reproductive health

A Spanish study rules out men’s lifestyle habits as an explanation for geographical differences in semen quality. The findings, presented at the annual congress of the European Society of Human Reproduction and Embryology (ESHRE), the abstract of which is to be published today in the journal Human Reproduction, are based on data from 386 men who attended seven assisted reproduction centres across the country between June 2024 and December 2025. They answered questions about their lifestyle habits (physical activity, tobacco use, alcohol consumption, coffee intake, etc.), their place of residence and their body mass index, amongst other factors. Semen quality was higher among men from northern Spain, even though lifestyle habits were similar across all regions, suggesting that differences in quality may be due to exposure to environmental pollutants, says the lead author.

A systematic review with a meta-analysis published in The Lancet Obstetrics, Gynecology, & Women’s Health concludes that there is insufficient evidence that most complementary treatments for in vitro fertilization (IVF) improve fertility in patients undergoing this procedure. Some of these techniques involve introducing platelet-rich plasma into the uterus or ovaries, administering a lipid infusion into the bloodstream, administering corticosteroids, or performing preimplantation genetic testing to detect aneuploidies—that is, abnormalities in chromosome number. According to the study, which included 85 clinical trials, there is only evidence—albeit of low quality—suggesting a possible benefit from three treatments: EmbryoGlue—a method of embryo transfer containing hyaluronic acid—endometrial scraping, and physiological intracytoplasmic sperm injection—a technique for selecting sperm.

A team in China has studied the ability of a test to detect the human papillomavirus (HPV)—responsible for the vast majority of cervical cancers—in menstrual blood from more than 3,000 women. The results indicate that the test is comparable to current screening performed in medical offices. According to the researchers, “Using menstrual blood for HPV testing is practical and non-invasive, allowing women to collect samples at home and thus potentially offering a practical way to expand access to screening.” The study is published in The BMJ. 

Around 15% of recognized pregnancies end in miscarriage, and it is estimated that almost half of all conceptions are lost in early stages, without people even realizing it. Now, a team from the United States and Denmark has analyzed data from more than 139,000 embryos from in vitro fertilization of nearly 23,000 couples and has found several genetic variants associated with a higher risk of miscarriage. Many of these are associated with meiosis, a key cell division process in sex cells. The authors, whose study is published in Nature, acknowledge that the new data will not allow for a precise estimation of individual risk, because the most important factors remain age and environmental elements.

The use of hormonal contraceptives is associated with a small increase in the risk of breast cancer—one additional case of cancer for every 7,752 women who use these drugs—according to a Swedish study. The risk varies depending on the type of hormones administered, and is slightly higher with the use of contraceptives containing desogestrel. The study, published in JAMA Oncology, analyses data from a national registry between 2006 and 2019, with more than two million women aged between 13 and 49.

The decline in egg quality has been considered the main cause of declining fertility with age. A new study published in Science shows that the cells and tissues surrounding the oocytes within the human ovary also play a crucial role. They identified 11 types of cells in the ovaries, including nervous system cells, that influence follicle development. In addition, they have discovered that oocytes are grouped into “pockets” within the ovary and that the density within these pockets declines over the years. 

An international team has succeeded in generating fertilisable human eggs from skin cells using a novel technique. According to the authors, the study offers a way to address infertility, although they acknowledge that further research is needed to ensure efficacy and safety before future clinical applications. Of the 82 functional oocytes generated and fertilised, only 9% developed to day 6, when the experiment ended. In addition, the embryos had chromosomal abnormalities. The results are published in the journal Nature Communications.

Menstrual cycles were synchronised with lunar cycles until 2010, but according to research published in Science Advances, after this date, this synchrony is only found in January, when lunar gravity is at its strongest. The team analysed the menstrual records of 176 women and attributes the loss of synchrony to the increasing use of smartphones and LED night lights, which became widespread from 2010 onwards.

A Canadian team analysed samples from women undergoing in vitro fertilisation and found that higher concentrations of THC metabolites—the main psychoactive substance in cannabis—were associated with a higher rate of oocyte maturation and a lower number of embryos with the correct number of chromosomes. The latter could be replicated at similar concentrations under laboratory conditions. The authors, who published their findings in the journal Nature Communications, acknowledge that the study does not have sufficient statistical power to draw conclusions, but it does warn of possible risks to women's fertility.