https://orcid.org/0000-0002-2585-3769
Abstract
Vaginal lubricants are commonly used to aid sexual pleasure and/or to help combat vaginal dryness and dyspareunia. Several studies have reported their impact on sperm function, however there are no published guidelines to help healthcare professionals and couples select a vaginal lubricant that is ‘sperm-safe’. To address this, we conducted a literature search using both PubMed and Scopus to identify and appraise manuscripts that reported the impact of lubricants on sperm function. We did not restrict the literature search by year of publication, and we only included manuscripts that looked at the impact of vaginal lubricants on human sperm. The quality of the eligible studies was assessed using the Björndahl et al., (Citation2016) checklist for semen analysis, as most of the studies reported the findings of a basic semen analysis. A total of 24 articles were eligible for analysis with a total of 35 vaginal lubricants (that were available to buy over the counter) being included, 2 of which studied the effect of vaginal lubricants on sperm function in vivo, and 22 being conducted in vitro. KY Jelly, PreSeed and Astroglide were most studied, with most manuscripts focussing on their impact on sperm motility. A paucity of data on most lubricants combined with methodological variations between studies and limited/no reporting on pregnancy outcomes means greater efforts are required before an evidence-based guideline can be published.
Introduction
Problems with vaginal lubrication have been identified as a factor leading to dyspareunia, which has been shown to impact natural conception (Ellington et al., Citation2003). Vaginal lubricants (VLs) are commonly used to help mitigate against this, but may also be used by couples to enhance pleasure during intercourse, and in fertility clinics during semen collection. Steiner et al. (Citation2012) surveyed 296 women in the US who were actively trying to conceive (TTC) and found 25% had stated that they used a VL whilst trying to conceive. Whereas in the UK, a survey estimated ∼10% of the 1,549 women who participated in the survey reported that they used a VL when TTC, but only 3% of the women would use it explicitly when experiencing vaginal dryness (Johnson et al., Citation2016).
Whilst VLs are commonly used worldwide, are easily accessible for most couples, and are considered relatively safe to use, there is little to no official guidance or recommendations by healthcare professionals regarding the knowledge and understanding of VL use, as illustrated by in previous studies (Mackenzie & Gellatly, Citation2019). The authors surveyed UK-based healthcare professionals in fertility clinics and found the majority responded with ‘rarely or never have asked patients about lubricant use during a clinical history’. It was also identified that most of the respondents (>80%) would not recommend lubricant use for couples trying to conceive a pregnancy unless it is to help with vaginal dryness during intercourse. Whilst it was not highlighted by the participants of the survey why did they not recommend VL use for couples TTC, this can be attributed to two factors: (i) the general lack of knowledge or awareness surrounding common lubricant use and impact on fertility, specifically male fertility, or (ii) due to personal professional opinions the healthcare practitioners may have of lubricant use during intercourse. Wilhite (Citation2018) has reviewed and provided appropriate recommendations for clinicians when dealing with patients struggling with vaginal dryness and what kind of VL to choose or recommend, however there was no mention or consideration for the impact the VLs may have on sperm.
Although several studies have reported the impact of VL on sperm function, there has yet to be a robust synthesis of evidence from these studies. Given the prevalence of VL usage among couples and limited knowledge surrounding their impact on sperm function among healthcare professionals (HCPs), this review was urgently required to help the development of an evidence-based guidance to prevent trying-to-conceive couples and HCPs from choosing an inappropriate VL. Therefore, the aim of this study was to perform a systematic review of the available data on the effect of VL on sperm function to see whether there is sufficient evidence to formulate evidence-based guidelines for couples and HCPs.
Materials and methods
Literature review strategy
A systematic literature search was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (Moher et al., Citation2009). PubMed and Scopus databases were searched (start date of March 2022) to identify peer-reviewed, English language manuscripts reporting the impact of VLs on human sperm function. No restrictions on the year of publication were imposed at the time of data collection.
For PubMed, the keywords, and Boolean operators (AND/OR) used were (‘lubricants’[Title/Abstract] AND ‘sperm’[Title/Abstract]) AND (‘sperm motility’ OR ‘sperm function’ OR ‘DNA integrity’ OR ‘DNA fragmentation’ OR ‘glycerine’ OR ‘glycerol’). For Scopus, the keywords and Boolean operators used were (TITLE-ABS-KEY (‘lubricants’ AND ‘sperm’) AND KEY (‘sperm motility’ OR ‘sperm function’ OR ‘DNA integrity’ OR ‘DNA fragmentation’ OR ‘glycerine’ OR ‘glycerol’)).
