Live birth is not the only relevant outcome in research assessing assisted reproductive technology

The presence, clarity, and consistency of definitions in pregnancy outcomes in infertility trials: a systematic review

STUDY QUESTION

How frequently do infertility trials report live birth and pregnancy, and how consistently were their definitions reported?

SUMMARY ANSWER

One-third of 1425 infertility trials published in the last decade reported live birth, with one in eight reporting clinical pregnancy, ongoing pregnancy, and live birth concurrently; absent, ambiguous, or heterogeneous definitions were common.

WHAT IS KNOWN ALREADY

Absent or inconsistent outcome definitions in randomized controlled trials (RCTs) limit their interpretation and complicate subsequent evidence synthesis. While reporting live birth in infertility trials has been a long-running recommendation, the extent to which this is adhered to, and the temporal trend of adherence, is unclear. Furthermore, it is unknown if outcome reporting in infertility trials is clear and consistent.

STUDY DESIGN, SIZE, DURATION

We studied all RCTs in infertility published between 2012 and 2023. We aimed to assess (i) whether biochemical pregnancy, clinical pregnancy, ongoing pregnancy, and live birth were reported; the temporal trends in reporting these pregnancy outcomes, and compare the characteristics of trials reporting each type of outcome; (ii) whether and how these pregnancy outcomes were defined.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We systematically searched Embase, Medline, and CENTRAL for RCTs in infertility from January 2012 to August 2023. RCTs involving infertile women that reported either biochemical pregnancy, clinical pregnancy, ongoing pregnancy, or live birth were eligible. Secondary analyses, interim analyses, or conference abstracts were not eligible. Two authors independently screened articles. We extracted pregnancy definitions and trial characteristics primarily using text mining in R, a programming environment for data analysis, and supplemented by manual checking. The accuracy of extracted data was validated in a random sample of 50 articles, with sensitivity and specificity all at or above 90%.

MAIN RESULTS AND THE ROLE OF CHANCE

We included 1425 infertility RCTs. Among these, 419 (29.4%) reported biochemical pregnancy. While 1359 (95.4%) RCTs reported clinical pregnancy, 404 (28.4%) reported ongoing pregnancy, and 484 (34.0%) reported live birth, only 174 (12.2%) reported all three outcomes. The proportion of trials reporting live birth increased from 23.1% in 2012 to 33.7% in 2023. Trials reporting up to biochemical pregnancy or clinical pregnancy were more likely to be unregistered, smaller, single-centered, and published in non-first quarter journals. Definitions for biochemical, clinical, ongoing pregnancy, and live birth were provided in 68.5% (287/419), 64.5% (876/1359), 70.5% (285/404), and 41.1% (199/484) of articles reporting on these outcomes. Among 876 clinical pregnancy definitions, 63.4% (n = 555) specified the pregnancy confirmation timing. Of the 220 definitions that reported gestational weeks (ranging from 4 to 16 weeks), the most common cut-off was 6 weeks, used in 48.2% (n = 106) of cases. For ongoing pregnancy definitions, 96.1% (n = 274) of the 285 definitions included gestational age in weeks (ranging from 6 to 32 weeks), with 12 weeks being the most common cut-off used in 49.1% (n = 140) of definitions. Among 199 live birth definitions, 62.3% (n = 124) used a gestational age threshold (ranging from 20 to 37 weeks), with 24 weeks being the most common cut-off, used in 28.6% (n = 57) of trials.

LIMITATIONS, REASONS FOR CAUTION

Due to the vast data we needed to extract, we used text-mining supplemented by manual data extraction. While we optimized the text-mining algorithm attempting to identify all types of outcome definitions and manually curated all extracted definitions, definitions were missed in less than 10% of randomly checked studies, which is a limitation of this study. We only described definition patterns in published RCTs, and our results cannot be extrapolated to unpublished RCTs.

WIDER IMPLICATIONS OF THE FINDINGS

Despite long-standing recommendations to report live birth in infertility trials, in the last decade only a third of RCTs did so. This highlights a disconnection between the advocated outcome and what researchers are reporting. We observed an encouraging trend that there has been a consistent rise in the proportion of trials reporting live birth. Furthermore, the significant lack and variability of pregnancy definitions underscore the imperative to increase the dissemination and uptake of standardized pregnancy outcomes.

STUDY FUNDING/COMPETING INTEREST(S)

No funding was received for the study. Q.F. reports receiving a PhD scholarship from Merck. B.W.M. is supported by an NHMRC Investigator grant (GNT1176437). B.W.M. reports consultancy, travel support, and research funding from Merck and consultancy for Organon and Norgine. B.W.M. holds stock from ObsEva. W.T.L. is supported by an NHMRC Investigator grant (GTN2016729). W.L.L. reports receiving a PhD scholarship from the China Scholarship Council. T.D.H and S.L. are employees of Merck Healthcare KGaA, Darmstadt, Germany. R.W. is supported by an NHMRC Investigator grant (GTN2009767). The other author has no conflict of interest to declare.

REGISTRATION NUMBER

CRD42024498624.

One fresh cleavage-stage single embryo transfer (SET) plus one frozen-thawed blastocyst-stage SET or one fresh cleavage-stage double embryo transfer? A retrospective matched cohort study

STUDY QUESTION

Are there significant differences in fertility outcomes between transferring two cleavage-stage embryos in a single fresh cycle and transferring one cleavage-stage embryo in a fresh cycle and one blastocyst-stage embryo in the subsequent frozen-thawed cycle?

