, including 228 live birth singletons. The live birth rate was the primary outcome measure. Secondary outcome measures included clinical pregnancy rate, singleton birthweight, large for gestational age (LGA) rate, SGA rate, preterm delivery rate. Results: Patients in OVE group achieved higher serum estradiol level with more days of estradiol treatment. No difference in live birth (Adjusted OR 1.327; 95%CI 0.982, 1.794, p = 0.066) and clinical pregnancy rate (Adjusted OR 1.278; 95%CI 0.937, 1.743, p = 0.121) was found between OVE and OE groups. Estradiol route did not affect singletons birth weight (β = -30.962, SE = 68.723, p = 0.653), the odds of LGA (Adjusted OR 1.165; 95%CI 0.545, 2.490, p = 0.694), the odds of SGA (Adjusted OR 0.569; 95%CI 0.096, 3.369, p = 0.535) or the preterm delivery (Adjusted OR 0.969; 95%CI 0.292, 3.214, p = 0.959). Conclusion: Estrogen taken orally and vaginally together did not change live birth rate and singleton neonatal outcomes compared to estrogen taken orally, but was accompanied with relative higher serum E2 level and potential maternal undesirable risks.

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Impact of Luteinized Unruptured Follicles on Clinical Outcomes of Natural Cycles for Frozen/Thawed Blastocyst Transfer

Frontiers in Endocrinology ◽

10.3389/fendo.2021.738005 ◽

2021 ◽

Vol 12 ◽

Author(s):

Song Li ◽

Lokwan Liu ◽

Tian Meng ◽

Benyu Miao ◽

Mingna Sun ◽

...

Keyword(s):

Pregnancy Rate ◽

Clinical Outcomes ◽

Live Birth ◽

Birth Rate ◽

Live Birth Rate ◽

Clinical Pregnancy ◽

Clinical Pregnancy Rate ◽

Frozen Thawed Embryo Transfer ◽

Natural Cycles ◽

Thawed Embryo Transfer

ObjectiveTo investigate the impact of luteinized unruptured follicles (LUF) on clinical outcomes of frozen/thawed embryo transfer (FET) of blastocysts.MethodsIn this retrospective cohort study, 2,192 patients who had undergone blastocyst FET treatment with natural cycles from October 2014 to September 2017 were included. Using propensity score matching, 177 patients diagnosed with LUF (LUF group) were matched with 354 ovulating patients (ovulation group). The LUF group was further stratified by the average LH peak level of 30 IU/L. Clinical pregnancy rate and live birth rate were retrospectively analyzed between the LUF and ovulation groups, as well as between LUF subgroups.ResultsAfter propensity score matching, general characteristics were similar in the LUF and ovulation groups. Clinical pregnancy rate in the LUF group was significantly lower than that in the ovulation group (47.46 vs. 58.76%, respectively, adjusted P = 0.01, OR 0.60, 95% CI 0.42–0.87). However, no significant difference was detected in live birth rate, although it was lower in the LUF group (43.50 vs. 50.00%, adjusted P = 0.19, OR 0.76, 95% CI 0.51–1.14). In the LUF subgroup analysis, both clinical pregnancy rate (43.02 vs. 62.30%, adjusted P = 0.02, OR 0.45, 95% CI 0.23–0.87) and live birth rate (37.21 vs. 59.02%, adjusted P = 0.01, OR 0.40, 95% CI 0.20–0.78) in the LH <30 IU/L subgroup were significantly lower than those in the LH ≥30 IU/L subgroup.ConclusionLUF negatively affected clinical outcomes of frozen/thawed embryo transfer of blastocysts, particularly when the LH surge was inadequate.

