Abstract
Objective
To assess the extent to which lubricant use during intercourse is associated with time-to-pregnancy (TTP).
Design
Prospective cohort study.
Setting
Denmark and North America.
Population
6,467 women aged 18-49 years who were not using contraception or fertility treatment.
Methods
We pooled data from two ongoing prospective cohort studies of pregnancy planners in Denmark (2011-2017) and North America (2013-2017). Female participants completed bimonthly questionnaires for 12 months or until reported pregnancy. After restricting to women without a history of infertility who had been trying to conceive for ≤6 cycles at enrollment, 6,467 women were retained for analysis. Self-reported lubricant use was categorized as water-based/not pH balanced, water-based/pH balanced (“fertility friendly”), silicone-based, oil-based, or a combination of these. We used proportional probabilities models to calculate fecundability ratios (FRs) and 95% confidence intervals (CIs) for the association between lubricant use and fecundability after adjusting for cohort and socio-demographic and lifestyle factors.
Main Outcome Measures
Fecundability.
Results
At baseline, 17.5% of participants reported use of lubricants, most commonly water-based/not pH balanced (11.4%). Compared with non-use of lubricants, FRs were 1.02 (95% CI: 0.93-1.11) for water-based/not pH balanced lubricant use, 1.01 (95% CI: 0.86-1.18) for water-based/pH balanced (“fertility friendly”) lubricant use, 1.23 (95% CI: 0.94-1.61) for oil-based lubricant use, and 1.27 (95% CI: 0.93-1.73) for silicone-based lubricant use. Associations between oil-based lubricant use and fecundability were inconsistent across subgroups of study cohort, age, parity, and intercourse frequency.
Conclusions
Lubricant use was not associated with reduced fecundability in the preconception cohorts of pregnancy planners studied
Keywords: lubricant, fertility, cohort, epidemiology, fecundability
Introduction
Female sexual arousal is a complex process beginning with neural signaling and ending with vaginal lubrication.1 Low estrogen levels can disrupt this process and result in vaginal dryness and pain during intercourse.1 Vaginal lubricants are used during intercourse to increase satisfaction.2, 3 In a nationally-representative sample of U.S. women, 65.5% reported using a commercially-available lubricant during the past year and 20.0% reported using a commercially-available lubricant during the past month.3 Occasional vaginal dryness is reported by most couples trying to conceive,4 perhaps because of higher intercourse frequency,5 increased stress, and the lack of spontaneity often associated with timed intercourse. One study found that 28.6% of couples attempting to conceive reported occasional use of lubricants during intercourse and 14.3% reported frequent use.5
The association between lubricant use and fecundability has not been studied extensively. In vitro studies have found that exposure to common water-based,6–10 oil-based,11 or silicone-based12 lubricants was associated with reduced sperm motility and viability, with adverse effects varying by type of water-11, 12 or oil-based8–10, 13 lubricant and with increasing lubricant concentration13, 14 or exposure time.8–10 In these laboratory studies, adverse effects of oil-8, 9, 13 and silicone9-based lubricants were generally absent when semen samples were exposed for <5 minutes to oil-based lubricants and for <30 minutes to silicone-based lubricants. The water-based lubricant Pre-Seed® is marketed as a fertility-friendly lubricant because it has the same pH as cervical fluid. Pre-Seed® is associated with minimal or no adverse effects on semen parameters studied in vitro.12, 15–17
The association between lubricant use and fecundability has been examined in only one epidemiologic study, a prospective time-to-pregnancy (TTP) cohort study of 296 women aged ≥30 years. Contrary to findings from in vitro semen analyses, lubricant use was not associated with fecundability, even when used during the fertile window.5 Small study size precluded the analysis of different types of lubricants.5 In the present prospective cohort study of Danish and North American couples, we examine the association between use of lubricants, and its specific types, and fecundability.
Methods
Study population
To enhance precision, data from two ongoing prospective preconception cohort studies were pooled in this analysis. In Denmark, the Snart Foraeldre (SF) study (August 2011-present) recruits women aged 18-49. In the United States and Canada, Pregnancy Study Online (PRESTO) (June 2013-present) recruits women aged 21-45.18 In both cohorts, eligible participants are in a relationship with a male partner, trying to conceive, and not currently pregnant, using contraception or fertility treatments.
