The first trimester includes the period from week 1 to week 12 – about the first three months of pregnancy. It’s the period of early fetal development, which starts when the egg is fertilized by a sperm cell.
Although you probably won’t be visibly pregnant, the first trimester is a time of incredible transformation. Knowing what changes to expect can prepare you for the months ahead with a positive, healthy attitude.
What To Expect
week by week
Breast sensitivity. With hormonal changes caused by pregnancy come changes to the body. And nowhere are those changes more noticeable than in the breasts. During the first trimester, your breasts may be unusually sensitive, and will likely grow significantly in size, too.
Nausea and fatigue. The nausea and fatigue that start at the beginning of pregnancy often continue throughout most of the first trimester. You can minimize fatigue by resting as often as possible, eating a diet rich in protein and iron, and including exercise in your daily routine. Also, fight off nausea by eating small, frequent meals that are low in fat. If a certain food smells bad to you, avoid it. If your nausea persists, ask your doctor about treatment possibilities.
Constipation. Some women may experience constipation as their uterus grows in size, putting pressure on the intestines and rectum. If you’re experiencing constipation during the first trimester, eat lots of fresh fruit and other foods high in fiber, and drink plenty of water.
Dizziness. Due to perfectly normal changes in your circulation, you may feel dizzy during your first trimester. If you experience dizziness, avoid long or prolonged standing, and don’t stand too quickly after sitting or lying down. If you experience extreme dizziness – or if it occurs in conjunction with abdominal pain or bleeding – consult your doctor immediately. Such symptoms may indicate an ectopic pregnancy (where the fertilized egg is implanted outside the uterus), which requires the removal of the ectopic tissue.
Emotional changes. For many women, pregnancy is a roller coaster ride. One minute, they’re ecstatic. The next, exhausted. And let’s be honest – although pregnancy is an exciting time, it’s also stressful. After all, it’s natural to worry about everything from your baby’s health to the new responsibility of becoming a parent. Don’t worry if you feel a little crazy at times – that’s totally normal. Just eat well, get plenty of rest, and depend on those close to you for support and understanding. If things get too tough, don’t hesitate to consult your doctor for additional support.
Your Baby's Development
The first trimester is a time of exciting – if not always very visibly noticeable – growth and movement for your baby. During this time, your body is undergoing an incredible amount of change. And for some women, it includes some unpleasant side effects. Not to worry, though, as most of these disappear almost entirely by the second trimester.
Weeks 1 and 2: Believe it or not, you aren’t technically pregnant during the first week or two of the time the doctor allots for your pregnancy. This is because your doctor typically counts ahead 40 weeks from your last period – and conception usually takes place about two weeks after your period begins.
Week 3: Now that the sperm and egg have united to form a zygote, you’re officially pregnant. But your new baby is only a microscopic ball of cells at this point. Even so, he or she is growing at a remarkable rate.
Week 4: Implantation occurs during week 4. This is when the zygote reaches your uterus and burrows into its wall for nourishment. The placenta also begins to form at this time.
Week 5: Now your baby is evolving into an embryo, which means its basic organs – the spinal cord, heart, and others – are beginning to form. Early skeletal development is also possible during week 5.
Week 6: By now, your baby is beginning to resemble a little human being more and more. Dark spots are forming where its eyes will be, and pits are appearing on either side of the head, where the ears will develop.
Week 7: Your baby’s brain and face are now developing at a rapid rate. Tiny nostrils are now visible, and the eye lenses are forming. Those paddles on each side of its torso? Those are arms!
Week 8: Your baby’s fingers are beginning to form, and its limbs are growing longer. The eyes and nipples are also visible, and the trunk of the baby’s body is starting to straighten. Although the baby may begin to move this week, you won’t be able to feel it yet.
Week 9: In week 9, your baby develops bones in its arms – which, by the way, it can now bend at the elbows. Also, the eyes and ears continue to develop.
Week 10: Your baby’s neck is now beginning to form, and his or her eyelids can now close to protect the eyes as they develop.