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Does Estradiol Orally and Vaginally Administered Together Impact Live Birth and Neonatal Outcome in Artificial Frozen-thawed Embryo Transfer Cycles: A Retrospective Cohort Study

10.21203/rs.3.rs-42796/v1 ◽

2020 ◽

Author(s):

Yuan Liu ◽

Yixia Yang ◽

Xinting Zhou ◽

Yanmei Hu ◽

Yu Wu

Keyword(s):

Pregnancy Rate ◽

Preterm Delivery ◽

Embryo Transfer ◽

Live Birth ◽

Clinical Pregnancy ◽

Clinical Pregnancy Rate ◽

Delivery Rate ◽

Serum Estradiol ◽

Frozen Thawed Embryo Transfer ◽

Thawed Embryo Transfer

Abstract Background: Previous studies have demonstrated that newborns from fresh embryo transfer are with higher risk of small for gestation (SGA) rate than those from frozen-thawed embryo transfer (FET). It is suggested that supraphysiologic serum estradiol in controlled ovarian stimulation (COS)is one of reasons. Out study aims to investigate whether exogenous estradiol delivered regimens have an impact on live birth rate and singleton birthweight in hormone replacement (HRT)-FET cycles.Methods:This retrospective study involved patients undergoing their first FET with HRT endometrium preparation followed by two cleavage-staged embryos transfer, comparing orally and vaginal estradiol tablets (OVE) group versus oral estradiol tablets (OE) group from January 2015 to December 2018 at our center. A total of 792 patients fulfilled the criteria, including 282 live birth singletons. Live birth was the primary outcome. Secondary outcome included clinical pregnancy rate, singleton birthweight, large for gestational age (LGA) rate, SGA rate, preterm delivery rate. Results:Patients in OVE group achieved higher serum estradiol level with more days of estradiol treatment. No difference in live birth (Adjusted OR 1.327; 95%CI 0.982, 1.794, p=0.066) and clinical pregnancy rate (Adjusted OR 1.278; 95%CI 0.937, 1.743, p=0.121) was found between OVE and OE groups. Estradiol route did not affect birth weight (β=-30.962, SE=68.723, p=0.653), the odds of LGA (Adjusted OR 1.165; 95%CI 0.545, 2.490, p=0.694), the odds of SGA (Adjusted OR 0.569; 95%CI 0.096, 3.369, p=0.535) or the preterm delivery rate (Adjusted OR 0.969; 95%CI 0.292, 3.214, p=0.959).Conclusion:Estrogen orally and vaginally together did not have an impact on clinical outcomes and singleton birthweight compared to estrogen orally taken, but was accompanied with relative higher serum E2 level and potential maternal undesirable risks.

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Dydrogesterone is Superior as Luteal Phase Support in selected Previously Failed In-Vitro Fertilisation and Embryo Transfer Patients

Journal of Gynecology & Reproductive Medicine ◽

10.33140/jgrm.05.01.08 ◽

2021 ◽

Vol 5 (1) ◽

Keyword(s):

