Understanding Your Pregnancy Timeline
A standard pregnancy lasts about 280 days safely (40 weeks). Medically, the clock starts ticking on the first day of your last normal menstrual period (LMP)—which means for the first two weeks of your "pregnancy," you technically aren't pregnant yet. You only conceive around week 2 or 3!
The Three Trimesters
- First Trimester (Weeks 1-12): This is the most crucial stage of fetal development. The body structure and all major organ systems begin to form. For the mother, this is typically when morning sickness, fatigue, and breast tenderness are most prominent.
- Second Trimester (Weeks 13-27): Often called the "honeymoon phase" of pregnancy. Nausea usually subsides, energy levels return, and the baby bump becomes noticeable. You will likely feel the baby move for the first time (quickening) between weeks 16-20.
- Third Trimester (Weeks 28-40+): The final stretch. The baby gains significant weight and prepares for birth. Physical symptoms for the mother return in the form of backaches, frequent urination, and shortness of breath as the baby takes up more space.
Why Choose Ultrasound Dating?
If you have irregular periods, recently stopped taking birth control, or are unsure of your exact LMP, your healthcare provider will schedule an early ultrasound. During the first trimester, embryos grow at a very predictable rate, so measuring the Crown-Rump Length (CRL) gives an incredibly precise gestational age and due date. Once established by an early ultrasound, your official due date rarely changes.