No major differences in perinatal and maternal outcomes between uninterrupted embryo culture in time-lapse system and conventional embryo culture.

STUDY QUESTION: Is embryo culture in a closed time-lapse system associated with any differences in perinatal and maternal outcomes in comparison to conventional culture and spontaneous conception? SUMMARY ANSWER: There were no significant differences between time-lapse and conventional embryo culture in preterm birth (PTB, <37 weeks), low birth weight (LBW, >2500 g) and hypertensive disorders of pregnancy for singleton deliveries, the primary outcomes of this study. WHAT IS KNOWN ALREADY: Evidence from prospective trials evaluating the safety of time-lapse incubation for clinical use show similar embryo development rates, implantation rates, and ongoing pregnancy and live birth rates when compared to conventional incubation. Few studies have investigated if uninterrupted culture can alter risks of adverse perinatal outcomes presently associated with IVF when compared to conventional culture and spontaneous conceptions. STUDY DESIGN, SIZE, DURATION: This study is a Swedish population-based retrospective registry study, including 7379 singleton deliveries after fresh embryo transfer between 2013 and 2018 from selected IVF clinics. Perinatal outcomes of singletons born from time-lapse-cultured embryos were compared to singletons from embryos cultured in conventional incubators and 71 300 singletons from spontaneous conceptions. Main perinatal outcomes included PTB and LBW. Main maternal outcomes included hypertensive disorders of pregnancy (pregnancy hypertension and preeclampsia). PARTICIPANTS/MATERIALS, SETTING, METHODS: From nine IVF clinics, 2683 singletons born after fresh embryo transfer in a time-lapse system were compared to 4696 singletons born after culture in a conventional incubator and 71 300 singletons born after spontaneous conception matched for year of birth, parity, and maternal age. Patient and treatment characteristics from IVF deliveries were cross-linked with the Swedish Medical Birth Register, Register of Birth Defects, National Patient Register and Statistics Sweden. Children born after sperm and oocyte donation cycles and after Preimplantation Genetic testing cycles were excluded. Odds ratio (OR) and adjusted OR were calculated, adjusting for relevant confounders. MAIN RESULTS AND THE ROLE OF CHANCE: In the adjusted analyses, no significant differences were found for risk of PTB (adjusted OR 1.11, 95% CI 0.87-1.41) and LBW (adjusted OR 0.86, 95% CI 0.66-1.14) or hypertensive disorders of pregnancy; preeclampsia and hypertension (adjusted OR 0.99, 95% CI 0.67-1.45 and adjusted OR 0.98, 95% CI 0.62-1.53, respectively) between time-lapse and conventional incubation systems. A significantly increased risk of PTB (adjusted OR 1.31, 95% CI 1.08-1.60) and LBW (adjusted OR 1.36, 95% CI 1.08-1.72) was found for singletons born after time-lapse incubation compared to singletons born after spontaneous conceptions. In addition, a lower risk for pregnancy hypertension (adjusted OR 0.72 95% CI 0.53-0.99) but no significant difference for preeclampsia (adjusted OR 0.87, 95% CI 0.68-1.12) was found compared to spontaneous conceptions. Subgroup analyses showed that some risks were related to the day of embryo transfer, with more adverse outcomes after blastocyst transfer in comparison to cleavage stage transfer. LIMITATIONS, REASONS FOR CAUTION: This study is retrospective in design and different clinical strategies may have been used to select specific patient groups for time-lapse versus conventional incubation. The number of patients is limited and larger datasets are required to obtain more precise estimates and adjust for possible effect of additional embryo culture variables. WIDER IMPLICATIONS OF THE FINDINGS: Embryo culture in time-lapse systems is not associated with major differences in perinatal and maternal outcomes, compared to conventional embryo culture, suggesting that this technology is an acceptable alternative for embryo incubation. STUDY FUNDING/COMPETING INTEREST(S): The study was financed by a research grant from Gedeon Richter. There are no conflicts of interest for all authors to declare. TRIAL REGISTRATION NUMBER: N/A.

Effects of sediment type and intra- and interspecific competition on growth rate of the marine snails Hydrobia ulvae and Hydrobia ventrosa.

The combined effects of sediment grain size and intra- and interspecific competition on growth rate of Hydrobia ulvae and H. ventrosa were investigated in a 2-month laboratory experiment. Individuals of H. ulvae grew faster than H. ventrosa at all competition intensities. Growth rate did not differ between fine- and coarse-grained sediments in any of the species. This suggests that other factors than the sediment quality cause the often observed size differences between Hydrobia snails from these sediment types in nature. Competition from 1.6 to 1.9 times larger competitors affected growth of the smaller target snails. Competition between the species was asymmetrical and, in both species, per capita effect of competition was stronger from H. ulvae than from H. ventrosa, regardless of sediment type. From growth, Lotka-Volterra competition coefficients were estimated to 0.2 from H. ventrosa on H. ulvae and 1.8 from H. ulvae on H. ventrosa. Since competition between the species seems to be independent of sediment grain size, the shift in numerical dominance in nature, from H. ulvae on coarse-grained sediment to H. ventrosa on fine-grained, could not be explained with different competitive ability in different environments.

Influence on motility of Escherichia coli and Salmonella typhimurium by a naturally occurring conjugative plasmid.

In a collection of 45 R-plasmids, one was found to be associated with loss of motility of its Escherichia coli K-12 and Salmonella typhimurium host bacteria when tested in conventional motility agar. Genetic experiments, as well as analyses of deoxyribonucleic acid, showed that inhibition of motility was caused by a conjugative plasmid that was separate from the R-plasmid. This second plasmid, named pUM5, was fi- and mediated the same type of sex pilus (F-like) as the accompanying R-plasmid but lacked resistance determinants. Preliminary studies indicated that bacterial cells carrying the motility inhibition plasmid pUM5 were still equipped with flagella. The mechanism by which flagellar action is disturbed by the plasmid is presently not known.