Pregnancy Rate ◽

Embryo Transfer ◽

Birth Rate ◽

Live Birth Rate ◽

Clinical Pregnancy ◽

Clinical Pregnancy Rate ◽

P Value ◽

Miscarriage Rate ◽

Secretory Endometrium ◽

Micronized Progesterone

Different forms of exogenous progesterone have been seen to play a very important role in endometrial maturity. Implantation failure appears to be a significant factor in Assisted reproductive technique (ART) procedures. Even a mature endometrium becomes non-receptive, preventing implantation or rejection of implanted embryo in early months of pregnancy. Hence natural micronized progesterone (NMP) and dydrogesterone have been used since decades to improve endometrial maturity and receptivity. The aim of this study was to investigate causes of failed implantation inspite of uneventful Grade I embryo transfer in ART procedure and the role of natural micronized progesterone (NMP) and dydrogesterone for endometrial maturation. 80 women aged range between 25-40 yr old who visited Department of Reproductive Medicine at Calcutta Fertility Mission, over a period of 24 months (January 2017 to December 2019), satisfying the inclusion criteria, were enrolled in this retrospective observational study. Endometrial aspirate histopathology was done during the secretory phase. They were treated with natural micronized progesterone (NMP) or oral dydrogesterone and results of endometrial changes, clinical pregnancy rate, live birth rate and miscarriage rate were statistically analysed. 26.25% and 29.6% of women were seen to have mid-secretory changes of the endometrium after being treated with NMP in one cycle and dydrogesterone in the subsequent cycle, respectively. 62.71% of women had shown early-secretory changes with dydrogesterone which was statistically significant compared to those treated with NMP (p value=0.006).8.5% of these women showed persistent non-secretory endometrium with either of these medications. The Clinical Pregnancy Rate (CPR) was 38.1% and 47% in the group of patients who were treated with NMP and dydrogesterone respectively. Though pregnancy rate was slightly higher in dydrogesterone group, it was not statistically significant (p value = 0.578). 28.5% and 41% women had live births and 9.5% and 5.8% of them had miscarriage in NMP and dydrogesterone group, respectively, though our data appears to be statistically not significant (p value –0.415) (p value – 0.679). In our study 26.25% women had mid-secretory endometrium after treatment with NMP. 29.6% and 62.71% of these women who had non-secretory or early secretory endometrial changes on treatment with intravaginal NMP, showed endometrial mid-secretory and early-secretory changes respectively, on treatment with dydrogesterone, which implies that oral dydrogesterone is superior to NMP when administered for endometrial maturation in selected patients. Clinical pregnancy rate, live birth rate or miscarriage rate were similar with either NMP or dydrogesterone.

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The Effect of Assisted Hatching on Live Birth Rate Following Fresh Embryo Transfer in Advanced Maternal Age

Reproductive Sciences ◽

10.1177/1933719118799192 ◽

2018 ◽

Vol 26 (6) ◽

pp. 806-811 ◽

Cited By ~ 1

Author(s):

Samer Tannus ◽

Yoni Cohen ◽

Sara Henderson ◽

Weon-Young Son ◽

Togas Tulandi

Keyword(s):

Pregnancy Rate ◽

Embryo Transfer ◽

Live Birth ◽

Maternal Age ◽

Birth Rate ◽

Live Birth Rate ◽

Advanced Maternal Age ◽

Clinical Pregnancy ◽

Clinical Pregnancy Rate ◽

Assisted Hatching

Objective: Assisted hatching (AH) was introduced 3 decades ago as an adjunct method to in vitro fertilization (IVF) and embryo transfer (ET) to improve embryo implantation rate. Limited data are available on the effect of AH on live birth rate (LBR) in advanced maternal age. The objective of this study is to investigate the effect of AH on LBR in women aged 40 years and older. Materials and Methods: A retrospective study conducted at a single academic reproductive center. Women aged ≥40 years, who were undergoing their first IVF cycle were included. Laser-assisted hatching was the method used for AH and single or double embryos were transferred. Embryo transfer was performed at the cleavage or blastocyst stage. Separate analysis was performed on each ET stage. Live birth rate was the primary outcome. Results: A total of 892 patients were included. Of these, 681 women underwent cleavage ET and 211 underwent blastocyst ET. The clinical pregnancy rate in the entire group was 15.3% and the LBR was 10.2%. Baseline and cycle parameters between the AH group and the control group were comparable. Assisted hatching in the cleavage stage was associated with lower clinical pregnancy rate (odds ratio [OR], 0.52; confidence interval [CI], 0.31-0.86; P = .012) and lower LBR (OR, 0.36; CI, 0.19-0.68; P = .001). Assisted hatching did not have any effect on outcomes in blastocyst ET. Conclusion: Assisted hatching does not improve the reproductive outcomes in advanced maternal age. Performing routine AH for the sole indication of advanced maternal age is not clinically justified.