All manuscripts identified in our search were subsequently downloaded using Endnote X9.3.3 (Clarivate, Philadelphia, PA) to pool the records together prior to manuscript screening. Following the removal of duplicates (n = 19), titles and abstracts were screened for their relevance to the present review’s aim: Vaginal lubricants’ impact on human sperm function, in vivo or in-vitro. After abstracts were screened, the remaining articles (n = 28) were eligible for full-text review to assess their suitability using our inclusion and exclusion criteria. Our inclusion criteria were as follows: the article had to primarily investigate the human spermatozoa; the article had included a vaginal lubricant(s) as part of the study's main treatment for analysis; the manuscript was a primary research manuscript or a short communication; the manuscript included testing against sperm functional parameters such as motility, DNA damage, vitality, sperm toxicity, or sperm quality; the manuscript was either an in-vivo or an in-vitro study; the manuscript was written in English as the main text; and the manuscript was published as either final print or ahead of print. We excluded manuscript based on the following: the manuscript primarily focused on animal spermatozoa or was an animal-based study; the manuscript did not discuss the resultant impact on sperm function(s) after VL treatment or use; the manuscript was exclusively investigating the effects and use of spermicidal or contraceptive lubricants against human spermatozoa; the manuscript was a review or a commentary; or the manuscript was not written in English as the main text. illustrates the flow chart of the PRISMA guidelines and reasons for exclusion of records for this review.
Figure 1. PRISMA flowchart for the identification and selection of studies investigating vaginal lubricants influence over sperm function in in vivo and in vitro settings.
Following identification of eligible manuscripts, compounds that were studied or tested as ‘vaginal lubricants’ were quantified and then sub-divided into three main categories: (i) Over the Counter (OTC) refers to products that would be easily accessible for an individual or couple to purchase and find them, (ii) non-OTC refers to products that are more likely to be used in clinical and healthcare settings, such as gynaecological examinations or in laboratories and are not usually purchased by the general public, and (iii) Discontinued refers to those products that are currently unavailable in the market, either OTC or Non-OTC, since their time of study. A review protocol was not previously prepared and is not registered.
Traffic light system
A Red, Amber or Green (RAG) traffic light system was used to rate the effect of VL on sperm function, based on a similar approached that was created by the Human Fertilization and Embryology Authority (HFEA) for add-ons. Briefly, a red, amber or green colour rating is assigned to each VL identified in this review based on whether the evidence from the studies suggests that it affects sperm function. As most of the manuscripts had focused on sperm motility, we could only base the RAG traffic light system on this semen characteristic.
VLs that had been studied more than once would need to have >50% of the publications report no statistically significant change or an increase in sperm motility to be placed as Green for ‘Good’, and those with >50% studies reporting a statistically significant decrease in sperm motility as Red for ‘Bad’. VLs that have equal reports of positive and negative for sperm motility or were studied only once were placed as Amber for ‘Inconclusive’.
Study checklist assessment
The reliability of the results of a semen analysis is dependent on the technical methods used to measure the different semen characteristics and authors being clear in their manuscripts which ones they used (Björndahl et al. Citation2016). We used the checklist provided by Björndahl et al. (Citation2016) to score all included manuscripts (n = 19) for the extent to which they disclosed the technical methods they used when assessing the different semen characteristics. The parameters of interest that were scored for were sperm motility, sperm vitality and sperm morphology assessments from the studies without restricting the time frame of the study publication date. We quantified the total check points outlined under each assessment criteria within the checklist and used the total number to score against each manuscript by reviewing their methodologies. The total scoring achieved for each semen characteristic was 7 for motility, 3 for vitality, and 6 for morphology. For example, manuscripts that looked at the effect of sperm motility could only get a maximum of 7 points, if they have exclusively stated following each of the sperm motility assessment criteria. It is important to note that these scores are not enough to reveal the quality of laboratory assessment but the extent to which the manuscripts disclose the WHO recommended technical methods used to assess each of these semen characteristics.
