In March 2020, the World Health Organization declared the onset of a SARS-CoV-2 pandemic , an unprecedented disease that counts almost 8,000,000 confirmed cases and more than 430,000 deaths worldwide (latest WHO data. Source: Health Emergency Dashboard, 16 June, 1:57 pm CEST). In particular, Italy has reported more than 237,000 confirmed with more than 34,000 deaths since the beginning of the pandemic (latest WHO data. Source: Health Emergency Dashboard, 16 June, 1:57 pm CEST).
COVID-19 is an acute respiratory disease caused by a single-stranded RNA virus, named Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). The extreme contagiousness of the infection, the high risk of developing a life-threatening infectious disease and the constant increase in cases of SARS-CoV-2 infection led to the pressing need for a widespread implementation of specific risk-reduction strategies, including the deferment of all non-essential activities (Phase I of Emergency). National and International Societies for Reproductive Medicine, as well as the Italian Authority for Assisted Reproductive Medicine, suggested to suspend new IVF treatments, nonessential cryopreservation of gametes, and diagnostic procedures (https://www.asrm.org/news-andpublications/covid19/statements/patient-management-and-clinical-recommendations-during-thecoronavirus-covid19-pandemic; https://www.sierr.it/images/Documenti/Raccomandazioni_SIERR_per_COVID-19.pdf; http://www.trapianti.salute.gov.it/imgs/C_17_cntAvvisi_232_0_file.pdf; http://www.trapianti.salute.gov.it/imgs/C_17_cntAvvisi_233_0_file.pdf; https://www.eshre.eu/Press-Room/ESHRE-News). These measures have been recommended due to the imperative necessity to reduce the risk of infection for IVF patients and healthcare workers, and to avoid overloading an already overburdened system (Bedford et al., 2020) .
Recently, in view of the declining epidemiological spread of SARS-CoV-2 infection, in agreement with the recommendations provided by Scientific Societies (De Santis et al., 2020) (https://www.eshre.eu/Press-Room/ESHRE-News#COVID19P2), the Italian authorities have expressed the need to re-start the IVF clinical activity (Phase II of emergency), mainly for timesensitive patients requiring urgent treatments (low prognosis couples who might lose their chance to conceive) (Bosch et al., 2019 . However, cautionary measures should be taken to ensure safe clinical practice and to minimize the risks associated with COVID-19 disease during treatment. The choice to re-start IVF treatments led to a change in IVF laboratory management and a re-definition of protocols and procedures to ensure personnel safety and prevent cross-contamination, in compliance with an effective quality management system to ensure good IVF laboratory practice in this emergency circumstances (Hickman et al., 2020) .
Before re-starting, each laboratory must build its own risk-reduction strategies, as a result of specific risk assessment analyses.
Failure mode and effects analysis (FMEA) is a step-by-step approach that can be applied to identify real or potential failures in processes and to develop measures to minimize risks according to the Joint Commission International (Rienzi et al., 2017 , Cimadomo et al., 2016 , Rienzi et al., 2015 . All the potential process failures are ranked according the occurrence of the failure and the chance to detect it and according to the severity of the consequences. The purpose of this FMEA is to define measures to eliminate or reduce failures associated to the different phases of the IVF treatment, starting with the highest-priority ones.
At our centers, we performed a multidisciplinary FMEA aimed at identifying corrective measures to reduce the risk of infection within the IVF laboratory. All the meetings were conducted online with the use of a web platforms. This manuscript describes this FMEA, which might be applied during the SARS-CoV-2 pandemic, as well as to minimize the risk of any other aerosol-mediated infection.
This FMEA is addressed to laboratory managers, supervisors and clinical embryologists.
The FMEA was conducted by a multidisciplinary team involving different members of the IVF laboratory staff operating in four different GENERA centers (Rome, Marostica, Naples, Umbertide) and covering different responsibilities within the organization chart: IVF Clinical and Lab Directors, Embryology and Andrology Lab supervisors, Senior Clinical embryologists, Scientific Coordinator and Quality Management Manager, nurse and administrative. Three web meetings were necessary to conclude the evaluations. The FMEA was focused specifically on the management of the clinical activity of the IVF laboratory. In fact, the administrative and counseling activities were deemed to follow the general guidelines outlined for any other work environment.
Similarly, the definition of the first patients' populations to admit to the treatment was already described elsewhere along with the general rules to adopt for consultations, monitoring of ovarian stimulation and suggested clinical strategies ("A statement from ESHRE for phase 2 -ESHRE Guidance on recommencing ART treatments" on the web page https://www.eshre.eu/Press-Room/ESHRE-News#COVID19P2).
