As fertilization occurs 14 days prior to the expected missed period and in previously normal cycle of 28 days duration, it is about 14 days after the first day of the period. Thus the true gestation period is to be calculated by substracting 14 days from 280 days i.e. 266 days. This is called fertilization or ovulatory age. It appears following the missed period till the end of first trimester. It can be in form of nausea on rising from the bed or vomiting and loss of appetite.
Easy fatigability is a frequent symptom.
There is enlargement of breast and delicate veins visible under the skin. Nipple and areola became more pigmented especially in dark women. Thick yellowish secretion can be expressed from nipple as early as 12th week. Pelvic changes - Uterus remains a pelvic organ till 12th week. These changes may help in the diagnosis of pregnancy.