SF and PRESTO have nearly identical study designs. Data are collected via online questionnaires. At baseline, women report information about demographics, behaviors, lifestyle factors, and medical history. They complete follow-up questionnaires every 2 months until reported pregnancy, initiation of fertility treatment, loss to follow-up, or 12 months, whichever occurs first. Over 80% of enrolled participants have completed at least one follow-up questionnaire.
The Danish Data Protection Board (November 28, 2017; Reference: H-28795) and the Boston Medical Center Institutional Review Board (March 17, 2017, Reference: H-31848) approved the data collection tools and overall study protocols, and participants provided online informed consent. Funding for this study was provided by the National Institutes of Health (R01-HD060680, R01-HD086742, R21-HD050264, R21-HD072326, and T32-HD052458). The funding agency did not play a role in the conduct of research or manuscript preparation.
Assessment of lubricant use
At baseline, women in both cohorts reported whether they typically used a lubricant during intercourse (yes vs no). In PRESTO, past-month users reported the name(s) of the lubricant(s) they used (check all that apply) and frequency of use (“occasionally”, “frequently”, “all the time”). A list of common lubricants was provided, including KY Jelly®, Astroglide®, Silk®, Wet®, Replens®, Pre-Seed®, Vaseline®, FemGlide®, baby oil, and olive, vegetable, or other plant- or animal-based oil. An open-ended text field was also provided for “other type,” and women could report “don’t know” as an option. In SF, women were asked to indicate the name of the lubricant(s) they used most frequently in an open-ended text field. In PRESTO, information about past-month lubricant use was elicited on each follow-up questionnaire.
Assessment of covariates
On the baseline questionnaire, female participants reported detailed data on demographics (age, race/ethnicity); socioeconomic position (education, income, marital status); lifestyle factor, anthropometrics; reproductive, and medical history; and characteristics of their male partners (i.e., age, smoking, height, weight, and education). Females reported on the frequency of intercourse and methods used to improve one’s chances of conception (e.g., charting menses, ovulation testing, cervical fluid monitoring, recording of basal body temperature) on the baseline and follow-up questionnaires. Body mass index was calculated as weight (kg)/height (m)2.
Assessment of pregnancy and cycles at risk
At baseline, female participants reported their date of last menstrual period (LMP), typical menstrual cycle length, and number of menstrual cycles of pregnancy attempt time since discontinuing contraception. On follow-up questionnaires, female participants reported their LMP date and pregnancy status. Cycles at risk were calculated as (reported menstrual cycles of attempt time at study entry) + [(LMP date from most recent follow-up questionnaire - date of baseline questionnaire)/menstrual cycle length] + 1. Women contributed cycles to the analysis until conception, commencement of fertility treatments, loss-to-follow-up, or 12 cycles, whichever occurred first.
Exclusions
We excluded participants if they reported implausible menstrual cycle information (i.e., LMP date >6 months before the baseline questionnaire, no pregnancy and no new LMP over follow-up, or reported baseline LMP date was after the baseline questionnaire completion date), if they had been trying to conceive for >6 cycles at study entry, or if they had previously tried to conceive for ≥12 months without becoming pregnant (i.e. history of infertility). Figure 1 displays the number of women excluded from each study cohort. The final analytic population included 2,588 women from SF and 3,879 women from PRESTO, for a total of 6,467 women.
Figure 1.
Flow chart of enrollment and exclusions, Snart Foraeldre and PRESTO (N=8,964), 2011-2017.
Data analysis
Lubricants were categorized by their base and pH balance. The base was taken as the first ingredient listed on the product label (water, oil, or silicone). Water-based lubricants were then divided into two categories: those engineered to match the pH of cervical fluid (7.0),19 referred to as water-based/pH balanced (“fertility friendly”); and those that are water-based but not pH balanced to the cervical fluid. Women who used more than one type of lubricant were analyzed separately. Mutually-exclusive categories included water-based/not pH balanced; water-based/pH balanced (“fertility friendly”); silicone-based; oil-based; and mix of types.