First, a schematic representation of new protocols and procedures adopted during COVID-19 emergency has been outlined, including directives to the staff of the behavior to adopt when entering the clinic and the embryology lab, in case of face-to-face contacts with patients (during patients identification, embryological consultation) and for any case of close contact between staff members (in the changing room, during the lab procedures, coffee and lunch break, meetings and journal clubs). The discussion was based on the recommendations and guidelines of both national and international scientific societies ("A statement from ESHRE for phase 2 -ESHRE Guidance on recommencing ART treatments" on the web page https://www.eshre.eu/Press-Room/ESHRE-News#COVID19P2; https://www.britishfertilitysociety.org.uk/wp-content/uploads/2020/05/ARCS-BFS-COVID-19-guideline-v1.1-1.pdf; https://www.asrm.org/globalassets/asrm/asrm-content/newsand-publications/covid-19/covidtaskforceupdate4.pdf)(De Santis et al., 2020) Secondly, the risk of cross-contamination between samples belonging to different patients during cell handling and manipulation has been also evaluated. Finally, potential failure modes for each phase have then been analyzed, focusing on possible sources of error, defined by three parameters: occurrence (O), severity (S) and detection (D). A risk priority number score (RPN) has been then calculated as a product of the three factors (RPN= O x S x D) according to the Joint Commission International. The scoring system was discussed by the team and is summarized in Table 1 . RPN values between 1 and 15 indicate a low risk of failure, between 15 and 50 a moderate risk and over 50 a high risk of failure.
Although during the early phase of COVID-19 emergency, preventive measures were urgently adopted to contrast/contain the transmission of the virus, during the laboratory shutdown we could perform a risk assessment analysis. This assessment considered the different nature of the viral transmission and aimed at identifying those laboratory procedures needing to be reviewed and adapted to safeguard patients, staff, gametes and embryos. We considered necessary then to perform a second analysis to re-assess the real effectiveness of the preventive measures adopted in the Phase II (re-starting phase). FMEA was considered the most effective approach to estimate how our new protocols could reduce the incidence of the risk of failure and increase chance to detect it. This FMEA has been focused on failure modes associated with different process phases of IVF laboratory practice. Considering the limited predictive value of available assessment methods for patients and health care staff COVID-19 infections (https://www.eshre.eu/Press-Room/ESHRE-News#COVID19P2) and given the high incidence of asymptomatic carriers, the whole population was considered as potentially infected. Although this may lead to an overestimation of the risks, any failure mode has been considered as a potential direct / indirect source of infection.
Four main areas at potential risk for bi-directional infection have been identified: Patient-Staff, Staff-Staff, Staff-Cell and Cell-Cell. All the risk modes, causes of infection, estimated O, S and D for each phase before and after the implementation of the corrective measures are described in Tables 2-5. The estimated S of these failures has been considered "high" when the person infected was the patient and/or the operator; instead "low", when the risk was of cell cross-contamination.
The O of these liable situations was variable between "low" and " high" and has been calculated according to the number of times each particular step is performed during the work activity. Before the COVID-19 pandemic was declared, the low probability to detect a failure and prevent the onset of risk was mainly due to the absence of triage procedures for both patients and operators and the related difficulty of performing a certain and definite diagnosis of COVID-19 infection. After the first risk assessment analysis, generic health precautions have been adopted as corrective measures.
The access to the clinic has been restricted to the patient performing the IVF treatment and to the IVF team on duty. Patients were screened by telephone pre-triage prior to attendance and instructed to postpone their treatment if they were suspected of having any possible COVID-19 symptomatology (fever, cough, dyspnea, etc.) or they have been in close contact with a confirmed or suspected case of COVID-19. When entering the clinic, both patients and staff underwent a triage and were interviewed on the presence of respiratory symptoms and screened by a thermo scanner. General personal protective equipment (PPE), such as and surgical facemasks, gloves and cover shoes were provided at the entrance to minimize the risk of transmission. Separate pathways have been defined for health care staff and patients respectively, and within the clinic the different pre-clinical and administrative areas have been organized to guarantee a safe interpersonal distance.
All non-essential visits by external providers and engineers have been postponed. For planned maintenance of critical instruments, detailed protocols and procedures have been developed together with a specific triage procedure that entails body temperature control and evaluation of technicians' symptoms before the intervention. All the supplies for the laboratory are delivered at specific entrances. All patients' embryological consultations are performed via telemedicine or phone call. Operating theatre daily scheduling has been revised to reduce the number of IVF operators on duty; two shift groups of operators have been defined in order to be able to continue guaranteeing laboratory activity even in the event of the onset of a positivity requiring the quarantine of the whole group. The time between procedures has been increased to allow for full air exchange in the operating theatre (calculated according to the air change rate of the room and its volume). The whole staff has been trained of the new procedures and the correct use of PPE and their compliance has been verified through audit systems. In the laboratory area, the frequency of ordinary and extraordinary surfaces and equipment disinfection has been revised and implemented and the planned maintenance of air filtration system has been anticipated. The efficacy of the implemented corrective measures in reducing potential risks of infection has been confirmed in the revised FMEA: all the procedures at higher risk of infection showed a significant reduction in RPN value (Tables 2-5 ).
