Everything you need to know about the first trimester (weeks 1 to 12)
You’re pregnant: congratulations! The first weeks of your pregnancy are a vital time as your body gets busy building a baby. How exciting!
First trimester: key stages
The first trimester begins on the first day of your last period and lasts until the end of week 12. This means that by the time you know for sure you’re pregnant, you might already be five or six weeks pregnant!
A lot happens during these first three months. The fertilised egg rapidly divides into layers of cells and implants in the wall of your womb where it carries on growing. These layers of cells become an embryo, which is what the baby is called at this stage.
During this trimester, your baby grows faster than at any other time. By six weeks, a heartbeat can usually be heard and by the end of week 12, your baby’s bones, muscles and all the organs of the body have formed. At this point, your baby looks like a tiny human being and is now called a fetus. He or she will even be practising swallowing!
The first trimester of pregnancy is marked by an invisible — yet amazing — transformation. And it happens quickly. Knowing what physical and emotional changes to expect during the first trimester can help you face the months ahead with confidence.
While your first sign of pregnancy might have been a missed period, you can expect several other physical changes in the coming weeks, including:
- Tender, swollen breasts. Soon after conception, hormonal changes might make your breasts sensitive or sore. The discomfort will likely decrease after a few weeks as your body adjusts to hormonal changes.
- Nausea with or without vomiting. Morning sickness, which can strike at any time of the day or night, often begins one month after you become pregnant. This might be due to rising hormone levels. To help relieve nausea, avoid having an empty stomach. Eat slowly and in small amounts every one to two hours. Choose foods that are low in fat. Avoid foods or smells that make your nausea worse. Drink plenty of fluids. Foods containing ginger might help. Contact your health care provider if your nausea and vomiting is severe.
- Increased urination. You might find yourself urinating more often than usual. The amount of blood in your body increases during pregnancy, causing your kidneys to process extra fluid that ends up in your bladder.
- Fatigue. During early pregnancy, levels of the hormone progesterone soar — which can put you to sleep. Rest as much as you can. A healthy diet and exercise might increase your energy.
- Food cravings and aversions. When you’re pregnant, you might become more sensitive to certain odors and your sense of taste might change. Like most other symptoms of pregnancy, food preferences can be chalked up to hormonal changes.
- Heartburn. Pregnancy hormones relaxing the valve between your stomach and esophagus can allow stomach acid to leak into your esophagus, causing heartburn. To prevent heartburn, eat small, frequent meals and avoid fried foods, citrus fruits, chocolate, and spicy or fried foods.
- Constipation. High levels of the hormone progesterone can slow the movement of food through your digestive system, causing constipation. Iron supplements can add to the problem. To prevent or relieve constipation, include plenty of fiber in your diet and drink lots of fluids, especially water and prune or other fruit juices. Regular physical activity also helps.
Pregnancy might leave you feeling delighted, anxious, exhilarated and exhausted — sometimes all at once. Even if you’re thrilled about being pregnant, a new baby adds emotional stress to your life.
It’s natural to worry about your baby’s health, your adjustment to parenthood and the financial demands of raising a child. If you’re working, you might worry about how to balance the demands of family and career. You might also experience mood swings. What you’re feeling is normal. Take care of yourself, and look to loved ones for understanding and encouragement. If your mood changes become severe or intense, consult your health care provider.