A recurrent nova super-remnant in the Andromeda galaxy

The accretion of hydrogen onto a white dwarf star ignites a classical nova eruption^1,2-a thermonuclear runaway in the accumulated envelope of gas, leading to luminosities up to a million times that of the Sun and a high-velocity mass ejection that produces a remnant shell (mainly consisting of insterstellar medium). Close to the upper mass limit of a white dwarf³ (1.4 solar masses), rapid accretion of hydrogen (about 10^-7 solar masses per year) from a stellar companion leads to frequent eruptions on timescales of years^4,5 to decades⁶. Such binary systems are known as recurrent novae. The ejecta of recurrent novae, initially moving at velocities of up to 10,000 kilometres per second⁷, must 'sweep up' the surrounding interstellar medium, creating cavities in space around the nova binary. No remnant larger than one parsec across from any single classical or recurrent nova eruption is known^8-10, but thousands of successive recurrent nova eruptions should be capable of generating shells hundreds of parsecs across. Here we report that the most frequently recurring nova, M31N 2008-12a in the Andromeda galaxy (Messier 31 or NGC 224), which erupts annually¹¹, is indeed surrounded by such a super-remnant with a projected size of at least 134 by 90 parsecs. Larger than almost all known remnants of even supernova explosions¹², the existence of this shell demonstrates that the nova M31N 2008-12a has erupted with high frequency for millions of years.

The slow growing embryo and premature progesterone elevation: compounding factors for embryo-endometrial asynchrony

STUDY QUESTION

Is there an association of progesterone (P₄) on the day of trigger with live birth in autologous ART transfer cycles on day 5 versus day 6?

SUMMARY ANSWER

P₄ had a greater negative effect on live birth in day 6 fresh transfers compared to day 5 fresh transfers.

WHAT IS KNOWN ALREADY

Premature P₄ elevation is associated with lower live birth rates in fresh autologous ART cycles, likely due to worsened endometrial-embryo asynchrony. Few studies have evaluated whether the effect of an elevated P₄ on the day of trigger is different on live birth rates with a day 5 compared to a day 6 embryo transfer.

STUDY DESIGN SIZE, DURATION

This was a retrospective cohort study with autologous IVF cycles with fresh embryo transfers on day 5 and day 6 from 2011 to 2014. A total of 4120 day 5 and 230 day 6 fresh autologous embryo transfers were included. The primary outcome was live birth, defined as a live born baby at 24 weeks gestation or later.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Patients from a large private ART practice were included. Analysis was performed with generalized estimating equations (GEE) modeling and receiver operating characteristic (ROC) curves.

MAIN RESULTS AND THE ROLE OF CHANCE

Day 6 transfers were less likely to have good quality embryos (73% versus 83%, P < 0.001) but the cohorts had similar rates of blastocyst stage transfer (92% versus 91%, P = 0.92). Live birth was less likely in fresh day 6 versus day 5 embryo transfers (34% versus 46%, P = 0.01) even when controlling for embryo confounders. In adjusted GEE models, the effect of P₄ as a continuous variable on live birth was more pronounced on day 6 (P < 0.001). Similarly, the effect of P₄ > 1.5 ng/ml on day of trigger was more pronounced on day 6 than day 5 (P < 0.001). Day 6 live birth rates were 8% lower than day 5 when P₄ was in the normal range (P = 0.04), but became 17% lower when P₄ was > 1.5 ng/ml (P < 0.01). ROC curves for P₄ predicting live birth demonstrated a greater AUC in day 6 transfers (AUC 0.59, 95% CI 0.51-0.66) than day 5 (AUC 0.54, 95% CI 0.52-0.55). Interaction testing of P₄ × day of embryo transfer was highly significant (P < 0.001), further suggesting that the effect of P₄ was more pronounced on day 6 embryo transfer. In fresh oocyte retrieval cycles with elevated P₄, a subsequent 760 frozen-thaw transfers did not demonstrate a difference between embryos that were frozen after blastulation on day 5 versus 6.

LIMITATIONS REASONS FOR CAUTION

Limitations include the retrospective design and the inability to control for certain confounding variables, such as thaw survival rates between day 5 and day 6 blastocysts. Also, the data set lacks the known ploidy status of the embryos and the progesterone assay is not currently optimized to discriminate between patients with a P₄ of 1.5 versus 1.8 ng/ml.

WIDER IMPLICATIONS OF THE FINDINGS

This study suggests further endometrial-embryo asynchrony when a slow growing embryo is combined with an advanced endometrium, ultimately leading to decreased live births. This suggests that premature elevated P₄ may be a factor in the lower live birth rates in day 6 fresh embryo transfers. Further studies are needed to evaluate if a frozen embryo transfer cycle can ameliorate the effect of elevated P₄ on the day of trigger among these slower growing embryos that reach blastocyst staging on day 6.

STUDY FUNDING/COMPETING INTERESTS

No external funding was received for this study. There are no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

Not applicable.

Does elevated progesterone on day of oocyte maturation play a role in the racial disparities in IVF outcomes?

