A full-term pregnancy lasts approximately 270 days (approximately 38.5 weeks) from conception to birth. Because it is easier to remember the first day of the last menstrual period (LMP) than to estimate the date of conception, obstetricians set the due date as 284 days (approximately 40.5 weeks) from the LMP. This assumes that conception occurred on day 14 of the woman’s cycle, which is usually a good approximation. The 40 weeks of an average pregnancy are usually discussed in terms of three trimesters, each approximately 13 weeks. During the second and third trimesters, the pre-pregnancy uterus—about the size of a fist—grows dramatically to contain the fetus, causing a number of anatomical changes in the mother (Figure).

Size of Uterus throughout Pregnancy

The uterus grows throughout pregnancy to accommodate the fetus.

Virtually all of the effects of pregnancy can be attributed in some way to the influence of hormones—particularly estrogens, progesterone, and hCG. During weeks 7–12 from the LMP, the pregnancy hormones are primarily generated by the corpus luteum. Progesterone secreted by the corpus luteum stimulates the production of decidual cells of the endometrium that nourish the blastocyst before placentation. As the placenta develops and the corpus luteum degenerates during weeks 12–17, the placenta gradually takes over as the endocrine organ of pregnancy.

The placenta converts weak androgens secreted by the maternal and fetal adrenal glands to estrogens, which are necessary for pregnancy to progress. Estrogen levels climb throughout the pregnancy, increasing 30-fold by childbirth. Estrogens have the following actions:

• They suppress FSH and LH production, effectively preventing ovulation. (This function is the biological basis of hormonal birth control pills.)
• They induce the growth of fetal tissues and are necessary for the maturation of the fetal lungs and liver.
• They promote fetal viability by regulating progesterone production and triggering fetal synthesis of cortisol, which helps with the maturation of the lungs, liver, and endocrine organs such as the thyroid gland and adrenal gland.
• They stimulate maternal tissue growth, leading to uterine enlargement and mammary duct expansion and branching.

Relaxin, another hormone secreted by the corpus luteum and then by the placenta, helps prepare the mother’s body for childbirth. It increases the elasticity of the symphysis pubis joint and pelvic ligaments, making room for the growing fetus and allowing expansion of the pelvic outlet for childbirth. Relaxin also helps dilate the cervix during labor.

The placenta takes over the synthesis and secretion of progesterone throughout pregnancy as the corpus luteum degenerates. Like estrogen, progesterone suppresses FSH and LH. It also inhibits uterine contractions, protecting the fetus from preterm birth. This hormone decreases in late gestation, allowing uterine contractions to intensify and eventually progress to true labor. The placenta also produces hCG. In addition to promoting survival of the corpus luteum, hCG stimulates the male fetal gonads to secrete testosterone, which is essential for the development of the male reproductive system.

The anterior pituitary enlarges and ramps up its hormone production during pregnancy, raising the levels of thyrotropin, prolactin, and adrenocorticotropic hormone (ACTH). Thyrotropin, in conjunction with placental hormones, increases the production of thyroid hormone, which raises the maternal metabolic rate. This can markedly augment a pregnant woman’s appetite and cause hot flashes. Prolactin stimulates enlargement of the mammary glands in preparation for milk production. ACTH stimulates maternal cortisol secretion, which contributes to fetal protein synthesis. In addition to the pituitary hormones, increased parathyroid levels mobilize calcium from maternal bones for fetal use.

As your uterus expands, you may feel aches and pains in the back, abdomen, groin area, and thighs. Many women also have backaches and aching near the pelvic bone due the pressure of the baby's head, increased weight, and loosening joints. Some pregnant women complain of pain that runs from the lower back, down the back of one leg, to the knee or foot. This is called sciatica. It is thought to occur when the uterus puts pressure on the sciatic nerve.

What might help:

• Lie down.
• Rest.
• Apply heat.

Call the doctor if pain does not get better.

A woman's breasts increase in size and fullness during pregnancy. As the due date approaches, hormone changes will cause your breasts to get even bigger to prepare for breastfeeding. Your breasts may feel full, heavy, or tender.

In the third trimester, some pregnant women begin to leak colostrum from their breasts. Colostrum is the first milk that your breasts produce for the baby. It is a thick, yellowish fluid containing antibodies that protect newborns from infection.

What might help:

• Wear a maternity bra with good support.
• Put pads in bra to absorb leakage.

Tell your doctor if you feel a lump or have nipple changes or discharge (that is not colostrum) or skin changes.

Women's cardiovascular systems in particular need to be resilient. As compared to a man's, a woman's body goes through extraordinary changes during her lifetime. These changes can have an enormous effect on her cardiovascular system. The most dramatic example of this is pregnancy.

These changes in the cardiovascular system develop primarily to meet the increased metabolic demands of the mother and fetus. Special demands are made upon the maternal heart, so a woman with a history of heart disease, heart murmur, hypertension, or rheumatic fever should talk with her doctor before she decides to become pregnant. A woman with congenital heart disease has a higher risk of having a baby with a heart defect and may need to have diagnostic tests performed.