Life table methods were used to compute the cumulative proportion of pregnancy during 12 cycles of follow-up. We used proportional probabilities regression models to estimate fecundability ratios (FRs) and 95% confidence intervals (CIs).20 The FR is the average per-cycle probability of conception comparing lubricant users to non-users; FRs <1 indicate longer TTP among exposed than unexposed. The proportional probabilities model adjusts for observed cycle number, accounting for declining average fecundability among couples over analysis time.20 We used the Andersen-Gill data structure to account for differences in attempt time at enrollment (0-6 cycles) and to reduce bias from left truncation.21–23 For example, if a woman entered the study with 1 cycle of attempt and conceived during the 3rd cycle, she contributed cycles 2 and 3 to the analysis. We used the weighted copy method to minimize convergence issues produced by the regression model.24
We identified potential confounders a priori using a directed acyclic graph. These a priori variables included study cohort (SF versus PRESTO), age (<25, 25-29, 30-34, 35-39, ≥40 years), education (≤12, 13-15, 16, ≥17 years), household income (< versus ≥ 50,000 U.S. dollars/300,000 Danish kroners per year), non-Hispanic white (yes/no), BMI (<18.5, 18.5-24, 25-29, ≥30 kg/m2), cigarette smoking (current, past, never), and doing something to improve chances of conception (e.g. timing intercourse around the fertile window, monitoring consistency of cervical mucus, testing for ovulation) (yes versus no). Results were examined with and without adjustment for intercourse frequency (<1, 1, 2-3, ≥4 times per week), which is a potential causal intermediate.25, 26
Secondary analyses, conducted only in PRESTO due to data availability, examined frequency of use (“occasionally”, “frequently”, “all the time”), and updated lubricant use over time based on reports from bimonthly follow-up questionnaires.
We examined effect measure modification by age (<30 versus ≥30 years),27 BMI (<30 versus ≥30 kg/m2),28 and parity (0 versus ≥1 birth)29 because natural vaginal lubrication may vary across these subgroups. We stratified our analyses by cohort (PRESTO versus SF) to account for differences in exposure assessment. We also stratified by pregnancy attempt time at study entry (0-2 versus 3-6 cycles) and intercourse frequency (<2 versus ≥2 times per week).
Missing data for covariates and exposure ranged from 0.5% (education) to 2.7% (lubricant type); there were no missing data for age. Pregnancy status was missing for 12.2% of couples. We imputed missing values for exposure, covariates, and outcome using PROC MI to create five imputed datasets. We used PROC MIANALYZE to combine coefficient and standard error estimates.30
Results
Over the study period, 76.3% of couples achieved pregnancy (PRESTO 72.0%, SF 82.7%). Lubricants were used by 17.5% of participants; 11.6% of SF participants and 21.4% of PRESTO participants reported lubricant use (Table 1). Participants most often used water-based/not pH balanced (11.4%), followed by water-based/pH balanced (“fertility friendly”) (3.9%), oil-based (1.1%), and silicone-based (0.6%) lubricants. Only 0.6% of participants used more than one type of lubricant. At study entry, users and non-users of lubricants had similar mean pregnancy attempt times (1.9 cycles vs. 2.0 cycles) and the prevalence of lubricant use was similar for women with shorter vs. longer attempt times (1 cycle: 17.8% vs. 6 cycles: 18.2%).
Table 1.
Baseline characteristics of pregnancy planners by type of lubricant use, Snart Foraeldre and PRESTO (N=6,467), 2011-2017.