The resumption of post-emergency COVID-19 clinical activity (Phase II of emergency) has involved a substantial re-organization of work in the IVF laboratories, a revision of the existing protocols and the implementation of new operative procedures. All the basic precautions usually adopted during the IVF practice have been focused on the prevention of the risk of crosscontamination by blood-borne viral infections such as Human Immunodeficiency Virus, Hepatitis B virus and Hepatitis C virus. Now, we had to face and manage an unprecedented emergency, not only because of the extreme contagiousness of the virus, but also because of its different intrinsic nature. The risk of transmission of other infectious respiratory viruses, such as Influenza viruses, and the impact of their spreading on the IVF clinical activity had never been considered before.
In the field of occupational health, the risk of infection for healthcare operators can be reduced by logistic measures to lower the exposure (Verbeek et al., 2020) . Therefore, the first important precautionary measure was a proper organization of the operational unit to avoid unnecessary strict contacts. In the presence of highly contagious viruses, such as SARS-CoV2, healthcare workers represent a category with a higher risk of infection with respect to the general population, due to the frequent exposure of mucous membranes of the eyes, mouth or nose to biological fluids (follicular and seminal fluids) or to exhaled droplets released by potentially contaminated patients. , Li et al., 2020b , Burke et al., 2020 All medical appointments and procedures have been scheduled at a time distance of at least 1.5 hours in order to reduce the number of people present at the same time within the clinic and to allow appropriate and complete air exchange within the various rooms. All procedures have been therefore revised to allow an interpersonal spacing of more than one meter, except for witnessing and embryo transfer procedures that have a shorter time duration (less than 15 minutes). All embryological consultations with patients, as well as team meetings, journal clubs, the discussion of clinical cases were carried out through web communication.
Still, there is the risk that an infected operator might spread the infection to healthy patients or act as a vector of transmission of the infection between patients. Therefore, as for patients, all
embryologists have been considered potentially-infectious and continuous monitoring of IVF staff by daily triage has been implemented.
After the implementation of logistic measures, the correct use of appropriate PPE to prevent contamination of skin and mucous membranes is the second most important strategy that can be easily implemented for both patients' and embryologists' safety (Adams and Walls, 2020, Chang et al., 2020) . The additional PPEs adopted in the IVF laboratory during this pandemic have been (Hickman et al., 2020) . When conducting procedures at higher risk of infection due to presumptive higher viral load (e.g. while handling biological fluids during oocyte retrieval and sperm processing), double gloves are used, since, in case of improper sample preparation or accidental breakage of the container, the operator and the cells could be exposed to a higher risk of infection. An additional pair of gloves decreases also the risk of contamination when doffing PPEs (Casanova et al., 2012) . Clearly, beyond the use of PPEs, the frequency of hand washing and sanitation (for at least 20 seconds) has been also increased, standing its crucial role in preventing skin contamination (Gould et al., 2010 , Hickman et al., 2020 .
In closed-controlled air systems, the airflow may increase the virus spreading even from asymptomatic patients and/or from healthcare operators (Zimmermann and Nkenke, 2020) . Thus, the efficiency of our air filtration systems in the operating theatre and laboratory areas and air pressurization has been checked before re-starting (Mortimer et al., 2018) . Scheduled interventions every 1.5 hours guarantee sufficient air renewal between one procedure and another, which, together with the implementation of validated disinfection procedures between interventions, allows minimizing the risk of spreading a putative infection. In addition, an increased temporal interval between oocyte retrievals allows us to operate safely and efficiently, even in presence of reduced number of operators on duty, always respecting the correct timings for the execution of the procedures, a key process indicator for IVF laboratories , Maggiulli et al., 2019 . The laboratory working areas have been defined so that at least a 1 meter safety distance can be guaranteed between the operators. This, in turn, allowed to reduce the number of operators on duty without compromising the efficiency of the laboratory, mainly thanks to the automated technologies that had been previously implemented in our clinics (Electronic Witnessing System, time-lapse incubation, automated equipment monitoring and alarm systems).
Two shift working groups have been organized to limit the spread of the virus in case of infection and to continue guaranteeing laboratory activities even in the event of a positivity requiring the quarantine of a whole group.
