Update knowledge.txt

knowledge.txt

@@ -0,0 +1,18 @@
+A period is a release of blood from a girl's uterus, out through her vagina. 
+It is a sign that she is getting close to the end of puberty. 
+It also means that she can get pregnant if she has sex.
+There is a lot to learn about periods. Here are answers to some common questions.
+When Do Periods Usually Start?
+Most girls get their first period when they're around 12. 
+But sometimes it comes a few years earlier or later. 
+Every girl's body has its own schedule.
+There isn't one right age for a girl to get her period. 
+But signs to watch for include:
+breasts starting to develop (periods usually start about 2 years after this), hair growing under a girl's arms and in her private parts, seeing or feeling vaginal discharge fluid (sort of like mucus), which usually begins about 6 months to a year before a girl gets her first period
+What Causes a Period?
+A period happens because of changes in hormones in the body. 
+Hormones are chemical messengers. 
+The ovaries release the female hormones estrogen and progesterone , which cause the lining of the uterus (or womb) to build up. 
+The built-up lining is ready for a fertilized egg (an egg that has joined with a sperm) to attach to and develop into a baby. 
+If there is no fertilized egg, the lining breaks down and bleeds. 
+Then the same process happens all over again.