If you're carrying twins or other multiples, you might have even more questions about your pregnancy week by week. How much weight should you gain? How can you prevent preterm labor? Will you need bed rest?

Whatever your questions, understanding your pregnancy week by week can help you make good decisions throughout your pregnancy. Learn nutrition do's and don'ts, and get the basics on other healthy pregnancy issues — from exercise to back pain and sex. The more you know about your pregnancy week by week, the more prepared you'll be to face what lies ahead.

The first trimester of pregnancy can be overwhelming. Understand the changes you might experience and how to take care of yourself during this exciting time.

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.

Whether you choose a family doctor, obstetrician, nurse-midwife or other pregnancy specialist, your health care provider will treat, educate and reassure you throughout your pregnancy.

Your first visit will focus on assessing your overall health, identifying any risk factors and determining your baby's gestational age. Your health care provider will ask detailed questions about your health history. Be honest. If you're uncomfortable discussing your health history in front of your partner, schedule a private consultation. Also expect to learn about first trimester screening for chromosomal abnormalities.

After the first visit, you'll probably be asked to schedule checkups every four weeks for the first 32 weeks of pregnancy. However, you may require more or less frequent appointments, depending on your health and medical history. During these appointments, discuss any concerns or fears you might have about pregnancy, childbirth or life with a newborn. Remember, no question is silly or unimportant — and the answers can help you take care of yourself and your baby.

You can find out if and when the best time to start taking pregnancy vitamins is in this article.