Before re-considering laboratory procedures, the risk of transmission of viral contamination to embryos or gametes, either from contaminated cells or infected operators, has been evaluated. The former possibility was assumed unlikely since recent peer-reviewed publications suggested no presence of SARS-CoV2 in several biological fluids (vaginal secretions, semen or testicular tissue)
in patients diagnosed with COVID-19 , Qiu et al., 2020 , Song et al., 2020 , Paoli et al., 2020 , and even when a the presence of the SARS-CoV-2 virus was reported, potential infectivity was not proven (Li et al., 2020a) .
Although limited data are available, it was assumed unlikely that sperm, oocytes and embryos might be infected, since all IVF procedures require systematic washing and processing of the Nevertheless, we considered that an infected operator may spread Sars-Cov2 during the various laboratory manipulations, as well as during all the preliminary phases to the effective handling and micromanipulation procedures, which previously did not require the mandatory use of PPE (e.g.
cryo-device labeling before cryopreservation). In particular, the risk assessment analysis reported a higher possibility of failure associated with the management of biological material in the cryo-storage room, which can be considered as a high-risk area. The classification of this environment did not involve the specific PPEs (except for the cryogenic ones) to reduce the risk of viral infection per se, but all cryo-devices storage procedures require a second witness, who could equally be a source of contamination. Therefore, the cryo-storage was ranked as the most sensitive step of the whole IVF procedure. Being SARS-CoV-2 an enveloped RNA virus, it may maintain its viability even at the low temperatures of liquid nitrogen, thus leading to possible contamination and/or crosscontamination between samples (Bielanski, 2012) . However, as mentioned before, the multiple washings to which gametes and embryos are subject before being cryopreserved, associated with the small volumes involved in the vitrification procedure (about 0.l μl), suggest that if a minimal viral load is present, it will not be sufficiently titrated to represent a source of infection. Therefore, in order not to affect the effectiveness of the procedure, the protocols for cryopreservation of implemented for the washing of cryodevices at thawing time (Parmegiani et al., 2012) , or when importing gametes from other laboratories after the pandemic will be over (Yakass and Woodward, 2020) . As a matter of fact, due to patients' impossibility to travel around Italy or abroad, the demand of samples importation has increased and must be carefully managed from now on.
In all other lab procedures, the risk of contamination has been reduced by simply suggesting the use of PPEs at all steps and increasing the frequency of equipment and surface disinfections (with quaternary ammonium salts) carried out not only between different patients, but also between operators. During culture, in order to reduce the number of handlings of embryos, single-step culture has been adopted as preferential culture system.
This is the perspective of a group of four Italian IVF laboratories and represents an example that might be adopted with all due adjustments by other IVF laboratories worldwide. Every IVF laboratory is in fact invited to perform its own risk assessment analyses.
This FMEA is addressed to the clinical embryologists who manage and/or work in an IVF laboratory, since we considered it a peculiar work environment requiring specific procedures and corrective measures to prevent/minimize the risks of infection.
The efficacy of these corrective measures cannot be supported by specific data regarding actual infections. Nevertheless, according to a survey of the Italian Society of Embryology, Reproduction and Research (SIERR), updated at the 15 th of May 2020, 11% of the responding Italian IVF laboratories (n=5/46) reported at least one infected operator ("COVID-19 does not stop fertility preservation: The Italian situation during the pandemic emergency"; oral presentation ESHRE 2020). Luckily up to date, possibly also due to the corrective measures implemented and described here, we have not reported any case of COVID-19 among treated patients and operators working at our IVF centers in four Italian regions, one of which is located in Veneto (i.e. one of the mostlyaffected areas).
This FMEA is based on the current knowledge on SARS-CoV-2 infectivity and its effect on human reproduction, and a clinical situation which is still fluid at present. Thus it is subject to possible future modifications. Yet, as stated previously, we preferred to over-estimate the risks and adopt a conservative approach with the aim of preventing any infection among patients, personnel and gametes.
During the COVID-19 pandemic, the risk of infections of IVF laboratory workers and patients as a result of accidental exposure to biological fluids or contaminated material became more concerning.
We considered our standard laboratory protocols insufficient to face a virus whose transmission is aerosol-mediated. The revision of all procedures and the implementation of further preventive measures has instructed us about the precautionary approach required now, as well as in the future, aimed at reducing the consequences of any aerosol-mediated infection. In fact, these measures might be adopted to face even less severe viruses such as influenza, whose impact on the management of an IVF laboratory is less severe than SARS-CoV-2, but not completely negligible (i.e. staff reduction and patients' health).