An evaluation of the pre-ejaculate in coitus interruptus
Awarded 2019
Complex Family Planning Fellowship Research
Jasmine Patel, MD
University of Southern California

According to the National Survey on Family Growth, 8% of women relied solely on coitus interruptus, or withdrawal, in 2014 for pregnancy prevention. Although survey revisions were introduced, this prevalence represented an increase from 5% in 2008. As patients increasingly report the use of withdrawal, providers need to be knowledgeable about the method to counsel patients accurately and without bias. However, provider recommendations against the use and patients’ successful experiences are inconsistent.
Trussell et al. estimate that 4% of withdrawal-using women become pregnant during the first year of perfect use, estimating a modest risk of pregnancy-related to sperm in the pre-ejaculate. However, SR Killick also described an in vitro study where 59% (16/27) of individuals produced consistently azoospermic pre-ejaculate samples. We will expand on this work by examining clinical and behavioral factors that may be associated with the presence or absence of sperm in the pre-ejaculate. We will recruit about 30 couples who are willing to use withdrawal to characterize via survey, their knowledge of, attitudes towards, and experience with withdrawal for pregnancy prevention. Specifically, we will query their perceived pregnancy risk, willingness to accept an unintended pregnancy, and ability to predict “successful” use of withdrawal. The male and female members of each couple will complete surveys individually.
Following the survey, couples will be invited to participate in in-vitro and in-vivo experiments to characterize their use of withdrawal. To evaluate the presence of sperm in the pre-ejaculate in vitro, the men will collect their pre-ejaculate in a Petri dish, using methods similar to Killick et al, and also collect their ejaculate in a separate Petri dish. Samples that were considered “perfect” will only be analyzed. The pre-ejaculate will be analyzed for the concentration of prostate-specific antigen (PSA) and sperm. Pre-ejaculate markers will be compared to those of the individual’s ejaculate, to verify that the first specimen was truly pre-ejaculate. Multiple samples will be obtained from each individual to examine sampling consistency and permit both inter- and intra- individual variation among pre-ejaculate specimens.
We will conduct an in-vivo experiment using PSA, a robust biomarker for determining the presence of prostatic fluid in the vagina. With each episode of intercourse using withdrawal, a vaginal swab will be collected pre-coitally and post-withdrawal. The vaginal samples will then be tested for the presence of PSA; its absence might be indicative of an episode of withdrawal conferring a low risk of pregnancy. This data will be analyzed against the male partner’s in-vitro findings of sperm in the pre-ejaculate for concordance. Biomarkers will be compared against individual demographics and survey responses in bivariate analyses to determine factors potentially influencing the contraceptive efficacy of withdrawal. In summary, this project seeks to provide an evaluation of “perfect-use” of coitus interruptus.