SUMMARY ANSWER

In women aged <38 years with two embryos available, transferring one cleavage-stage embryo in a fresh cycle and one blastocyst-stage embryo in the subsequent frozen-thawed cycle increased live birth rates and decreased multiple live birth rates compared to transferring two cleavage-stage embryos in a single fresh cycle.

WHAT IS KNOWN ALREADY

The strategy of repeated single embryo transfer (SET) has emerged as a solution to address the reduced live birth rates associated with SET per cycle. There is substantial evidence indicating that the cumulative live birth rate after repeated SET is comparable to that of double embryo transfer (DET), while significantly reducing the incidence of multiple pregnancies. Evidence regarding the outcomes of transferring two cleavage-stage embryos in a single fresh cycle versus transferring one cleavage-stage embryo in one fresh cycle and one blastocyst-stage embryo in the subsequent frozen-thawed cycle is scarce.

STUDY DESIGN, SIZE, DURATION

This study is a retrospective matched cohort study, where data were gathered from the clinical database of women who underwent IVF treatment at the Reproductive Center of Peking University Third Hospital between January 2011 and December 2019, with follow-up extending until December 2021.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The study group included cycles with a fresh cleavage-stage SET and a subsequent frozen-thawed blastocyst-stage SET (2xSET, N = 976). Fresh cleavage-stage DET was the control group (DET, N = 976). Included cycles were divided into subgroups based on age (≥38 years vs <38 years) and total number of utilizable (transferred or cryopreserved) embryos (=2 vs >2).

MAIN RESULTS AND THE ROLE OF CHANCE

The duration of infertility, prevalence of unexplained infertility, and controlled ovarian stimulation regimes differed significantly between the two groups and were adjusted for in the further analysis. We observed a significant increase in clinical pregnancies (55.5% vs 42%, adjusted odds ratio (OR) 1.87 [1.55-2.26]) and live births (44.8% vs 34.5%, adjusted OR 1.63 [1.35-1.97]) in favor of the 2xSET group. The preterm birth rate was lower in the study group (adjusted OR 0.64 [0.42-0.96]). Neonatal birth weight of singletons was similar between the two groups (adjusted B 4.94 g [-84.5 to 94.4]). The beneficial effect on the live birth rate disappeared in cases where aged 38 years and older or when only two embryos were utilizable.

LIMITATIONS, REASONS FOR CAUTION

This study is limited by differences in baseline characteristics of the two groups. Analyzing two consecutive SETs at the cleavage stage was not feasible. Additionally, the homogeneous population limits generalizability to other ethnic groups, which should be considered when interpreting the results broadly.

WIDER IMPLICATIONS OF THE FINDINGS

We recommend a combination strategy for women under 38 years old and with more than two embryos available: transfer one cleavage-stage embryo in the fresh cycle, followed by one blastocyst-stage embryo in the subsequent frozen-thawed cycle. This strategy reduces the risk of blastocyst culture failure while maintaining a high success rate. It offers hope to families seeking additional children and avoids unnecessary embryo disposal.

STUDY FUNDING/COMPETING INTEREST(S)

B.W.M. had received grants from NHMRC, Ferring, Merck, and Guerbet, consulting fees and stock options from ObsEva, is on the advisory board of ObsEva, and reports consultancy for Guerbet, none of which are in relation to the present manuscript. All other authors have no conflict of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Follitropin delta combined with menotropin in patients at risk for poor ovarian response during in vitro fertilization cycles: a prospective controlled clinical study

BACKGROUND

The maximum daily dose of follitropin delta for ovarian stimulation in the first in vitro fertilization cycle is 12 μg (180 IU), according to the algorithm developed by the manufacturer, and based on patient's ovarian reserve and weight. This study aimed to assess whether 150 IU of menotropin combined with follitropin delta improves the response to stimulation in women with serum antimullerian hormone levels less than 2.1 ng/mL.

METHODS

This study involved a prospective intervention group of 44 women who received 12 μg of follitropin delta combined with 150 IU of menotropin from the beginning of stimulation and a retrospective control group of 297 women who received 12 μg of follitropin delta alone during the phase 3 study of this drug. The inclusion and exclusion criteria and other treatment and follow-up protocols in the two groups were similar. The pituitary suppression was achieved by administering a gonadotropin-releasing hormone (GnRH) antagonist. Ovulation triggering with human chorionic gonadotropin or GnRH agonist and the option of transferring fresh embryos or using freeze-all strategy were made according to the risk of developing ovarian hyperstimulation syndrome.

RESULTS

Women who received follitropin delta combined with menotropin had higher estradiol levels on trigger day (2150 pg/mL vs. 1373 pg/mL, p < 0.001), more blastocysts (3.1 vs. 2.4, p = 0.003) and more top-quality blastocysts (1.8 vs. 1.3, p = 0.017). No difference was observed in pregnancy, implantation, miscarriage, and live birth rates after the first embryo transfer. The incidence of ovarian hyperstimulation syndrome did not differ between the groups. However, preventive measures for the syndrome were more frequent in the group using both drugs than in the control group (13.6% vs. 0.6%, p < 0.001).

CONCLUSIONS

In women with serum antimullerian hormone levels less than 2.1 ng/mL, the administration of 150 IU of menotropin combined with 12 μg of follitropin delta improved the ovarian response, making it a valid therapeutic option in situations where ovulation triggering with a GnRH agonist and freeze-all embryos strategy can be used routinely.

TRIAL REGISTRATION

U1111-1247-3260 (Brazilian Register of Clinical Trials, available at https://ensaiosclinicos.gov.br/rg/RBR-2kmyfm ).