Results
A total of 56 manuscripts were identified following PubMed and Scopus searching using the Boolean terminology and the keywords selected. Following removal of duplicates (n = 19) and articles which did not meet our inclusion criteria after a full text review (n = 31), 24 manuscripts were eligible for inclusion in our review (, Supplementary Table 1). A total of 50 compounds that have been studied as VLs were identified among the 24 manuscripts (Supplementary Table 1 & 2), however this final review and analysis only focused on the OTC lubricants (n = 35) (). Only 2 manuscripts were identified as in vivo-based studies, and the remaining 22 articles were in vitro. Miller et al. (Citation1994) examined the effects of Surgilube (Non-OTC) on sperm motility and compared them both in vitro and in vivo with and without the VL. Specifically, for the in vivo experiment, participants were enrolled for a standard post-coitus test to examine differences in sperm motility with and without the use of the lubricants. The second manuscript reported secondary analyses of couples TTC in which women were surveyed over their use of VLs and examined against the endpoint of them achieving a pregnancy, defined as a positive urinary pregnancy test, or not within 6 months (Steiner et al., Citation2012).
Table 1. Key findings of 35 OTC lubricants investigated between 1972 to 2022.
The manuscripts included in our final systematic review were published between 1972 and 2022. Of the 19 in-vitro studies, most did not fully disclose the technical methods they used to assess the different semen characteristics, and there was variation in how the samples were prepared, and how parameters were defined by the included manuscripts. Sperm motility was found to be a primary parameter evaluated among the manuscripts. Sperm vitality was studied 7 times, morphology was studied once, and DNA damage was examined by 3 separate manuscripts. outlines the key findings for each of the 35 OTC compounds included against each manuscript included in the final systematic review (n = 19). 19 of the 35 OTC compounds were found to be specifically advertised and manufactured as ‘vaginal lubricants’ or ‘vaginal moisturisers’, 14 were either common household products or lotions, and the remaining 2 were manufactured as feminine hygiene cleansers. KY Jelly, PreSeed and Astroglide were identified as the top 3 studied lubricants. KY Jelly was consistently reported to decrease total or progressive sperm motility, with no observable impact on sperm DNA damage or vitality rates (). PreSeed was consistently reported to have no significant change to sperm motility, vitality, and morphology (). Whereas for Astroglide, all studies found sperm motility and viability to decrease following treatment (). The review identified common household products were also studied as lubricants, including plant-based oils (e.g. olive, peanut, canola, mustard, vegetable, safflower, and sesame), egg white, petroleum jelly, and lotions (Alpha-Keri, Keri lotion, Baby Oil, Skin lotion Searle, and Purity & Elizabeth Anne). However, it was noted that the majority were studied once, apart from olive oil, Johnson’s® Baby Oil, canola oil, and egg white where they were studied at least two times ().
Based on the evidence reported regarding the impact the VL on sperm function, the 35 lubricants were categorized using the RAG rating to facilitate whether the lubricant should or should not be recommended based on their sperm motility assessments (). Four VLs were categorized as Green under the RAG rating as over half of the published manuscripts for each lubricant reported favourable outcomes on sperm motility (i.e. PreSeed, Johnson’s® Baby Oil, canola oil, and egg white). Under the Red rating, 6 VLs (i.e. KY Jelly, Astroglide, Replens, olive oil, Yes, KY Jelly Warming) were placed since most of the published findings found detrimental impact on sperm motility following treatment. The remaining 25 VLs were placed under the Amber rating as the data appeared to be inconclusive for one lubricant (i.e. Conceive Plus) and the others had only 1 manuscript.
Table 2. RAG traffic light system of the 35 OTC lubricant categorized according to what most studies reported their findings on sperm motility.
In addition to reporting the key findings of the lubricants studied, we highlighted if the lubricant was tested against raw semen samples or a prepared sample (see ). Among the 35 OTC VLs, each were tested differently in each manuscript, either by using it as a fresh raw sample, prepared using density gradient centrifugation (DGC), or direct sperm swim-up (DSUS) preparation. 22 VLs were tested using raw semen samples across 11 different manuscripts, 19 VLs among 6 manuscripts were tested on samples after DGC preparation, and 4 VLs from 1 manuscript were tested using samples prepared with DSUS preparation.
