• A systematic literature search was performed using electronic databases Medline, Embase, Pubmed and Cochrane Library to identify original and review articles addressing incubation parameters and intrauterine parameters (O2, pH and temperature) in the female reproductive tract.

• Studies published from 1946 to December 2017 were included in the search.

• Main search terms included: embryo parameters, time lapse incubators, single step and sequential culture media, pH, O2, temperature and intrauterine environment.

• IVF laboratories strive to mimic the environment, however despite advances in IVF, implantation rates remain low and pregnancy rates have plateaued1.

• Current criteria and methods for optimising incubator settings in the IVF laboratory are largely based on research and/or animal studies.

• There remains a lack of detailed knowledge of real-time parameters specifically: oxygen (O2), temperature and pH, and how fluctuations may impact embryo development.

PLASTICWARE(materials used < toxicity)

CULTURE MEDIUM(composition, pH, brand)

LIGHT(intensity and wavelength)

AIR QUALITY(presence of VOCs)

pH(Culture media, CO

concentration, bicarbonate)

INCUBATOR(environmental conditions)2

TEMPERATURE(laboratory and incubator)

GAS PHASE(mix, purity)

Figure 1: determinants of embryo development2

Blastocyst image courtesy of Complete Fertility Ltd (Member of Virtus Health)

In-vitro

Current criteria for optimising incubator parameters

METHODS

References:1. Assisted reproductive technology in Europe, 2013: results generated from European registers by ESHRE. European IVF-monitoring Consortium (EIM); European Society of Human Reproduction and Embryology (ESHRE), Calhaz-Jorge C, De Geyter C, Kupka MS, de Mouzon J, Erb K, Mocanu E, Motrenko T, Scaravelli G, Wyns C, Goossens V.Hum Reprod. 2017. 2. Coward and Wells, 2013, Cambridge University Press. 3. Lane and Gardner, 2003, 69, 1109-1117. 4. Swain, HRU, 2013, 18:333-339. 5. Wang et al, HRU, 2001, 16:2374-2378. 6. Bavister, Reprod Biomed Online, 2004 ,9:484-486. 7. Wale and Gardner, HRU, 2016, 22, 2-22. 8. Ng et al, Human Reproduction Update, 2017, pp 1-20.

• 15,858 records were identified and screened. 38 studies were included in this systematic review (26 pH, 7 temperature, 5 O2). Search terms included: embryo parameters, time lapse incubators, single step and sequential culture media, pH, O2, temperature and intrauterine environment. Studies were excluded if they only assessed uterine blood vessels flow, oxidative stress only, placental function, basal body temperature, increased body temperature and stress during injury, non-reproductive organ temperature, effects of temperature on chromosomes, changes of temperature and thermo-regulation during exercise, cervicovaginal microbiome or/and microflora, long term conditions and pH changes, immunomodulatory effects of pH change and drug induced pH changes.

• Chemical and physical factors influence incubator parameters and therefore impact on gamete and embryo development in IVF (Fig 1)2.

• pH regulates a variety of cellular processes and it is evident that very slight deviations in pH can affect the embryo significantly and impact blastocyst hatching, as well as gene expression3.

• The ideal pH to optimise human preimplantation embryo is still unknown4.

• Most laboratories set incubator temperature at 37°C as it is assumed that this mimics the temperature, however there is a lack of evidence that employing a tighter range of temperature on the incubator settings could improve outcomes5.

• O2 concentrations varies with the type of culture and the composition of commercial culture media.

• Hypoxic conditions has been noted in the uterus and low O2 (5%-5.5%) has been associated with more favourable clinical outcomes compared to atmospheric concentration6.

• There are many factors and variables which influence and control culturing embryo culture. Sources of stress on the human gametes and embryos include factors such as fluctuating pH, temperature and O27.

• Very little progress has been made in matching incubator parameters to uterine parameters.

• Although much effort is expended on mimicking the environment to improve success rates in IVF, the actual intrauterine biophysical conditions on which these are based remains poorly understood.

• There is a need to identify solutions to bridge the gap between the physiology and incubator conditions used in the IVF laboratory8.

• Advances in optimising IVF incubator environments may be halted by the fact that we have not characterised the environment of the womb, the ‘natural incubator’.

Ortega-Llarena Monika1, Ka Ying Bonnie Ng2, Macklon Nick1,3, Cheong Ying1,2,41 VivoPlex Medical, 1 Venture Road, University of Southampton Science Park, Southampton, SO16 7NP, United Kingdom, 2 Department of Obstetrics and

Gynaecology, Princess Anne Hospital, Coxford Road, Southampton, SO16 5YA, United Kingdom, 3 London Women’s Clinic, 113-115 Harley Street, Marylebone, London, W1G 6AP, United Kingdom, 4 Complete Fertility Ltd (Member of Virtus Health) Level G, Coxford Road, Southampton, SO16 5YA, United Kingdom.

Email: M.Ortega@vivoplex.com

INTRODUCTION

RESULTS DISCUSSION

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