After puberty every women follows the monthly menstrual cycle but it get stop when you get pregnant or after certain age usually 45 years (menopause). The early most sign of pregnancy is amenorrhea (absence of menstruation). Why there is no menstruation during pregnancy? Why does menstruation cycle (period) stop during pregnancy? This article tries to explain the mechanism of amenorrhea during pregnancy.
The normal menstrual cycle will be of 28 days and it may vary with person to person ranging from 21 to 35 days. Those having menstruation cycle of 28 days will have ovulation (release of egg form ovary) at 14 days. After ovulation corpus lutem;(temporary endocrine gland ) that is formed in the ovary. It is the source of estrogen and mostly progesterone hormones.
If the egg does not fertilize with the sperm corpus lutem will degenerate and the supply of estrogen and progesterone will be decreased. Drop in the level of these hormones causes the shedding of uterine wall and menstrual bleeding occurs at 28 days of cycle and then new cycle begins.
If fertilization is successful then zygote will be formed. After few days of fertiliziation the covering of zygote ( syncytiotropoblast) begins to release the human chorionic gonadotropin hormone (hCG). In the presence of hCG hormone, corpus lutem will remain intact( healthy) and there is continues release of estrogen and progesterone hormones from corpus lutem.
The uterus wall bath with these hormones and prepare the uterine wall for the growing fetus (provide nutrients to fetus).
Therefore there is no shedding of uterine wall and there is no menstruation during pregnancy. The period stops after getting pregnant.
Estrogen and progesterone hormone are also secreted by placenta after its development. So, when there is stoppage of your period more than 40-45 days with history of unprotected sex, there is chance of pregnancy. You can check with pregnancy kit that shows the presence of HCG hormones in the urine. Presence of hCG hormone in blood and urine is indicative of pregnancy.