The technical methods used to analyse the different semen characteristics were not standardized across the included manuscripts. These technical methods were analysed for conformance to the Björndahl et al. (Citation2016) checklist for reporting the results of sperm motility, vitality, and morphology assessments (). Overall, most manuscripts did not sufficiently outline the methodologies they used to assess these semen characteristics. Whilst 52.6% (10/19) cited that they followed the relevant WHO recommendations when performing the initial handling and analysis to select normozoospermic samples prior to VL incubation, only 21% (4/19) cited they used the WHO recommendations when assessing semen characteristics following the VL treatments. Of these 4 studies, only 1 outlined the technical method in full, as assessed using the Björndahl et al. (Citation2016) checklist (See ).
Table 3. Checklist of the publications looking at the OTC lubricants cross-checked against the (Björndahl et al., Citation2016) guidance when reporting technical methods used when performing a semen analysis.
Discussion
At present there are no guidelines or recommendations for HCPs and couples TTC to consult to help them choose a VL that is ‘sperm-safe’. To offer clarity on this, we have categorized all VLs identified in our literature search as Red, Amber or Green based not only on their reported effect on sperm function but also the number of manuscripts reporting these findings and how consistence their reported findings were, including how standardized their semen analysis methods were. Based on our analysis presented herein, we do not currently believe that there is sufficient evidence for a robust guidance or recommendation to be formulated. The majority of VLs were categorized as Amber due to there being an insufficient number of articles published to draw any conclusive results and undertake robust evidence synthesis, or because of heterogenous findings (i.e. Conceive Plus). The RAG rating is useful in its purpose to highlight how many manuscripts did find positive or negative outcomes of VLs against sperm motility, a very important functional parameter of the cell. Unfortunately, by having most manuscripts focus on sperm motility only, other functional parameters such as vitality, total count or concentration, morphology, the ability to fertilize a cell, or the overall function within the female reproductive tract following treatment could not be used to categorize VLs using the RAG rating. Sperm motility is known to be related to pregnancy rates (Barratt et al., Citation2011), and therefore any compound that lowers sperm motility may impact the success of couples actively trying to conceive. However, if a lubricant has no impact on sperm motility this doesn’t necessarily mean that a lubricant can be labelled as ‘sperm-safe’ as it has been well noted that there are many other factors (for example, the ability of sperm to undergo the acrosome reaction or sperm hyperactivation) that impact the ability of a sperm to fertilize an oocyte. Henceforth, for VLs with no obvious impact on sperm motility, (i.e. PreSeed) further tests on their impact on other functional parameters of sperm are required before we can be certain whether they are fully safe to be used by couples actively trying to conceive. Furthermore, to the best of our knowledge, there is no published manuscript that has assessed whether the impact of lubricants known to decrease sperm motility can be reversed making it difficult at this stage to confidently label any VL as ‘sperm-safe’.
As mentioned previously, the reliability of the results of a semen analysis are dependent on the technical methods used to assess the different semen characteristics, with the WHO recommendations providing up to date evidence-based recommendations to help laboratories standardize these methods. Interestingly, only one manuscript fully outlined the technical methods that they followed when assessing sperm motility (Mackenzie & Gellatly, Citation2019) with all other manuscripts only providing partial information regarding the technical steps they followed, or simply stating that they followed relevant WHO recommendations without providing specific details. For the latter manuscripts, we are currently not able to fully assess the quality of their semen analysis results and therefore the reliability of their results. Inconsistent outcome reporting and definitions of these outcomes makes the evidence synthesis challenging and a meta-analysis not possible at this stage, limiting the utility of these studies to inform clinical practice, a not uncommon finding in the field of male reproductive health (Rimmer et al., Citation2022). When reviewing the manuscripts, most focused on the impact of VLs on sperm motility in washed and prepared sperm, with most of these manuscripts detailing different experimental approaches (i.e. lubricant concentration and incubation time). In vivo sperm are most likely to encounter a VL when they are in semen, therefore a comparison of a VLs impact on sperm function in semen and washed and prepared samples is required in the future. Mortimer et al. (Citation2013) recommended that in addition to performing a basic semen analysis to assess whether a compound is ‘sperm-safe’, further assays to measure a compound's impact on other markers of sperm function not assessed in a basic semen analysis should also be performed prior to labelling anything as ‘sperm-safe’ of sperm. Many manuscripts did not report on rates of conception or pregnancy outcomes, likely to be the primary motivation a couple are attending a fertility clinic, which limits these studies utility to inform clinical practice.
