Minimal. Common signs and symptoms of pregnancy usually start occurring by about 6 to 8 weeks and include breast tenderness, nausea (morning sickness), weight gain due to fluid retention, amenorrhea, urinary frequency, mild headaches, insomnia, fatigue, and constipation. Some of these will occur sooner than others during the pregnancy and some will progressively worsen during pregnancy.
Missed menses. A missed menstrual period is the best symptom known to man (and woman) since time began.
Late period. Late or missed period is the first, and the only completely reliable one.
The usual. Typical symptoms / signs are: missed period nausea or vomiting breast enlargement and tenderness urinary frequency fatigue.