The first month of pregnancy, known as the first trimester, typically covers the period from the first to the fourth week after conception. However, healthcare providers often use a different calculation called weeks of amenorrhea (SA), which starts from the date of a woman's last menstrual period. This is usually about two weeks before conception, and it's easier to track than the exact date of fertilization. The first month of pregnancy, therefore, is counted from 3 SA to 6 SA, which covers the first four weeks of development after conception. At this early stage, many women may not yet notice any symptoms and might not realize they are pregnant. The first sign is often the absence of a menstrual period on the expected date. As the first month progresses, some women may experience symptoms such as tender or swollen breasts, nausea with or without vomiting, frequent urination, and mood changes. Light bleeding can also occur due to the implantation of the embryo in the uterus, but if the bleeding is accompanied by lower abdominal pain or on one side, it could indicate a miscarriage or ectopic pregnancy, which requires immediate medical attention. A pregnancy test can be taken as soon as symptoms appear to confirm pregnancy. Urine tests available at pharmacies are reliable and detect the hormone beta HCG, which appears in urine about 10 days after fertilization. A blood test can also provide a numerical result. It is recommended to see a general practitioner, gynecologist, or midwife to confirm the pregnancy, perform a clinical exam, and provide an estimated due date. If available, an ultrasound may be done to check the embryo's location in the uterus. Blood tests may be prescribed to determine the blood group and screen for infectious diseases like toxoplasmosis and rubella, along with a urine test to check for albumin. During the first month of pregnancy, it is important to adopt a healthy lifestyle. This includes eating a balanced diet rich in fruits, vegetables, and foods containing folic acid. It is advisable to limit fatty foods and caffeine, avoid raw or smoked fish and meats, and eat only well-cooked meats. Dairy products made from raw milk should be avoided, and fruits and vegetables should be thoroughly washed if eaten raw. Alcohol should be completely avoided, and help to quit smoking should be sought if needed. Strenuous sports should be stopped, and any medications should be discussed with a healthcare professional. By the end of the first month, the fertilized egg has developed into a zygote and implants in the uterus as early as the 7th day. By the fourth week, the embryo is about 4 mm in size and has begun to form the early stages of a nervous system, limb buds, and the outlines of several organs, along with the beginning of a circulatory system. Four distinct areas can be identified: right side, left side, back, and stomach. The primitive heart starts to beat at 4 weeks, but it is only detectable via ultrasound in the 5th week.