Polycystic ovary syndrome (PCOS), an endocrine and metabolic disorder in women of reproductive age, is characterized by high androgen levels, irregular periods, and small cysts in the ovaries. PCOS affects approximately 10 % of reproductive age women of all races and ethnicities. PCOS has been recognized to affect women of reproductive age since antiquity and in the 21st century, it emerges as the most widespread and serious reproductive metabolic disorder in the world. PCOS is a multifactorial disorder that affects both the reproductive and metabolic health of women. In addition, PCOS is a leading symptom of infertility in women. Nevertheless, women with PCOS who become pregnant unfortunately have an increased risk of complications, such as gestational diabetes mellitus (GDM), preterm birth. Many people believe GDM disappears after childbirth, despite the fact that GDM is a war­ning symptom of type 2 diabetes mellitus, metabolic syndrome, and cardiovascular disease. According to growing evidence, GDM complicates 40 % of PCOS pregnancies, suggesting that PCOS is a risk factor for GDM. Hence, PCOS is a lifelong disorder that can eventually lead to various long-term health complications, including chronic menstrual irregularity, infertility, endometrial hyperplasia, and endometrial cancer. Thus, it’s a scientific fact that both PCOS and GDM are significantly associated with each other. However, most studies on the risk of GDM in PCOS patients are retrospective. Therefore, there is no strong evidence whether PCOS is a risk factor for GDM or any other related factor. PCOS, a polygenic endocrinopathy, is in a true sense a set of diseases that worsen the state of the body. Reproductive and metabolic disorders associated with PCOS cause several clinical symptoms, such as irregular and painful periods, hirsutism, acanthosis nigricans, acne, psoriasis, anxiety, mood swings, patterned baldness, cardiovascular problems, type 2 diabetes, infertility, pelvic pain, low libido, low self-esteem, etc. Further studies are needed to understand the genetic and epigenetic contributions of PCOS, PCOS-related comorbidities, the role of placenta in nutrient availability, and influence of medications that may affect the long-term offspring health.

Epigenetics studies the inherited changes in a phenotype or in expression of genes caused by other mechanisms, without changing the nucleotide sequence of DNA. The most distinguished epigenetic tools are: modifications of histones, enzymatic DNA methylation, and gene silencing mediated by small RNAs (miRNA, siRNA). The resulting m5C residues in DNA substantially affect the cooperation of proteins with DNA. It is organized by hormones and aging-related alterations, one of the mechanisms controlling sex and cellular differentiation. DNA methylation regulates all genetic functions: repair, recombination, DNA replication, as well as transcription. Distortions in DNA methylation and other epigenetic signals lead to diabetes, premature aging, mental dysfunctions, and cancer.