| Non-user | User | Water-based/not pH balanced | Water-based/pH balanced | Silicone-based | Oil-based | Mix of types | |
|---|---|---|---|---|---|---|---|
| Number of participants, N (%) | 5,337 (82.5) | 1,130 (17.5) | 737 (11.4) | 249 (3.9) | 37 (0.6) | 69 (1.1) | 38 (0.6) |
| Snart Foraeldre, N (%) | 2,288 (42.7) | 300 (26.6) | 233 (31.6) | 13 (5.7) | 27 (71.5) | 16 (24.2) | 11 (34.7) |
| PRESTO, N (%) | 3,049 (57.3) | 830 (73.5) | 504 (68.4) | 236 (94.3) | 10 (28.5) | 53 (75.8) | 27 (65.3) |
| Pregnancy attempt time at study entry (cycles), mean | 2.0 | 1.9 | 1.7 | 2.7 | 1.1 | 1.6 | 2.1 |
| Age (years), % | |||||||
| <25 | 13.5 | 10.3 | 11.5 | 8.4 | 5.4 | 7.3 | 7.9 |
| 25-29 | 41.6 | 41.6 | 41.8 | 39.0 | 54.1 | 44.9 | 36.8 |
| 30-34 | 33.3 | 38.7 | 38.4 | 42.2 | 35.1 | 34.8 | 31.6 |
| 35-39 | 10.2 | 8.9 | 7.9 | 9.6 | 5.4 | 11.6 | 21.1 |
| ≥40 | 1.4 | 0.6 | 0.4 | 0.8 | 0.0 | 1.5 | 2.6 |
| Male partner’s age (years), mean | 31.3 | 31.3 | 31.2 | 31.2 | 30.9 | 31.7 | 32.3 |
| Non-Hispanic white, % | 91.1 | 90.3 | 91.7 | 87.7 | 94.7 | 86.2 | 81.3 |
| Annual household income <50,000 USD/300,000 DKK per year), % | 18.0 | 14.6 | 15.8 | 13.1 | 6.2 | 13.2 | 10.0 |
| <College degree, % | 22.6 | 19.4 | 18.9 | 23.0 | 13.8 | 18.8 | 15.8 |
| BMI (kg/m2), mean | 25.7 | 25.4 | 25.3 | 25.8 | 23.1 | 25.4 | 24.9 |
| Past smoker, % | 19.1 | 16.9 | 16.3 | 17.5 | 25.7 | 16.0 | 15.6 |
| Current smoker, % | 8.7 | 4.8 | 5.4 | 4.4 | 6.5 | 4.1 | 0.0 |
| Parous, % | 29.7 | 25.2 | 27.2 | 19.5 | 19.8 | 26.8 | 18.8 |
| Gravid, % | 46.5 | 40.9 | 40.7 | 43.3 | 36.0 | 36.5 | 34.8 |
| Intercourse frequency <1 time/week, % | 17.4 | 21.7 | 24.1 | 14.7 | 27.4 | 20.3 | 27.4 |
| Intercourse frequency ≥4 time/week, % | 17.9 | 13.4 | 12.6 | 15.2 | 11.5 | 14.6 | 11.8 |
| Doing something to improve chances of conception, % | 73.3 | 76.8 | 70.5 | 96.2 | 68.2 | 87.6 | 59.7 |
USD=U.S. dollars, DKK=Danish kroner
All characteristics except for age are age-standardized to the cohort at baseline.
Lubricant use was positively associated with household income and educational attainment. Lubricant users had less frequent intercourse than non-users. SF participants were more likely than PRESTO participants to use silicone-based lubricants and less likely to use water-based/pH balanced lubricants. Compared with all other participants, users of silicone-based lubricants were more likely to have a college education, higher household income, and lower BMI. Users of water-based/pH balanced lubricants had the longest attempt time at study entry (2.7 cycles) and were less likely to have a college degree than users of other types of lubricants or non-users. Women who used more than one type of lubricant were older and less likely to be non-Hispanic white compared with women who used a single type (Table 1).
FRs for lubricant use compared with non-use were 1.02 (95% CI: 0.93-1.11) for water-based/not pH balanced lubricants, 1.02 (95% CI: 0.93-1.12) for water-based/pH balanced lubricants, 1.27 (95% CI: 0.93-1.73) for silicone-based lubricants, 1.23 (95% CI: 0.94-1.61) for oil-based lubricants, and 1.18 (95% CI: 0.79-1.77) for use of more than one type of lubricant (Table 2). Results were similar with and without adjustment for intercourse frequency.
Table 2.
Lubricant use and fecundability among pregnancy planners, Snart Foraeldre and PRESTO (N=6,467), 2011-2017.
| Type of Lubricant | No. of Cycles | No. of Pregnancies | Adjusted FR (95% CI)a | Adjusted FR (95% CI)b |
|---|---|---|---|---|
| Non-user | 20,135 | 3,335 | Reference | Reference |
| Any lubricant | 4,203 | 724 | 1.06 (0.99-1.14) | 1.04 (0.97-1.12) |
| Water-based/not PH balanced | 2,840 | 481 | 1.02 (0.93-1.11) | 1.02 (0.93-1.11) |
| Water-based/pH balanced | 914 | 143 | 1.11 (0.95-1.30) | 1.01 (0.86-1.18) |
| Silicone-based | 107 | 31 | 1.35 (0.99-1.84) | 1.27 (0.93-1.73) |
| Oil-based | 200 | 43 | 1.31 (1.01-1.71) | 1.23 (0.94-1.61) |
| Mix of types | 142 | 26 | 1.07 (1.72-1.60) | 1.18 (0.79-1.77) |
FR=fecundability ratio
Models adjusted for cohort.