These findings call for concern since most of the manuscripts focused on the effects of VLs on sperm motility only, with the majority of them failing to outline the technical steps they used when assessing sperm motility, limiting our ability to judge the reliability of the results of all the other manuscripts (Björndahl et al., Citation2016; Vasconcelos et al., Citation2022; World Health Organization, Citation2021). Furthermore, some of the publications reported the sperm motility data with SMI values or a sperm progression rating system for either the impact on motility or vitality following lubricant treatment (Goldenberg & White, Citation1975; Markram et al., Citation2022; Soriano et al., Citation2021; Vargas et al., Citation2011).
Using SMI values or a sperm progression rating system is an alternative method to reporting sperm motility data, however the lack of reporting of the essential steps required when performing a standard motility analysis is not explained. For vitality assessments, there was noted similar compliance to reporting of the criteria as there was for motility assessments, with 1 out of 7 studies reporting 3 out of 3 criteria (Agarwal et al., Citation2013). Whilst progressive motility has both biological and clinical importance for in vivo and in vitro conception (Barratt et al., Citation2011; Björndahl et al., Citation2010), other aspects of sperm function also influence whether a progressively motile sperm is able to fertilize an oocyte (ability to undergo the acrosome reaction, sperm hyperactivation etc) and therefore should be taken more into account.
When reviewing the compositions of the OTC VLs tested, for some of them there were discrepancies between the ingredients noted by the manufacturer and those reported in the manuscripts. The differences were either missing or new compounds reported, or differently ordered lists. Products’ ingredients can change over time by the manufacturers, and whilst there is no present legislation preventing products from being altered, they still must adhere to the current regulations of different countries for accurately reporting their ingredients lists (European Commission, Citation2019; Medicines and Healthcare Products Regulatory Agency Delivery Plan 2021–2023, (Citation2022); Office for Product Safety and Standards, Citation2021). Therefore, if we were to assume that at the time of publication and study of these lubricants the ingredients list was correct, this may provide additional explanation as to why there is such heterogeneity among the published data of the VL impact on sperm function. One example would be KY Jelly, a lubricant that was studied since 1972, yet 7 out of 10 studies found detrimental and negative effects on sperm motility, while the other 3 did not report statistically significant impacts, or the differences were non-significant compared to the control of the study for sperm motility. As this product has been commercially available for several decades, its formulation may have changed over time, and therefore changes to the composition of KY Jelly may explain slight difference in the results described in these different studies. For that reason, future studies attempting to demonstrate lubricants impact on sperm function should consider quantifying the exact ingredients and concentrations of the testing product to clearly outline if the reported ingredients are accurate.
Conclusions
Presently, there is insufficient evidence to formulate a robust guidance or recommendation for HCPs and couples regarding the impact of VLs on sperm function. Based on our results, we can only recommend and categorize lubricants based on their reported impact on sperm motility which is restrictive when considering the overall safety of any product, particularly for couples who are actively trying to conceive, as many other factors in addition to sperm motility can impact sperm’s ability to fertilize an oocyte. The current recommendations should be taken with caution as the many of the included manuscripts did not fully illustrate that they performed the standardized method of assessing sperm motility, and the different manuscripts did not standardize the VL concentration or incubation time making comparison of manuscripts and drawing conclusions difficult. Despite what some of the identified studies may state regarding KY Jelly or Replens being ‘spermo-toxic’ based on their sperm motility assessments (Soriano et al., Citation2021; Vargas et al., Citation2011), further research is required and appropriate assays to be performed to understand if the product is truly ‘spermo-toxic’ (Mortimer et al., Citation2013). Furthermore, in the case of VLs shown not to impact sperm function further tests are required to assess their impact on other factors known to be important for fertilization, such as the sperm’s ability to successfully complete the acrosome reaction, sperm hyperactivation, and other markers of sperm capacitation. The results reported, herein, are important as they allow us to gauge the gaps and shortcomings in current data regarding the impact of VLs on sperm function revealing clear evidence-based recommendations to guide future research.
Authors’ roles
EG and SAG performed the initial study design. EG performed the original data collection and data analysis as part of her MSc research project under School of Medicine, University of Dundee. The initial draft of the manuscript was written by EG and SAG, followed by discussions and further drafting by MPR. All authors contributed to the writing and editing of the final draft of the manuscript.
Supplemental Material
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Download MS Word (16.5 KB)Acknowledgements
The authors would like to thank Professor Christopher Barratt (School of Medicine, University of Dundee) for his feedback on the article.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Data availability statement
The data underlying this article will be shared on reasonable request to the corresponding author.
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