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sex before periods will not have any effect on periods because the periods are caused due to a natural cycle which goes on in a woman's body which is controlled by various hormones from the hypothalamus(higher center in the brain). when the levels of certain hormones drop the period commenses. stress
ofcourse does have an effect on the timing of the periods. if you have missed your period then you should wait for 7 days and get a blood test
, serum beta hcg
titre if you do not get your period. sometimes the periods can be delayed, but if beyond 7 days you should rule out pregnancy
. if not pregnant then other causes can subsquently be evaluated.