Models adjusted for cohort, age, education, non-Hispanic white, household income, BMI, smoking, intercourse frequency, and doing something to improve chances of conception.
Oil-based lubricant use was associated with increased fecundability among PRESTO but not appreciably associated among SF participants (Table 3). Among participants in both cohorts, oil-based lubricant use was associated with increased fecundability among users who were older, nulliparous, or had less frequent intercourse compared with non-users. There was little association between use of oil-based lubricant and fecundability among participants who were younger, parous, or had more frequent intercourse. Parous women who used water-based/pH balanced “fertility friendly” lubricants had slightly reduced fecundability compared with non-users (Table 3). Results were consistent across strata of attempt time at study entry and BMI (data not shown).
Table 3.
Lubricant use and fecundability among pregnancy planners stratified by age, parity, and cohort (Snart Foraeldre and PRESTO) (N=6,467), 2011-2017.
| Exposure | No. of Cycles | No. of Pregs | Adjusted FR (95% CI) a | Adjusted FR (95% CI)b | No. of Cycles | No. of Pregs | Adjusted FR (95% CI) a | Adjusted FR (95% CI) b |
|---|---|---|---|---|---|---|---|---|
|
PRESTO
|
Snart Foraeldre
|
|||||||
| Non-user | 12,059 | 1,797 | Reference | Reference | 8,076 | 1,538 | Reference | Reference |
| Any lubricant | 3,243 | 496 | 1.01 (0.92-1.10) | 0.98 (0.89-1.07) | 960 | 228 | 1.18 (1.04-1.34) | 1.16 (1.02-1.31) |
| Water-based/not PH balanced | 2,075 | 303 | 0.95 (0.85-1.06) | 0.95 (0.84-1.06) | 765 | 178 | 1.14 (0.99-1.32) | 1.13 (0.97-1.31) |
| Water-based/pH balanced | 875 | 135 | 1.08 (0.92-1.27) | 0.97 (0.82-1.14) | 39 | 8 | 1.53 (0.82-2.83) | 1.44 (0.78-2.67) |
| Silicone-based | 34 | 9 | 1.28 (0.71-2.33) | 1.19 (0.66-2.15) | 73 | 22 | 1.38 (0.96-1.98) | 1.28 (0.89-1.83) |
| Oil-based | 143 | 32 | 1.40 (1.03-1.89) | 1.28 (0.95-1.74) | 57 | 11 | 1.11 (0.66-1.87) | 1.07 (0.63-1.80) |
| Mix of types | 116 | 17 | 0.92 (0.59-1.44) | 1.06 (0.68-1.66) | 26 | 9 | 1.44 (0.68-3.01) | 1.41 (0.67-3.00) |
|
| ||||||||
|
Age <30 years
|
Age ≥30 years
|
|||||||
| Non-user | 10,835 | 1,854 | Reference | Reference | 9,300 | 1,481 | Reference | Reference |
| Any lubricant | 2,118 | 392 | 1.10 (0.99-1.21) | 1.08 (0.98-1.20) | 2,085 | 332 | 1.02 (0.92-1.14) | 1.00 (0.90-1.12) |
| Water-based/not PH balanced | 1,436 | 263 | 1.06 (0.94-1.20) | 1.06 (0.94-1.20) | 1,404 | 218 | 0.97 (0.85-1.10) | 0.97 (0.85-1.11) |
| Water-based/pH balanced | 441 | 76 | 1.18 (0.95-1.46) | 1.11 (0.89-1.37) | 473 | 67 | 1.05 (0.84-1.31) | 0.92 (0.73-1.15) |
| Silicone-based | 67 | 17 | 1.21 (0.79-1.87) | 1.19 (0.77-1.83) | 40 | 14 | 1.58 (1.03-2.44) | 1.44 (0.93-2.23) |
| Oil-based | 115 | 22 | 1.14 (0.79-1.66) | 1.04 (0.72-1.52) | 85 | 21 | 1.55 (1.07-2.23) | 1.55 (1.07-2.22) |
| Mix of types | 59 | 14 | 1.24 (0.72-2.14) | 1.32 (0.76-2.30) | 83 | 12 | 0.95 (0.55-1.62) | 1.09 (0.63-1.88) |
|
| ||||||||
|
Nulliparous
|
Parous
|
|||||||
| Non-user | 15,024 | 2,238 | Reference | Reference | 5,111 | 1,097 | Reference | Reference |
| Any lubricant | 3,282 | 516 | 1.08 (0.99-1.18) | 1.06 (0.97-1.16) | 921 | 208 | 1.05 (0.92-1.19) | 1.01 (0.88-1.15) |
| Water-based/not PH balanced | 2,174 | 329 | 1.02 (0.91-1.14) | 1.03 (0.92-1.15) | 555 | 152 | 1.02 (0.88-1.19) | 1.01 (0.87-1.17) |
| Water-based/pH balanced | 754 | 115 | 1.17 (0.98-1.39) | 1.07 (0.90-1.28) | 160 | 28 | 0.99 (0.70-1.41) | 0.82 (0.58-1.16) |
