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If you have not had Intercourse and if she has not had come in contact with your semen, then don't worry as there will be no chances of Pregnancy
. She could have missed her periods due to stress
Imbalance. Since she has missed her Periods, wait for a week. Then get a Urine Pregnancy Test done using a early morning urine sample to confirm it. If it is negative, Kindly get her examined by a Gynecologist so that she can examine her and rule out the cause for missed periods. She will require Hormonal drugs. Ask her to eat healthy balanced diet which should include fresh fruits and Green leafy veggies and avoid stress. Let her exercise regularly.