Protection of the schoolgirls' reproductive health that often depends on many factors, one way or another associated with low awareness of the issue, is a global priority in modern society. The study was aimed to assess the factors that affect reproductive health of the school-age girls. An online questionnaire survey of 100 girls aged 15–18 aimed at detecting reproductive health problems was carried out in Moscow. The average age of menarche was 12.3 ± 1.2 years, however, there were girls, who had menarche at the age of 10 years (10%), and those, who had menarche after the age of 14 (7%), among schoolgirls. Blood spotting between periods was observed in 21% and pelvic pain in 44% of schoolgirls; 81% had severe pain. Irritability, aggression, easy crying, rapid fatigue, and faintness before and during the periods were reported by 98%; swelling, weight gain, abdominal distension, constipation, diarrhea, breast engorgement and soreness were reported by 73%; headache, vertigo, nausea, vomiting, insomnia, increased sensitivity to smell and sound were noted by 50%; high blood pressure, heart-related pain, increased heart rate, panic attacks were reported by 21%; menstrual disorders were observed in 16% of school-age girls. The study showed that 60% of schoolgirls demonstrated medium awareness, 28% showed high awareness, and 12% had insufficient knowledge about reproductive health. The schoolgirls' insufficient awareness of the reproductive health-related issues is a major medical and social challenge that can negatively affect the schoolgirls' reproductive health and cause not only various reproductive system disorders, but also reproductive losses and even infertility later in life.