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First Trimester

Physical Changes and Symptoms of the First Trimester

  1. Fatigue
  2. Nausea and Vomiting (“Morning Sickness”)
  3. Urinary Frequency
  4. Breast Tenderness
  5. Headaches and Dizziness
  6. Weight Gain

Glimpses at the First Trimester



Pregnancy typically lasts 40 weeks, beginning from the first day of a woman’s last menstrual period which means that it includes the two weeks before ovulation and conception takes place. It is often referred to in three parts called trimesters. The first trimester lasts 12 weeks, the second from 13 to the end of 27 weeks, and the third from 28 to 40 weeks. These divisions are somewhat arbitrary and you may encounter slightly different versions of these time periods during your pregnancy. Your doctor will probably refer to your pregnancy by the age of the fetus in weeks.

Certain important milestones in pregnancy occur during each trimester. For example, specific tests are performed during the first trimester. The trimester divisions help both you and your doctor in the planning and management of your pregnancy.

The first trimester is a time of profound changes inside your body, and you’ll experience these changes in your own unique way. Some women know right away that they have conceived, whereas others may not be convinced that they’re pregnant even after a positive pregnancy test and confirmation by their physician. The first trimester may bring increased energy and a sense of well being. Some women may feel tired and emotional. Others may not notice changes until much later in pregnancy.

Physical Changes and Symptoms of the First Trimester

There are a number of physical changes during early pregnancy that may make you uncomfortable, but will not endanger your health or the health of your baby. Each pregnancy is unique, and you may experience many, some, or none of the changes and symptoms described here. It isn’t uncommon for a woman to have completely different experiences from one pregnancy to another. It doesn’t mean there is anything wrong with the pregnancy, but rather demonstrates the variation in pregnancies. Knowing what the symptoms mean, in terms of what is happening inside your body, and knowing what you can do to make yourself more comfortable will help you cope with the adjustments in early pregnancy. If this is not your first pregnancy, you may notice some changes are occurring earlier. This is sometimes referred to as the “warming up” effect.

1) Fatigue

Most women are more tired than usual in early pregnancy. This feeling is understandable: Your body has a lot of work to do. During the first weeks of pregnancy, your body begins to produce more blood to carry nutrients to the fetus. Your heart multiplies its efforts to accommodate this increased blood flow, and your pulse quickens by as much as 10 to 15 beats per minute. Your body changes the way it uses water, protein, carbohydrate and fat. The combination of these profound changes translates into the fatigue you feel.

In addition to the physical changes that make you feel tired, you are also adjusting to new feelings and concerns. Whether your pregnancy was planned or unplanned, you may have conflicting feelings about it. Even if you are overjoyed at being pregnant, there are probably added emotional stresses in your life at this time. You may have fears about whether the baby will be healthy, anxiety about how you will adjust to motherhood, and concerns about increased expenses. If your work is demanding, you may worry about being able to sustain your productivity throughout pregnancy. These concerns are natural and normal. It is important to recognize that they also play a part in how you feel physically.

Controlling Fatigue
Rest. Try to get the rest you need. After the birth of your baby, your lifestyle is sure to change, and there are adjustments you can make even now. In addition to eating well and avoiding the harmful effects of smoking and alcohol, you should find ways to feel as rested as possible.

Take naps when you can during the day. At work, finding time to rest comfortably with your feet up can renew your energy. If you can’t nap during the day, maybe you can do so right after work, before dinner or evening activities. If you have a partner or other children, ask them to help as much as possible.

Also, cut down on social events if they are wearing you out. Those who care about you will understand and will be more than happy to make allowances for you. Ask for the support and understanding that you need during this time, keeping in mind that you will almost certainly have more stamina in later pregnancy.

If you need to go to bed at 6:30 or 7:00 to feel rested, do it. It may also help if you avoid drinking fluids for a few hours before bedtime so you won’t have to get up as frequently during the night to empty your bladder.

Exercise. One of the best ways to increase your energy level is to exercise. The more you exercise, the more energy you seem to have to continue exercising, as well as to perform your daily tasks. For example, walking for 30 minutes each day can really help you feel energized. See the Frequently Asked Questions-Exercise in Pregnancy for more guidance.

Eat well. Eating a balanced diet is even more important when you’re pregnant than it was before. The fatigue that is natural in early pregnancy can be aggravated if you’re not getting enough iron or protein. Check with your health care provider to make sure your diet is nutritious and balanced. Look at the Food Guide Pyramid.

2) Nausea and Vomiting (“Morning Sickness”)
“Morning sickness” can actually occur at any time of the day, and it affects nearly 3 out of 4 pregnant women. The symptoms of nausea and vomiting usually begin within the first month or two of the pregnancy and end 3-1/2 to 4 months into the pregnancy. Throughout your pregnancy, your body will continue to undergo tremendous physical, hormonal, and emotional change. Hormonal changes that come with pregnancy contribute somewhat, as do changes in your gastrointestinal system- the stomach empties a little more slowly under the influence of the hormones of pregnancy. Emotional stress and fatigue can also add to your feelings of “morning sickness.”

