Using marijuana does not reduce chances of getting pregnant

Marijuana use by either men or women does not lower chances of getting pregnant, according to a new study led by Boston University School of Public Health (BUSPH) researchers. Marijuana is one of the most widely used recreational drugs among individuals of reproductive age. Previous studies have examined the effects of marijuana use on reproductive hormones and semen quality, with conflicting results.

In Pregnancy Study Online (PRESTO), a web-based prospective cohort study of North American couples, the researchers surveyed 4,194 women aged 21 to 45 living in the United States or Canada. The study specifically targeted women in stable relationships who were not using contraception or fertility treatment.

 Female participants were given the option to invite their male partners to participate; 1,125 of their male partners enrolled. The researchers found that during the period from 2013 through 2017, approximately 12 percent of female participants and 14 percent of male participants reported marijuana use in the two months before completing the baseline survey.

 After 12 cycles of follow-up, conception probabilities were similar among couples that used marijuana and those that did not. The researchers stressed that questions about the effects of marijuana use remain. Classifying people correctly according to the amount of marijuana used, especially when relying on self-reported data is challenging.
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HPV vaccine does not cause infertility

The human papilloma virus HPV is  a family of viruses, there are over 110 different types of HPV and more than 50 types that affect the genitals.
Different types of HPV are either high risk or low risk, depending on the conditions they can cause.

Some types of HPV can cause warts or verrucas. Others are associated with cervical cancer. Infection with low-risk HPV causes no symptoms and goes away without treatment. But infection with some high-risk types of HPV can cause abnormal tissue growth and cell changes that can lead to cervical cancer.

HPV infection is spread during sexual intercourse, it has been linked with reduced semen quality and lower pregnancy rates. Sexually transmitted infections STIs are associated with lower fertility, but vaccinated women with an STI history had about the same chance of becoming pregnant as unvaccinated women who had never had an STI.

Infection with other types of HPV may cause genital warts, skin warts, verrucas, vaginal cancer or vulval cancer. There is no adverse effects of HPV vaccination on fertility.

HPV is common, almost all sexually active men and women get the virus at some point in life. Having HPV can increase the risk of cervical cancer and removing cancerous or precancerous cells from cervix can reduce fertility.
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Epigenetic modifications of sperm DNA

Phthalates are compounds found in plastics and personal care products. Exposure to phthalates disrupts some hormones and it is associated with changes in male reproductive measures of semen quality and androgen levels.
 DNA methylation, one mechanism of epigenetics, is a chemical tag on DNA that does not change the gene sequence but is involved in controlling gene expression.

Father's environmental health contributes to reproductive success. For sperm to mature in three months, it shows that the preconception time-period may represent an important developmental window by which environmental exposures may influence sperm epigenetics early life development.

The researchers examined men's urine samples at the IVF clinic the same day they donated sperm, measured 17 metabolites from 8 different phthalate parent compounds in that sample, then performed DNA methylation analyses on sperm cells to examine statistical associations.

DNA was extracted and analyzed on a genomics system that examines many sites for DNA methylation on sperm used for IVF. Researchers identified many regions of interest in assessing a correlation between phthalate metabolite exposure and DNA methylation.

 Some of the region examined were associated with at least one of the phthalate metabolites, most of the phthalates that were associated with sperm DNA methylation were known or suspected to be anti-androgenic compounds, which means they can influence hormones. After examining the biological pathways, or common links between genes, that might be affected in these regions that were identified.

 Researchers discovered that many of the regions were related to genes involved in growth and development and cellular function and maintenance.
Some of the sperm DNA methylation regions were associated with poor blastocyst stage of embryo quality as defined by the IVF clinic's standards related to embryo quality before transfer into the uterus of the female partner to establish a pregnancy.

Sperm carry some of environmental legacy to the next generation. What the sperm cell encounters during development can influence these DNA methylation and it may have an effect on the developing embryo and offspring.
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