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Effect of Endometrium Thickness on Clinical Outcomes in Luteal Phase Short-Acting GnRH-a Long Protocol and GnRH-Ant Protocol

Frontiers in Endocrinology ◽

10.3389/fendo.2021.578783 ◽

2021 ◽

Vol 12 ◽

Author(s):

Jie Zhang ◽

Yi-Fei Sun ◽

Yue-Ming Xu ◽

Bao-jun Shi ◽

Yan Han ◽

...

Keyword(s):

Pregnancy Rate ◽

Clinical Outcomes ◽

Live Birth ◽

Birth Rate ◽

Endometrial Thickness ◽

Live Birth Rate ◽

Clinical Pregnancy ◽

Clinical Pregnancy Rate ◽

Miscarriage Rate ◽

Long Protocol

ObjectiveTo investigate the factors that influence luteal phase short-acting gonadotropin-releasing hormone agonist (GnRH-a) long protocol and GnRH-antagonist (GnRH-ant) protocol on pregnancy outcome and quantify the influence. About the statistical analysis, it is not correct for the number of gravidities.MethodsInfertile patients (n = 4,631) with fresh in-vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) and embryo transfer were divided into GnRH-a long protocol (n =3,104) and GnRH-ant (n =1,527) protocol groups and subgroups G1 (EMT ≤7mm), G2 (7 mm <EMT ≤10 mm), and G3 (EMT >10 mm) according to EMT on the trigger day. The data were analyzed.ResultsThe GnRH-ant and the GnRH-a long protocols had comparable clinical outcomes in the clinical pregnancy, live birth, and miscarriage rate after propensity score matching. In the medium endometrial thickness of 7–10 mm, the clinical pregnancy rate (61.81 vs 55.58%, P < 0.05) and miscarriage rate (19.43 vs 12.83%, P < 0.05) of the GnRH-ant regime were significantly higher than those of the GnRH-a regime. The EMT threshold for clinical pregnancy rate in the GnRH-ant group was 12 mm, with the maximal clinical pregnancy rate of less than 75% and the maximal live birth rate of 70%. In the GnRH-a long protocol, the optimal range of EMT was >10 mm for the clinical pregnancy rate and >9.5 mm for the live birth rate for favorable clinical outcomes, and the clinical pregnancy and live birth rates increased linearly with increase of EMT. In the GnRH-ant protocol, the EMT thresholds were 9–6 mm for the clinical pregnancy rate and 9.5–15.5 mm for the live birth rate.ConclusionsThe GnRH-ant protocol has better clinical pregnancy outcomes when the endometrial thickness is in the medium thickness range of 7–10 mm. The optimal threshold interval for better clinical pregnancy outcomes of the GnRH-ant protocol is significantly narrower than that of the GnRH-a protocol. When the endometrial thickness exceeds 12 mm, the clinical pregnancy rate and live birth rate of the GnRH-ant protocol show a significant downward trend, probably indicating some negative effects of GnRH-ant on the endometrial receptivity to cause a decrease of the clinical pregnancy rate and live birth rate if the endometrial thickness exceeds 12 mm.

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Outcome of mock embryo transfer before the first IVF cycle: A randomized control trial

International Journal of Reproductive BioMedicine ◽

10.18502/ijrm.v13i11.7962 ◽

2020 ◽

Author(s):

Amol Borkar ◽

Amit Shah ◽

Anil Gudi ◽

Roy Homburg

Keyword(s):

