June 15, 2022 Author : Cláudia Gerra The menstrual cycle is a set of physiological (normal) events that recur in women during childbearing age giving rise to ovulation and a possible pregnancy. Menstruation (menses or menstrual period) is one of the events of the menstrual cycle . The first day of menses is the first day of a menstrual cycle; A menstrual cycle ends the day before a new menstruation; In a healthy adult woman, a menstrual cycle lasts on average 28-35 days; A menstrual period lasts on average 3-7 days; If a pregnancy occurs, the menstrual cycle and menstruation are interrupted. Duration and phases of the menstrual cycle Not even in the same woman, menstrual cycles are always the same throughout the childbearing. In general: The first cycles after the first menstruation (or menarche) are further away from the average duration and are more irregular between them; Between the ages of 20 and 40, the cycles are more regular; As menopause approaches, menstrual cycles become more irregular again, until they stop when menopause is reached. The menstrual cycle has two main phases , which are separated by ovulation: The follicular phase It starts on the first day of the menstrual cycle; It ends before the peak of luteinizing hormone (LH) that causes ovulation; This phase is primarily responsible for the variation in the duration of the menstrual cycle; On average it takes 14-21 days. The luteal phase It starts on the day of peak luteinizing hormone (LH) and ovulation; It ends on the last day of the menstrual cycle; Lasts an average of 14 days. In a 28-day menstrual cycle, each of the two phases lasts 14 days. Changes throughout the menstrual cycle Throughout the menstrual cycle, there are mainly changes in the ovaries and endometrium (inner layer of the uterus wall) and in the levels of some hormones . The main hormones that regulate the menstrual cycle are: Follicle stimulating hormone (FSH) , which is produced by the pituitary; Luteinizing hormone (LH) , which is produced by the pituitary; Estrogens (mainly estradiol), which are produced by the follicles in the ovaries; Progesterone , which is produced by the corpus luteum that forms at the site of an ovulating follicle. FSH and LH stimulate the development of ovarian follicles , promote ovulation, and stimulate the production of estrogen and progesterone by the ovaries. Estrogens and progestins contribute to the preparation of the uterus for possible fertilization. In the follicular phase, a set of ovarian follicles begins to develop, one of which will ovulate. After ovulation, the corpus luteum forms at the site of the ovary from which this follicle is released. If the egg is fertilized and the embryo implanted in the uterus, the corpus luteum remains during pregnancy. I f there is no fertilization or implantation , the cycle continues with the luteal phase, the corpus luteum will disappear, the concentrations of ovarian hormones decrease and a new cycle begins with menstruation. Ovulation The days around ovulation are the fertile days . Pregnancy is more likely to occur if you have sex within three days before ovulation and up to 24 hours after ovulation. Menstruation Menstruation elimination through the vagina of endometrial (the innermost layer of the uterus wall) tissue accompanied by bleeding . It lasts an average of 5 days (3-7 days). The first menstruation is called menarche and represents the beginning of a woman childbearing age. It occurs on average between 10 and 14 years of age and is one of the events of female puberty. Before menarche: Begins breast growth; The first pubic hairs appear; An important phase of increasing stature takes place. Underarm hair and changes in body shape (increased body fat that accumulates in the hips and thighs) usually occur after the first menstrual period. The interval between breast development and the first menstruations is usually about 2-3 years. The first menstruations can be irregular in duration , taking up to 5 years to become regular. Meet the obstetrics-gynecology clinical team from Hospital da Luz network and book your consultation The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
