What to Expect: Your First Trimester

The first trimester contains the most suspense and mystery for new moms. Many women who are trying to have a baby are impatient to find out as soon as they’re pregnant. However, the earliest an at-home pregnancy test can detect your pregnancy is week three. Only the most sensitive tests can detect pregnancy this early, and most won’t work until the end of week four (which coincides with your missed period). These tests look for elevated levels of the pregnancy hormone hCG, which takes some time for your body to produce once your baby begins to grow. Some women don’t see a positive result from a pregnancy test until week five or six. Because the first trimester is defined as weeks 1 through 12 of your pregnancy, this delay means you may not know you’re pregnant until halfway through the first trimester!
Common Symptoms
You may start to experience symptoms even before your pregnancy is confirmed by a urine or blood test. Nausea is the most common symptom by far, experienced by more than 85% of women. For many women, “morning sickness” is a misnomer; it’s common to experience nausea throughout the day. Morning sickness is usually related to hormones and can be alleviated by eating crackers or toast before getting out of bed in the morning. However, pregnancy-related nausea can be triggered by stress, hormones, and (oddly enough) hunger. 
Some light bleeding is not out of the ordinary during the first trimester. Light spotting can even be a sign that the fertilized egg has implanted in your uterus. Heavy bleeding or discolored vaginal discharge should be discussed with your doctor. 
Though your baby’s arrival is still nearly nine months away, your milk ducts will begin preparing to feed your newborn at the beginning of your pregnancy. This means you may feel breast tenderness as early as your first trimester. Your changing breasts will grow larger, requiring a new bra for support. Keep in mind that you’ll probably have to shop for bras several times throughout your pregnancy as your body changes. 
Constipation, gas, and bloating are frequent results of hormonal changes and will likely arise during the first trimester. These symptoms can be exacerbated by prenatal vitamins (but they’re good for you and your baby, so take your vitamins!). Eat fiber, drink fluids, and exercise to keep your insides moving smoothly. 
Many women find themselves worn out by the added energy load of pregnancy. During your first trimester, your baby is growing astonishingly fast. From a tiny bundle of cells almost too small to see with the naked eye, he or she will be the size of a plum. Your body is fueling all that growth, so expect to be tired. You may find yourself needing to nap during the day, or cope by going to bed earlier than usual. 
Visiting the Doctor
Despite how rapidly your baby is growing, you won’t see evidence of that growth until your bump starts to show in your second trimester. During the first trimester, you can only see your baby and hear his or her heartbeat at an ultrasound appointment. 
Typically, your first OB-GYN visit will be around week eight. Your physician will perform a host of tests. One of these tests will medically confirm your pregnancy. Others will check your general health and screen specific factors that can affect your health and your baby’s health during pregnancy. Your physician will likely perform an ultrasound, and you’ll get to hear your baby’s heartbeat for the first time. At this visit, you’ll also receive a predicted due date based on your missed period and the baby’s current measurements. Your physician will revise this estimate throughout the pregnancy as your baby grows.