Morning sickness can be more severe in a first pregnancy, in young women and in women carrying multiple fetuses. Some women have nausea and vomiting beyond the first trimester, and a few even throughout their entire pregnancy. In rare instances, nausea and vomiting may be so severe that a pregnant woman cannot maintain proper nutrition and fluids or gain enough weight. This condition is known as hyperemesis gravidarum.

Controlling Nausea and Vomiting
Modify your eating habits. Eating smaller meals more frequently throughout the day often helps alleviate nausea. Drinking less fluid with meals may also provide relief. The reason for these measures is to avoid having your stomach completely empty or completely full, either of which can make nausea worse.

Eat morning snacks. If nausea is worse when you first wake up, try nibbling on soda crackers or sipping weak tea before you get out of bed. Rise slowly, allowing a little time to digest before you get up.

Rest. The fatigue that is so common in early pregnancy can also contribute to nausea. Additional sleep each night may help. Avoid displeasing smells and foods. Many women find certain smells or foods unpleasant when they are pregnant, even if they had no such reactions before. Whenever possible, try to avoid foods or smells that seem to aggravate your nausea.

Other Possible Remedies for Nausea and Vomiting:

  • It may be possible to alleviate nausea with an over-the-counter antacid. Speak to your healthcare provider first before taking these drugs. Some types of antacids can cause fluid buildup.
  • Vitamin B6 is believed to be a remedy for nausea. However, it is important to talk to your healthcare provider before taking a vitamin supplement during pregnancy.
  • Some women report success in using acupressure to combat nausea. Motion-sickness bands are one method of acupressure – they exert a steady pressure on the inside of the wrist.

3) Urinary Frequency
The increasing size of the uterus in the first trimester, along with more efficient functioning of the kidneys, may cause you to feel the need to urinate more often. You may also experience leaking of urine when sneezing, coughing or laughing. This is due to the growing uterus pressing against your bladder, which lies directly in front of and slightly under the uterus during the first few months of pregnancy. By the fourth month, the uterus will have expanded up out of the pelvic cavity, so that the pressure on your bladder is not as great.

Controlling Urinary Frequency
You may find that if you avoid drinking anything for a few hours before bedtime you will get up less often — and sleep better — throughout the night. It is not a good idea, though, to otherwise restrict your fluid intake during pregnancy.

Urinate as often as you feel the need. Holding in your urine can result in incomplete emptying of the bladder, which may in turn lead to a urinary tract infection. Leaning forward while you urinate will help to empty your bladder more fully. Completely emptying the bladder may also have the added benefit of cutting down on how often you need to urinate. If you leak urine throughout the day, wearing panty liners will make you more comfortable.

4) Breast Tenderness
The increased production of the hormones estrogen and progesterone is the primary reason for the changes in a pregnant woman’s breasts. After a few weeks of gestation, you may notice tingling sensations in your breasts, and they may feel heavy, tender and sore.

Controlling Breast Tenderness
A good support bra can help alleviate breast soreness. Try a maternity bra or a larger-sized athletic bra; they tend to be breathable and comfortable. If you have large breasts that make you uncomfortable at night, you might want to try wearing a bra while sleeping.

5) Headaches and Dizziness
Occasional headaches trouble many women in early pregnancy. The cause is uncertain, but like so many other discomforts of the first trimester, changes in your hormone levels and blood circulation may be factors. Other possible causes are the stress and fatigue that often accompany the emotional and physical adjustments to pregnancy. If you suddenly eliminated or cut down on caffeine once you learned you were pregnant, this change may also cause headaches for a few days.

Dizziness is common in pregnant women and can result from circulatory changes during pregnancy. Blood settles (pools) in the lower limbs more readily in pregnancy which makes the heart’s job of pumping blood to the brain more difficult. At times, the amount of blood may not be sufficient and lead to lightheadedness or even fainting. Stress, fatigue and hunger may also be causes of dizziness or faintness. Although headaches and dizziness at this point in your pregnancy may be nothing to be concerned about, call your doctor right away if these symptoms are persistent or severe. Migraine-like, throbbing headaches or fainting spells should also prompt you to call your doctor immediately.

Controlling Headaches and Dizziness
Sinus headaches can be soothed by applying warm compresses to the front and sides of your face, around your nose, eyes and temples. Applying a cold compress to the back of the neck may relieve tension headaches.

Relaxation exercises can help alleviate headaches as well as give you a greater overall sense of well being. These exercises may consist of simply closing your eyes and imagining a calm, peaceful scene. Eating well and getting enough rest and exercise are also important.