The aim of this study was to evaluate if premature progesterone elevation on the last day of assisted reproduction technique stimulation contributes to racial disparities in IVF outcome. A total of 3289 assisted reproduction technique cycles were evaluated in Latino, Asian, African American, and white women. Live birth was more likely in white women (42.6%) compared with Asian (34.8%) and African American women (36.3%), but was similar to Latino women (40.7%). In all racial groups, progesterone was negatively associated with live birth and the negative effect of progesterone persisted when adjusting for confounders. Although the effect of elevated progesterone was similar in all racial groups, the prevalence of elevated progesterone differed. Progesterone > 1.5 ng/ml occurred in only 10.6% of cycles in white women compared with 18.0% in Latino and 20.2% in Asian women. Progesterone > 2 ng/ml occurred in only 2.3% of cycles in white women compared with 6.3% in Latino, 5.9% in Asian and 4.4% in African American women. The increased prevalence of premature elevated progesterone persisted when controlling for IVF stimulation parameters. In conclusion, premature progesterone elevation had a negative effect on live birth in all racial groups studied. The prevalence of elevated progesterone was higher in racial minorities.

Seminal vesicle sperm aspiration from wounded warriors

OBJECTIVE

To assess whether seminal vesicle sperm aspiration (SVSA) is an option for wounded warriors with severe genital and testicular injuries, with the goal of cryopreservation to use in future assisted reproductive technology (ART) cycles.

DESIGN

Retrospective case series.

SETTING

Tertiary care military hospital.

PATIENT(S)

Six wounded warriors.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Seminal vesicle fluid analysis after harvest, after thaw analysis, fertilization rates, pregnancy rates (PRs), live birth.

RESULT(S)

Six patients with lower extremity, pelvic, and genital injuries from dismounted improvised explosive devices underwent SVSA within 5-12 days of the initial injury. Sperm retrieved were analyzed (volume, 0.4-1.8 mL; concentration, 40-2,200 K; motility, 0-5%), washed, and cryopreserved. Two patients underwent IVF/intracytoplasmic sperm injection (ICSI) cycles using their samples. In one couple, fertilization rate was 38%. One grade V embryo was transferred with a negative pregnancy test. The second couple underwent two cycles. In their first cycle, fertilization rate was 44%, with one blastocyst transferred and a negative pregnancy test. In the second cycle, fertilization rate was 47%. Two blastocysts were cryopreserved due to ovarian hyperstimulation syndrome (OHSS) concerns. One blastocyst was later transferred in a frozen cycle resulting in a live birth.

CONCLUSION(S)

The SVSA is a reasonable option to retrieve sperm in wounded warriors or trauma patients with extensive genital injuries.

Is the effect of premature elevated progesterone augmented by human chorionic gonadotropin versus gonadotropin-releasing hormone agonist trigger?

OBJECTIVE

To compare the effect of P on live birth rate between hCG and GnRH agonist (GnRH-a) trigger cycles.

DESIGN

Retrospective cohort study.

SETTING

Large private assisted reproductive technology (ART) practice.

PATIENT(S)

A total of 3,326 fresh autologous ART cycles.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Live birth.

RESULT(S)

A total of 647 GnRH-a trigger cycles were compared with 2,679 hCG trigger cycles. Live birth was negatively associated with P in both the hCG trigger (odds ratio [OR] 0.62, 95% confidence interval [CI] 0.52-0.76) and the agonist trigger cohorts (OR 0.56, 95% CI 0.45-0.69). Interaction testing evaluating P and trigger medication was not significant, indicating that P had a similar negative effect on live birth rates in both cohorts. Progesterone ≥2 ng/mL occurred more commonly in GnRH-a trigger cycles compared with hCG trigger cycles (5.5% vs. 3.1%) and was negatively associated with live birth in both the hCG trigger (OR 0.28, 95% CI 0.11-0.73) and agonist trigger cohorts (OR 0.35, 95% CI 0.14-0.90). When P ≥2 ng/mL, the live birth rates were poor and similar in the hCG and GnRH-a cohorts (5.9% vs. 14.2%), indicating that P ≥2 ng/mL had a similar negative effect on live birth in both cohorts.

CONCLUSION(S)

Elevated serum P on the day of hCG was negatively associated with live birth rates in both hCG and GnRH-a trigger cycles.

Are good patient and embryo characteristics protective against the negative effect of elevated progesterone level on the day of oocyte maturation?

OBJECTIVE

To evaluate if an elevated progesterone (P) level on the day of human chorionic gonadotropin (hCG) administration is associated with a decrease in live-birth rate in patients with a good prognosis.

DESIGN

Retrospective cohort study.

SETTING

Large, private, assisted reproductive technology (ART) practice.

PATIENT(S)

One thousand six hundred twenty fresh autologous ART cycles.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Live-birth rate.

RESULT(S)

A total of 934 blastocyst and 686 cleavage-stage embryo transfer (ET) cycles were evaluated. Serum P levels were not associated with markers of oocyte or embryo quality, including fertilization, embryo stage at transfer, and embryos available for cryopreservation. Patient age, stage of ET, embryo quality, the number of embryos transferred, and P level on the day of hCG administration were all significantly associated with live birth. Higher P levels were associated with decreased odds of live birth for cleavage- and blastocyst-stage embryos, poor-fair and good-quality embryos, and poor- and high-responder patients. The nonsignificance of interaction tests of P levels with embryo stage, embryo quality, patient age, and ovarian response indicated that the relationship between P level and live birth was similar regardless of these factors.

CONCLUSION(S)

An elevated serum P level on the day of hCG administration was negatively associated with live birth, even in ETs with a good prognosis.