What is infertility?
Infertility refers to the inability of a couple to conceive a child after at least one year of regular, unprotected sexual intercourse. It can also refer to the inability to carry a pregnancy to term. Infertility can affect both men and women, and it is a common reproductive health issue worldwide.
There are two types of infertility:
- Primary infertility: This occurs when a couple has never been able to conceive a child despite trying for at least one year.
- Secondary infertility: This occurs when a couple has previously conceived a child, but they are unable to conceive again after trying for at least one year.
Infertility can result from various factors, which may affect one or both partners:
- Female factors: Common causes of female infertility include ovulation disorders (e.g., polycystic ovary syndrome), fallopian tube blockage or damage, endometriosis, uterine fibroids, hormonal imbalances, and age-related decline in egg quality.
- Male factors: Male infertility can be due to problems with sperm production, sperm motility, or sperm function. Causes include low sperm count (oligospermia), poor sperm motility (asthenospermia), abnormal sperm morphology (teratospermia), hormonal imbalances, genetic factors, testicular injuries, infections, and lifestyle factors such as smoking, excessive alcohol consumption, and drug use.
- Combined factors: In many cases, infertility may be due to a combination of male and female factors or unexplained causes. Additionally, lifestyle factors such as obesity, poor nutrition, stress, and environmental factors (e.g., exposure to toxins or radiation) can also impact fertility in both men and women.
What is the relationship between infertility and oxidative stress?
The relationship between infertility and oxidative stress is complex and multifaceted, with oxidative stress implicated in various aspects of reproductive health in both men and women. Here’s how oxidative stress may contribute to infertility:
- Sperm Health: Oxidative stress can damage sperm cells by causing oxidative damage to their DNA, proteins, and cell membranes. This damage can impair sperm motility, viability, and morphology, leading to reduced sperm quality and fertility. Excessive production of reactive oxygen species (ROS) in the male reproductive tract, either due to endogenous factors (e.g., inflammation, infections) or exogenous factors (e.g., smoking, environmental toxins), can overwhelm the antioxidant defenses of sperm cells and contribute to male infertility.
- Ovulation Disorders: In women, oxidative stress can disrupt normal ovarian function and ovulation. Oxidative stress has been implicated in conditions such as polycystic ovary syndrome (PCOS), a common cause of female infertility characterized by hormonal imbalances, irregular menstrual cycles, and ovulatory dysfunction. Elevated levels of ROS in the ovaries can impair follicle development, ovulation, and oocyte quality, affecting fertility.
- Implantation Failure: Oxidative stress can compromise the endometrial environment and impair embryo implantation in the uterus. ROS can disrupt the delicate balance of hormones and cytokines necessary for successful implantation, leading to implantation failure and recurrent pregnancy loss. Chronic inflammation and oxidative stress in the uterine lining may also contribute to conditions such as endometriosis and uterine fibroids, which can negatively impact fertility.
- Aging and Reproductive Aging: Aging is associated with increased oxidative stress and declining fertility in both men and women. Oxidative damage accumulates over time in reproductive tissues, affecting gamete quality, hormonal regulation, and reproductive function. In women, advanced maternal age is associated with decreased ovarian reserve, reduced oocyte quality, and increased risk of chromosomal abnormalities in embryos. In men, aging is linked to declines in sperm quality, semen parameters, and reproductive capacity.
- Assisted Reproductive Technologies (ART): Oxidative stress can influence the success rates of assisted reproductive technologies (ART), such as in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). Exposure of gametes and embryos to oxidative stress during in vitro culture can compromise their viability and developmental competence, affecting the outcomes of ART procedures. Strategies to mitigate oxidative stress in ART settings, such as optimizing culture conditions, supplementation with antioxidants, and selection of healthy gametes, may improve IVF success rates.
Overall, oxidative stress is increasingly recognized as a contributing factor to male and female infertility, affecting various aspects of reproductive health and fertility.