Week 11: The body continues to grow rapidly, and the baby is now officially a fetus. Red blood cells are forming in the baby’s liver. By the end of the week, the sexual organs will begin developing.
Week 12: The fingernails are developing, and the face has a visibly human profile. At this point, the baby may be as long as 2.5 inches and weigh up to 0.5 ounces.
Tests and Screenings
As soon as you suspect pregnancy, you should schedule your initial prenatal appointment. If possible, have your partner join you. Be prepared to spend a good deal of time at the doctor’s office – the initial visit typically lasts upwards of two hours.
Initial prenatal visit. During this visit, expect the doctor to check your weight, height, and blood pressure, listen to your heart, and assess your overall health. The doctor may also perform a vaginal exam, and check the cervix for any abnormalities or infections. If you haven’t had one recently, you may require a Pap smear. The doctor may also conduct an early ultrasound to confirm the pregnancy and the baby’s due date.
Lab tests. Your doctor may test to determine your blood type and Rh factor – a protein in your red blood cells. Blood tests are also used to screen for any potential health concerns such as the presence of STDs or other diseases. A bladder analysis may also be performed to screen for bladder or kidney infections. An excess of sugar or protein in your urine could indicate diabetes or a kidney condition.
Screenings. Various prenatal tests can be performed to provide important information about the health of your baby. The doctor may offer to conduct an ultrasound, blood tests or other types of screenings intended to detect potential fetal abnormalities.
Health and Nutrition
Exercise tips. In general, during your first trimester, you are safe to continue exercising as you were prior to becoming pregnant. But it’s important to avoid any activities that put you at an increased risk for injury. Horseback riding and contact sports, for example, should be avoided. In general, avoid activities that might lead to collisions, blunt contact with a racquet or a ball, or anything that requires abrupt side-to-side movements.
Healthy eating. Your baby needs a variety of nutrients, so it’s important that you eat a variety of foods. Fresh fruit and veggies, whole grains, and lean meats are particularly important during your first trimester. Also, most breads and cereals are high in folic acid, which helps protect babies against neural tube defects. If you aren’t sure what you should be eating, talk to your doctor. He or she will be able to help you arrive at a diet that will help you and your baby stay healthy without gaining more weight than necessary.
Foods to avoid. Although most foods are safe during pregnancy, there are some that can be hazardous to your baby.
- Abstinence from alcohol is recommended.
- Uncooked seafood, such as sushi, and rare or undercooked beef or poultry should be avoided.
- Deli meats (including smoked seafood) have been known to be contaminated with listeria, which can cause miscarriage. If you eat deli meats, heat them until they steam before eating.
- Fish with high mercury levels – such as shark, swordfish, and king mackerel – should be avoided. Canned tuna – and most fish in general – should be eaten in moderation only.
- Raw or undercooked shellfish – oysters, clams, and mussels – should be avoided entirely.
- Raw eggs, or foods containing them, should be avoided due to potential exposure to salmonella.
- All soft cheeses should be avoided, unless pasteurized. Likewise, do not drink unpasteurized milk.
- Avoid drinking caffeine during the first trimester, as some studies have shown a correlation between caffeine intake and miscarriages.
- Definitely eat vegetables, but be sure to wash them thoroughly prior to eating them to avoid the risk of exposure to toxoplasmosis, which may contaminate the soil where some vegetables are grown.
Prenatal vitamins. Eating right is crucial to getting the vitamins and minerals you and your baby need. But you should still supplement your diet with prenatal vitamins. Why?
Pregnant women need extra amounts of certain nutrients to ensure both their own and their baby’s health. For example, folic acid helps prevent neural tube defects. Calcium promotes strong bones and teeth – in both mother and baby. Iron aids in the development of blood and muscle cells in mother and baby.
Most prenatal vitamins contain levels of folic acid, calcium, and iron not found in regular multi-vitamins. By taking prenatal vitamins, you can make doubly sure you’re getting enough of these important nutrients during your pregnancy. While some prenatal vitamins are available over-the-counter, others require a prescription. Ask your doctor what types of prenatal vitamins might be right for you.