Pregnancy Rate ◽

Embryo Transfer ◽

Live Birth ◽

Birth Rate ◽

Multiple Pregnancy ◽

Live Birth Rate ◽

Clinical Pregnancy ◽

Clinical Pregnancy Rate ◽

Secondary Outcome ◽

Significant Difference

Background: There is a lack of agreement among fertility specialists with regard to the routine use of mock embryo transfer (MET) before each in vitro fertilization (IVF) treatment cycle. While MET may be beneficial with previous difficult embryo transfer cases, its routine use before first IVF cycle has not been evaluated. Objective: To find out the effect of MET before the first IVF cycle on clinical pregnancy rate. Materials and Methods: This is a single-centre randomized controlled trial with a balanced randomization (1:1), carried out between November 2015 and October 2017, with 200 subjects at Homerton university hospital, London, randomized into either MET or control. The primary outcome was clinical pregnancy rate (detection of heart activity on the ultrasound scan), the secondary outcome measures were live birth rate, miscarriage and multiple pregnancy rates, difficult ETs, rate of blood or mucus on the catheter tip. Results: No significant differences were observed in the baseline or cycle characteristics between the two groups. The clinical pregnancy rate was similar between the MET and control groups based on both intension to treat and per protocol analyses (p = 0.98, p = 0.92, respectively). Additionally, no significant difference was seen in the live birth rate in both groups on intension to treat and per protocol analyses (p = 0.67, p = 0.47), respectively. Conclusion: Our study concludes that MET prior to first IVF cycle may not improve the success rate in young women without risk factors for a difficult embryo transfer. Key words: IVF, Mock embryo transfer, Pregnancy outcomes, Live birth.

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Pretreatment with a GnRH agonist and hormone replacement treatment protocol could not improve live birth rate for PCOS women undergoing frozen-thawed embryo transfer cycles

BMC Pregnancy and Childbirth ◽

10.1186/s12884-021-04293-4 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Xitong Liu ◽

Juanzi Shi ◽

Haiyan Bai ◽

Wen Wen

Keyword(s):

Propensity Score ◽

Pregnancy Rate ◽

Embryo Transfer ◽

Live Birth ◽

Birth Rate ◽

Hormone Replacement ◽

Live Birth Rate ◽

Replacement Treatment ◽

Frozen Thawed Embryo Transfer ◽

Thawed Embryo Transfer

Abstract Background The ideal protocols of endometrial preparation for polycystic ovary syndrome (PCOS) patients are lacking and need further declaration. Our objective was to compare the clinical outcomes of frozen-thawed embryo transfer (FET) with and without pretreatment gonadotropin-releasing hormone agonist (GnRHa) in PCOS patients. Methods In this retrospective cohort study, we used propensity score matching (PSM) to compare the live birth rate between patients who underwent FET with hormone replacement treatment (HRT) and patients with GnRHa pretreatment (GnRHa + HRT). Patients using GnRHa + HRT (n = 514) were matched with 514 patients using HRT. Results The live birth rate was higher in the GnRHa + HRT group compared with the HRT group with no significant difference (60.12% vs 56.03%, p = 0.073). The clinical pregnancy rate (75.29% vs 70.62%), miscarriage rate (14.20% vs 13.81%) and ectopic pregnancy rate (0.39% vs 0.19%) were similar between the two groups. The preterm birth rate in GnRHa + HRT was higher than HRT (20.23% vs 13.04%). No difference was found in live birth between GnRHa +HRT and HRT before adjusting for covariates (crude OR 1.22, 95%CI, 0.99–1.51, p = 0.062) and after PSM (OR 1.47, 95%CI, 0.99–2.83, p = 0.068). In addition, there is a marginally difference after adjusting for covariates (aOR 1.56, 95%CI, 1.001–2.41, p = 0.048), this finding with p-value close to 0.05 represent insufficient empirical evidence. Similar results were obtained after propensity score matching in the entire cohort. Conclusions GnRHa pretreatment could not improve the live birth rate in women with PCOS.

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Comparison of IVF Outcomes between Minimal Stimulation and High-Dose Stimulation for Patients with Poor Ovarian Reserve

International Journal of Reproductive Medicine ◽

10.1155/2014/581451 ◽

2014 ◽

Vol 2014 ◽

pp. 1-5 ◽

Cited By ~ 15

Author(s):

Tal Lazer ◽

Shir Dar ◽

Ekaterina Shlush ◽

Basheer S. Al Kudmani ◽

Kevin Quach ◽

...

