The vast majority of pregnancies do not occur until about 1 month after intercourse. On the day of intercourse, if the sperm and egg have united, it will take about half a month for them to enter the uterine cavity and become established, then they will grow and develop and secrete blood HCG. Vomiting. Due to individual differences, the symptoms of nausea and vomiting may vary from mild to severe, and some may even require hospitalization for rehydration and correction of electrolyte disturbances. Early pregnancy reactions also include local changes in the breasts, which may become enlarged and softer under the effect of estrogen, and the nipples and areolas may become colored.