| Silicone-based | 98 | 24 | 1.28 (0.88-1.87) | 1.20 (0.83-1.75) | 9 | 7 | 2.04 (1.40-2.97) | 1.88 (1.27-2.80) |
| Oil-based | 147 | 31 | 1.42 (1.04-1.94) | 1.34 (0.98-1.85) | 53 | 12 | 1.08 (0.67-1.74) | 0.95 (0.60-1.52) |
| Mix of types | 109 | 17 | 1.06 (0.66-1.68) | 1.13 (0.70-1.82) | 33 | 9 | 1.11 (0.50-2.47) | 1.33 (0.57-3.11) |
FR=fecundability ratio
Models adjusted for cohort.
Models adjusted for cohort, age, education, non-Hispanic white, household income, BMI, smoking, intercourse frequency, and doing something to improve chances of conception.
Frequency of lubricant use was ascertained in PRESTO only. While there was little overall association between frequency of lubricant use and fecundability, we observed a dose-response association between frequency of oil-based lubricant use and fecundability: women using oil-based lubricants “all the time” had an FR of 1.89 (95% CI: 1.26-2.82). Likewise, women using water-based/pH balanced lubricants “all the time” had an FR of 1.26 (95% CI: 0.99-1.60). The small number of PRESTO silicone-based lubricant users precluded interpretation of results by timing and frequency (data not shown).
In time-varying analyses among PRESTO participants, lubricant use remained relatively consistent over follow-up; 89.5% of PRESTO participants who reported lubricant use at baseline also reported lubricant use on their last follow-up questionnaire, while 10.5% of baseline users discontinued use. Results from time-varying analyses were consistent with the time-invariant results (data not shown).
Discussion
Main Findings
In this population of 6,467 female pregnancy planners without a history of infertility, there was no indication of strong adverse effects of lubricant use. We found small increases in fecundability among women who used oil- or silicone-based lubricants after adjusting for demographics and lifestyle factors. However, results for silicone-based lubricants were imprecise and results for oil-based lubricants were inconsistent across subgroups.
Strengths and limitations
This study has several limitations. Precision was limited by the small number of silicone and oil-based lubricant users, and the collection of frequency and time-varying use only in PRESTO. Further, lubricant use was recalled and is subject to error. Steiner and colleagues found moderate concordance between baseline self-report and daily diary tracking (kappa=0.46) of lubricant use; a minority of the participants who reported never using lubricants at baseline recorded occasional and frequent use in their diaries (26%).5 The phrasing of questions in the present analysis varied across cohorts. PRESTO participants were asked about any lubricant use during the past month (using a checklist) and frequency of use, while SF participants were asked about lubricants they used frequently using an open-ended question. Additionally, we did not ask specifically about lubricant use during the fertile window. Any exposure misclassification in this prospective study is likely non-differential, biasing estimates towards the null. Pregnancy attempt time may have also been misclassified in the present study. If reporting accuracy varies by lubricant use, our results may be biased in either direction.31 While our results did not change substantially after adjusting for measured potential confounders, residual confounding by unmeasured or unknown confounders is possible. Lastly, approximately 18% of participants were lost-to-follow-up before study completion; because follow-up was similar among users and non-users of lubricants, selection bias is unlikely.
