Search

STUDY QUESTION What are the pregnancy and live birth rates for ovarian tissue transplantation and which factors are associated with the success rate? SUMMARY ANSWER Pregnancy and live birth rates per transplanted woman are 32.7% and 26.5% and success rate is associated with female age and first versus repeated transplantation. WHAT IS KNOWN ALREADY Live birth rates after ovarian tissue transplantations have been reported to be between around 24% and 41% per patient. Success rates seem to be negatively associated with increasing female age at the time of tissue cryopreservation and with pelvic radiation. Success rates are apparently not reduced after overnight transportation of ovarian tissue before freezing. STUDY DESIGN, SIZE, DURATION Registry analysis of 244 transplantations in 196 women, performed by 26 FertiPROTEKT network centres from 2007 to 2019 with follow-up till December 2020. PARTICIPANTS/MATERIALS, SETTING, METHODS Orthotopic ovarian tissue transplantations were performed in 196 women, 191 with previous malignant and 5 with previous non-malignant diseases. Size of transplanting centres varied between 1 and 100 transplantations per centre (median: 2). Factors possibly associated with success rate such as female age, first and repeated transplantation, experience of the transplanting centre and overnight transportation of the ovarian tissue before freezing were analysed. MAIN RESULTS AND THE ROLE OF CHANCE Average age of all 196 transplanted women was 31.3 years (SD 5.2; range 17–44) at the time of cryopreservation of tissue and 35.9 years (SD 4.8; range 23–47) at the time of transplantation. Pregnancy rate was 30.6% (95% CI, 24.2–37.6%) per first transplantation and 32.7% (95% CI, 26.1–39.7%) per patient. Pregnancy rate was higher after first transplantation (30.6% (95% CI, 24.2–37.6%)) compared to second and subsequent transplantations (11.8% (95% CI, 3.3–27.5%)). Live birth rate per first transplantation was 25.0% (95% CI, 19.1–31.7%) and per patient 26.5% (95% CI, 20.5–33.3%). Success rate decreased with increasing age at the time of ovarian tissue freezing. Live birth rate was 28.2% (95% CI, 20.9–36.3%) in women 35 years. Pregnancy rates after first transplantation were higher in centres who had performed ≥10 transplantations (35.1%) compared to centres with LIMITATIONS, REASONS FOR CAUTION The data were drawn from a registry analysis. Data such as ovarian reserve and premature ovarian insufficiency were not available for all women. Data might be influenced by different follow-up policies of the centres. WIDER IMPLICATIONS OF THE FINDINGS The study reveals the high potential of ovarian tissue freezing and transplantation, but only if freezing is performed in younger women. The study suggests focus should be placed on the first and not on repeated transplantations. It also opens the discussion of whether transplantation should rather be performed by experienced centres. STUDY FUNDING/COMPETING INTEREST(S) No funding. No competing interests. TRIAL REGISTRATION NUMBER N/A.

Obtaining a burning plasma is a critical step towards self-sustaining fusion energy1. A burning plasma is one in which the fusion reactions themselves are the primary source of heating in the plasma, which is necessary to sustain and propagate the burn, enabling high energy gain. After decades of fusion research, here we achieve a burning-plasma state in the laboratory. These experiments were conducted at the US National Ignition Facility, a laser facility delivering up to 1.9 megajoules of energy in pulses with peak powers up to 500 terawatts. We use the lasers to generate X-rays in a radiation cavity to indirectly drive a fuel-containing capsule via the X-ray ablation pressure, which results in the implosion process compressing and heating the fuel via mechanical work. The burning-plasma state was created using a strategy to increase the spatial scale of the capsule2,3 through two different implosion concepts4–7. These experiments show fusion self-heating in excess of the mechanical work injected into the implosions, satisfying several burning-plasma metrics3,8. Additionally, we describe a subset of experiments that appear to have crossed the static self-heating boundary, where fusion heating surpasses the energy losses from radiation and conduction. These results provide an opportunity to study α-particle-dominated plasmas and burning-plasma physics in the laboratory.