It is easier said than done, but minimizing the stresses in your life will help get you through the first trimester, as well as the rest of pregnancy. Some sources of stress, however, cannot be avoided. The key is to improve your coping skills. If you are under more stress than you feel you can handle, talking with a therapist or counselor, even if only on a one-time basis, can be very helpful.

Talk to your doctor before using pain relievers, even over-the-counter medications such as aspirin, ibuprofen, or naproxen sodium (Advil, Ibuprin, Motrin IB, Nuprin, Aleve). Acetaminophen (Aspirin Free Excedrin, Panadol, Tylenol) is a better choice during pregnancy, but it is best to avoid taking any medication during pregnancy unless absolutely necessary, and only when prescribed or advised by your doctor.

To prevent mild, occasional dizziness, move slowly as you get up from lying or sitting down. When on your feet, keep moving. By moving and contracting the leg muscles, you are helping force blood back to the heart. Try to keep your blood sugar level on an even keel by snacking occasionally on food such as dried or fresh fruit, whole-wheat bread, crackers or low-fat yogurt.

6) Weight Gain
Although you will probably gain about 25 to 30 pounds (11 to14 kilograms) during the course of your pregnancy, only a small percentage of this amount will be gained during the first trimester. You may experience few signs of pregnancy and gain only 3 to 4 pounds.

During the first trimester, you may find it difficult to believe you are pregnant. Yet, the first 3 months of pregnancy are critical to your baby’s health. During this time the baby will grow to 3 inches long and will have developed all of the major organs. Untreated illness or disease, radiation, or the use of tobacco, drugs, or alcohol during this time may harm your baby. Make sure you eat well, rest, and avoid taking any medication that has not been prescribed by your doctor. Tell any doctor, nurse, or dentist you visit that you are pregnant. Prenatal care, good nutrition, and adequate rest should be started immediately.

Glimpses at the First Trimester

First and Second Month
For the first eight weeks your developing baby is called an “embryo.” The heart, lungs, and brain begin to develop and the tiny heart beats by the 25th day. The embryo is enclosed in a sac of fluid to protect it from bumps and pressure. The baby will grow in this sac until birth. Your baby’s umbilical cord is also developing. This cord is made up of blood vessels that carry nourishment from your body to feed the baby and carry away the baby’s waste.

Gestational Age Five Weeks
At five weeks, your baby is about 1/17 of an inch long (1.5 mm). The embryo has divided into three layers from which tissues and organs will develop.

A groove, called the neural tube, has begun to take shape in the top layer, along the midline of the body. The brain, spinal cord, spinal nerves and backbone will develop from this region.

The middle layer of cells forms the beginnings of the heart and a primitive circulatory system – blood vessels, blood cells and lymph vessels. The foundations for bones, muscles, kidneys, and ovaries or testicles also develop from the middle layer of cells.

By the end of this week, the earliest blood elements and vessels have formed in the embryo and developing placenta. Circulation now begins, and the heart will develop rapidly. The circulatory system thus becomes the first functioning organ system.

The inner layer of cells will give rise to a simple tube, lined with mucous membranes, from which lungs, intestines and urinary bladder will develop. This week, however, there is little growth in the inner layer. Most of the growth that does occur is for the nervous and circulatory systems.

During this time you may not notice weight gain, but your breasts may be larger and may feel tender. You may also have some “morning sickness” or nausea. You should schedule your first prenatal exam during the first six weeks of pregnancy.

Gestational Age 7 weeks
Because the embryo is curled into a snug position is the uterus, it is difficult to measure the total length including the legs. It is easier and more common to measure a “crown-rump” length, the distance from the top of the head to the buttocks. At this stage, your baby is about 1 1/4 inches (3.2 cm) long from head to rump. It weighs less than 1/2 of an ounce (15 grams).

The beginnings of all the major body organs are formed. Bones of the skeleton are forming. Fingers have formed. The eyelids have grown, but the eyes look closed. The outer ears are forming.

Third Month
After eight weeks the embryo becomes a fetus, which means “young one.” Arms with tiny hands and fingers, and legs with the beginnings of knees, ankles, and toes begin to form. Organs such as the stomach and liver have also begun to develop. The head now appears very large compared to the rest of the body because the brain is growing rapidly. Tiny ears and the beginnings of hair are forming on the head.

By the end of the third month, your baby is about four inches long, weighs a little over an ounce, and signs of the baby’s sex are beginning to appear. Finger and toenails are developing. The mouth opens and closes and the baby will begin to move its hands, legs, and head. You will not yet be able to feel this movement.

You may have gained about three to four pounds and your clothes will begin to feel a little tight. You may also feel warmer than usual.

All organ systems are in place. Equally significant is the fact that the brain, nerves and muscles are starting to function. The palate has completely formed by the end of this period and the genitals are beginning to have male or female characteristics. The baby moves his or her body in jerks, flexing the arms and kicking the legs, but you won’t feel these movements until your baby grows a bit more.

For more information:

Go to the Pregnancy health topic.