The first trimester spans weeks 1-13 of pregnancy, a critical period when all major organs and body systems form. Your baby develops from a fertilized egg to a fetus with recognizable human features, growing from microscopic size to about 3 inches long. You'll experience significant hormonal changes causing various symptoms. This trimester carries the highest miscarriage risk, which decreases significantly after 12 weeks. Your first prenatal appointment typically occurs around 8-10 weeks.

Extreme fatigue in the first trimester results from rapidly rising progesterone levels, which have a sedative effect. Your body is working hard creating the placenta, increasing blood volume by 50%, and supporting rapid fetal development. Lower blood sugar and blood pressure contribute to tiredness. This exhaustion usually improves in the second trimester. Rest when possible, maintain good nutrition, stay hydrated, and engage in light exercise if energy permits.

First-time mothers typically begin showing between 12-16 weeks, though this varies greatly. You might notice your clothes fitting tighter around week 8-10 due to bloating before actual baby bump appears. Second and subsequent pregnancies often show earlier because abdominal muscles have been stretched before. Body type, weight, and whether you're carrying multiples affect when you show. Some women don't show noticeably until the second trimester.

Many medications are unsafe during the critical first trimester when organs form. Always consult your healthcare provider before taking any medications, including over-the-counter drugs and supplements. Acetaminophen is generally considered safe for pain and fever. Avoid NSAIDs like ibuprofen and aspirin. Don't stop prescribed medications without provider approval, as some conditions require continued treatment. Your provider will weigh medication risks against benefits for your specific situation.