In humans, other mammals, and birds, the heart is divided into four chambers: upper left and right atria; and lower left and right ventricles. Commonly the right atrium and ventricle are referred together as the right heart and their left counterparts as the left heart.
Best Answer: Well they always calculate due date based on your period. Even the doctor will. If you know your exact date of conception you either add 2 weeks to that date or just count 38 weeks from that date.40 weeks gestation is based on your last period. So technically speaking a women is never actually pregnant for her first 2 weeks.est Answer: Well they always calculate due date based on your period. Even the doctor will. If you know your exact date of conception you either add 2 weeks to that date or just count 38 weeks from that date.
If your cycle is usually longer than 28 days, you're more likely to deliver later; and if it's shorter, earlier. But the most accurate way to date a pregnancy is via ultrasound measurement of the fetus's crown-to-rump length between eight and 12 weeks. Extreme fatigue is very common in the first trimester of pregnancy.