This is the largest study of lubricant use and fecundability to date and the first to evaluate whether type of lubricant affects fecundability. Lubricant data were ascertained prospectively relative to fertility, reducing potential for differential misclassification of exposure and selection bias. Finally, we collected detailed covariate information, allowing control for multiple potential confounders, including age and education.
Interpretation
Our results agree with the sole previous study that examined the relation between lubricant use and fecundability.5 Our results, and those from the study by Steiner et al.,5 conflict with laboratory data showing adverse effects of lubricants on semen parameters.6–14 Immediately following ejaculation, semen coagulates to reduce loss from the vagina and to protect sperm from the acidic vaginal pH;32 although semen re-liquefies after about 20 minutes,32 the first ejaculated sperm pass through the cervix in as little as one minute after ejaculation.33–35 In vitro studies examine semen parameters after liquefaction and expose sperm to lubricants for longer than would occur during natural reproduction. Laboratory studies primarily examined post-liquefaction semen parameters after 5 minutes7, 8, 10, 12, 13, 15 to 24 hours of exposure,17 with results that varied according to the duration.8–10
Use of oil-based lubricants was associated with slightly increased fecundability among PRESTO participants, with stronger results among couples who reported always using oil-based lubricants. Oil-based lubricant use was not appreciably associated with fecundability among SF participants. It is possible that women in SF and PRESTO use different types of oil-based lubricants; in studies of semen parameters after oil-based lubricant exposure, results varied by type of oil,8–10, 13 with one study finding sperm hyperactivation after exposure to mustard oil.10 If couples in Denmark and North America use different types of oils, this could account for the inconsistent results across cohorts. Our results may also be influenced by residual and unmeasured confounding. PRESTO couples using oil-based lubricants may be more health-conscious than non-users and, as a result, less likely to have poor diets or be exposed to environmental toxicants, which are more common in North America.36–38
While the small number of users of silicone-based lubricants hampered precision, our results indicate a modest but consistent increase in fecundability among users of such lubricants. Research examining semen parameters after exposure to silicone-based lubricants is sparse;9, 12 one study examined varied lengths of exposure and found reduced motility after 60 minutes, but no meaningful difference after 1, 15, and 30 minutes of exposure.
Overall, we found that water-based/pH balanced (“fertility friendly”) lubricants were not associated appreciably with fecundability. Compared with non-users, fecundability was slightly reduced among users of water-based/pH balanced lubricants who were parous. Although we excluded women with a history of infertility to reduce potential for reverse causation, parous women with suspected subfertility may have chosen to use water-based/pH balanced (“fertility friendly”) lubricants.
Conclusions
Among Danish and North American pregnancy planners, lubricant use was not associated with reduced fecundability. Moreover, contrary to expectation, water-based/pH balanced (“fertility friendly”) lubricants were not associated with increased fecundability. If confirmed in subsequent studies, these results suggest that couples should use the lubricant that best suits their needs while trying to conceive.
Acknowledgments
We are grateful Michael Bairos for development and maintenance of the PRESTO technological infrastructures.
Funding: National Institute of Child Health and Human Development (R01-HD060680, R01-HD086742, R21-HD050264, R21-HD072326, and T32-HD052458)
Funding
This study was supported through funds provided by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health (R01-HD086742, R03-HD090315, R21-HD072326, T32-HD052458).
Footnotes
Disclosures
The authors have no conflicts of interest to disclose. Completed disclosure of interest forms are available to view online as supporting information.
Author Contributions: K.A.M. performed data management, analyses and drafted the manuscript. K.A.H. performed data management, analyses and assisted with compilation of the manuscript. L.A.W. planned and implemented the PRESTO & SF studies, assisted with data analysis, and oversaw analytic decision-making and compilation of the manuscript. K.J.R., E.M.M., E.E.H., and H.T.S. planned and implemented the PRESTO & SF studies and assisted with analytic decision-making and compilation of the manuscript. A.Z.S. and T.M.S. assisted with exposure classification, provided clinical guidance on the interpretation of study results, and assisted with compilation of the manuscript.
Details of Ethical Approval
The Danish Data Protection Board (November 28, 2017; Reference: H-28795) and the Boston Medical Center Institutional Review Board (March 17, 2017, Reference: H-31848) approved the data collection tools and overall study protocols, and participants provided online informed consent.
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