In a burning plasma state1–7, alpha particles from deuterium–tritium fusion reactions redeposit their energy and are the dominant source of heating. This state has recently been achieved at the US National Ignition Facility8 using indirect-drive inertial-confinement fusion. Our experiments use a laser-generated radiation-filled cavity (a hohlraum) to spherically implode capsules containing deuterium and tritium fuel in a central hot spot where the fusion reactions occur. We have developed more efficient hohlraums to implode larger fusion targets compared with previous experiments9,10. This delivered more energy to the hot spot, whereas other parameters were optimized to maintain the high pressures required for inertial-confinement fusion. We also report improvements in implosion symmetry control by moving energy between the laser beams11–16 and designing advanced hohlraum geometry17 that allows for these larger implosions to be driven at the present laser energy and power capability of the National Ignition Facility. These design changes resulted in fusion powers of 1.5 petawatts, greater than the input power of the laser, and 170 kJ of fusion energy18,19. Radiation hydrodynamics simulations20,21 show energy deposition by alpha particles as the dominant term in the hot-spot energy balance, indicative of a burning plasma state.

Study question What is the live birth rate of ovarian tissue transplantation and which factors are associated with the success rate? Summary answer Live birth rate per transplanted woman is 26.5% and the success rate is associated with female age and first versus repeated transplantation. What is known already Live birth rates after tissue transplantations have been reported to be between around 24% and 41% per patient. Success rates seem to be negatively associated with increasing female age at the time of tissue cryopreservation and with pelvic radiation. Success rates are apparently not reduced after overnight transportation of tissue before freezing. Study design, size, duration Registry analysis of 244 transplantations in 196 women, performed by 26 centers of the FertiPROTEKT network from 2007 to 2019 with a follow up till 12/2020. Participants/materials, setting, methods Orthotopic transplantation was performed in 196 women, 191 with previous malignant and 5 with previous non-malignant diseases. Size of transplanting centers varied between 1 and 100 transplantations per center (average: 9.5 ± 19.6 transplantations). Factors possibly associated with success rate such as female age, first and repeated transplantation, experience of the transplanting center and overnight transportation of the tissue before freezing were analysed. Main results and the role of chance Average age of all transplanted 196 women was 31.3 years (SD, standard deviation, 5.2) at the time of cryopreservation (range 17-44y) and 35.9 years (SD 4.8, range 23-47) at the time of first transplantation. Overall pregnancy rate was 30.6% (95% CI, 24.2-37.6%) per first transplantation and 32.7% (95% CI, 26.1-39.7) per patient. Overall live birth rate per first transplantation was 25.0% (95% CI, 19.1-31.7%) and per patient 26.5% (95% CI, 20.5-33.3%). Pregnancy and live birth rates were calculated and graphically expressed as a continuous function of age to allow estimation of success rates per age group. Success rate decreased with increasing age at the time of tissue freezing. Pregnancy rate after first transplantation was 34.5% (95% CI, 26.7-42.9%) in women Pregnancy rate was higher after 1st transplantation (30.6% (95% CI, 24.2-37.6%)) compared to 2nd and more transplantations (11.8% (95% CI, 3.3-27.5%)). Pregnancy rates after 1st transplantation was higher in centers with ≥10 transplantations (35.1%) compared to centers with Success rates was not different in women with and without overnight transportation of tissue before cryopreservation. Limitations, reasons for caution The data were drawn from a registry analysis. Data such as ovarian reserve and premature ovarian insufficiency were not available for all women. Data might be influenced by different follow up policies of the centers. Wider implications of the findings The study reveals the high potential of ovarian tissue freezing and transplantation but only if freezing is performed in younger women. The study suggests to better focus on the first and not on repeated transplantations. It also opens the discussion if transplantation should rather be performed by experienced centres. Trial registration number Non