Keyword(s):

Pregnancy Rate ◽

Live Birth ◽

Ovarian Reserve ◽

Birth Rate ◽

Live Birth Rate ◽

Clinical Pregnancy ◽

Clinical Pregnancy Rate ◽

Poor Responders ◽

High Dose ◽

Poor Ovarian Reserve

We examined whether treatment with minimum-dose stimulation (MS) protocol enhances clinical pregnancy rates compared to high-dose stimulation (HS) protocol. A retrospective cohort study was performed comparing IVF and pregnancy outcomes between MS and HS gonadotropin-antagonist protocol for patients with poor ovarian reserve (POR). Inclusion criteria included patients with an anti-Müllerian hormone (AMH) ≤8 pmol/L and/or antral follicle count (AFC) ≤5 on days 2-3 of the cycle. Patients from 2008 exclusively had a HS protocol treatment, while patients in 2010 had treatment with a MS protocol exclusively. The MS protocol involved letrozole at 2.5 mg over 5 days, starting from day 2, overlapping with gonadotropins, starting from the third day of letrozole at 150 units daily. GnRH antagonist was introduced once one or more follicles reached 14 mm or larger. The HS group received gonadotropins (≥300 IU/day) throughout their antagonist cycle. Clinical pregnancy rate was significantly higher in the MS protocol compared to the HS protocol (P=0.007). Furthermore, the live birth rate was significantly higher in the MS group compare to the HS group (P=0.034). In conclusion, the MS IVF protocol is less expensive (lower gonadotropin dosage) and resulted in a higher clinical pregnancy rate and live birth rate than a HS protocol for poor responders.

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The effect of air bubble position on ART outcome in frozen-thawed blastocyst transfer

10.21203/rs.3.rs-1059586/v1 ◽

2021 ◽

Author(s):

Tingting Yang ◽

Bo Chen ◽

Xiaoyan Sun ◽

Qingyang Li ◽

Qiumei Li ◽

...

Keyword(s):

Pregnancy Rate ◽

Live Birth ◽

Birth Rate ◽

Live Birth Rate ◽

Clinical Pregnancy ◽

Clinical Pregnancy Rate ◽

Blastocyst Transfer ◽

Ultrasound Guided ◽

Air Bubble ◽

Art Outcome

Abstract Background So far, only few literatures have studied the relationship between blastocyst transfer position and ART outcomes, and the conclusions are still controversial. Our study is to evaluate the effect of air bubble position on ART outcome and to find the optimal embryo transfer position in frozen-thawed blastocyst transfer. Methods This study included a retrospective cohort analysis of 399 frozen-thawed single blastocyst transfers ultrasound-guided performed between June 1, 2017 and November 30, 2020. All of the women scheduled for frozen-thawed single blastocyst transfers ultrasound-guided. The primary outcome is clinical pregnancy rate and the secondary outcome is live birth rate. Statistical analyses were conducted using One-way Anova, Kruscal Whallis H test, chi-square test and Smooth curve fitting. Results When BFD was less than 19 mm, there was no significant change in clinical pregnancy rate as BFD increased (OR = 0.95, 95% CI: 0.89 to 1.02, P = 0.1373); when BFD was more than 19 mm, the clinical pregnancy rate decreased by 16% for every 1 mm increase in BFD (OR = 0.84, 95% CI: 0.72 to 0.98, P = 0.0363). The effect of BFD on live birth rate were similar to that on clinical pregnancy rate, the inflection point was 19mm, when BFD was more than 19 mm, the live birth rate decreases by 58% for every 1 mm increase in BFD (OR = 0.42, 95% CI: 0.21 to 0.86, P = 0.0174) Conclusions The ideal pregnancy outcome can be achieved within 19mm from uterus fundus after single blastocyst transfer, The clinical pregnancy and live birth at a distance of more 19mm from the uterus fundus have a cliff-like downward trend.

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