Changes that occur, or may occur, during pregnancy include:

• Anemia. During pregnancy, blood volume increases by 40-50% but the number of red blood cells increases by only 20-30%, causing what's known as the anemia of pregnancy. This is not considered abnormal unless red blood cell levels fall too low.
• Varicose veins. Varicose veins may develop during pregnancy for a number of reasons. The additional volume of blood places additional pressure on the veins. As the uterus enlarges during pregnancy, it puts pressure on the inferior vena cava, the large vein on the right side of your body. This in turn increases pressure in the leg veins. In addition, during pregnancy progesterone levels rise, causing veins to relax. This may allow the two halves of the valves in the vein to separate slightly so that there is some backflow of blood into the vein, a condition termed venous insufficiency. Varicose veins generally appear on the legs, but during pregnancy varicose veins called hemorrhoids may also arise in the vagina and around the anus.
• Blood pressure. In a normal pregnancy, blood pressure never increases, in fact, it decreases slightly. Progesterone causes blood vessels to relax, giving them increased elasticity and facilitating circulation. By midpregnancy, diastolic pressure goes down somewhat, then returns to prepregnancy levels at about 36 weeks.
• Preeclampsia. The causes of preeclampsia, a serious complication also called pregnancy-induced hypertension, are unknown. Preeclampsia occurs only during pregnancy and the postpartum period and affects both the mother and the unborn baby. The mother's blood pressure rises, protein appears in the urine, and there may be water retention. These symptoms are probably caused by damage to the mother's blood vessels, liver, and kidney, possibly by substances from the placenta. Globally, preeclampsia is a leading cause of maternal and infant illness and death.
• Heart changes. The heart enlarges, works harder, and beats more rapidly. It must do this to compensate for the increased volume of blood, and also for the pressure placed on the lower aorta (located in the abdomen) and the inferior vena cava (found on the right side of body) by the enlarging uterus. The heart also changes position: the growing uterus causes the diaphragm to displace the heart, shifting it upward and to the left.

Many pregnant women complain of constipation. Signs of constipation include having hard, dry stools; fewer than three bowel movements per week; and painful bowel movements.

Higher levels of hormones due to pregnancy slow down digestion and relax muscles in the bowels leaving many women constipated. Plus, the pressure of the expanding uterus on the bowels can contribute to constipation.

What might help:

• Drink eight to 10 glasses of water daily.
• Don't drink caffeine.
• Eat fiber-rich foods, such as fresh or dried fruit, raw vegetables, and whole-grain cereals and breads.
• Try mild physical activity.

Tell your doctor if constipation does not go away.

Many pregnant women complain of dizziness and lightheadedness throughout their pregnancies. Fainting is rare but does happen even in some healthy pregnant women. There are many reasons for these symptoms. The growth of more blood vessels in early pregnancy, the pressure of the expanding uterus on blood vessels, and the body's increased need for food all can make a pregnant woman feel lightheaded and dizzy.

What might help:

• Stand up slowly.
• Avoid standing for too long.
• Don't skip meals.
• Lie on your left side.
• Wear loose clothing.

Call your doctor if you feel faint and have vaginal bleeding or abdominal pain.

During your pregnancy, you might feel tired even after you've had a lot of sleep. Many women find they're exhausted in the first trimester. Don't worry, this is normal! This is your body's way of telling you that you need more rest. In the second trimester, tiredness is usually replaced with a feeling of well being and energy. But in the third trimester, exhaustion often sets in again. As you get larger, sleeping may become more difficult. The baby's movements, bathroom runs, and an increase in the body's metabolism might interrupt or disturb your sleep. Leg cramping can also interfere with a good night's sleep.

What might help:

• Lie on your left side.
• Use pillows for support, such as behind your back, tucked between your knees, and under your tummy.
• Practice good sleep habits, such as going to bed and getting up at the same time each day and using your bed only for sleep and sex.
• Go to bed a little earlier.
• Nap if you are not able to get enough sleep at night.
• Drink needed fluids earlier in the day, so you can drink less in the hours before bed.

Hormones and the pressure of the growing uterus cause indigestion and heartburn. Pregnancy hormones slow down the muscles of the digestive tract. So food tends to move more slowly and digestion is sluggish. This causes many pregnant women to feel bloated.

Hormones also relax the valve that separates the esophagus from the stomach. This allows food and acids to come back up from the stomach to the esophagus. The food and acid causes the burning feeling of heartburn. As your baby gets bigger, the uterus pushes on the stomach making heartburn more common in later pregnancy.

What might help:

• Eat several small meals instead of three large meals — eat slowly.
• Drink fluids between meals — not with meals.
• Don't eat greasy and fried foods.
• Avoid citrus fruits or juices and spicy foods.
• Do not eat or drink within a few hours of bedtime.
• Do not lie down right after meals.

Call your doctor if symptoms don't improve after trying these suggestions. Ask your doctor about using an antacid.

Hemorrhoids are swollen and bulging veins in the rectum. They can cause itching, pain, and bleeding. Up to 50 percent of pregnant women get hemorrhoids. Hemorrhoids are common during pregnancy for many reasons. During pregnancy blood volume increases greatly, which can cause veins to enlarge. The expanding uterus also puts pressure on the veins in the rectum. Plus, constipation can worsen hemorrhoids. Hemorrhoids usually improve after delivery.

What might help:

• Drink lots of fluids.
• Eat fiber-rich foods, like whole grains, raw or cooked leafy green vegetables, and fruits.
• Try not to strain with bowel movements.
• Talk to your doctor about using products such as witch hazel to soothe hemorrhoids.

About 20 percent of pregnant women feel itchy during pregnancy. Usually women feel itchy in the abdomen. But red, itchy palms and soles of the feet are also common complaints. Pregnancy hormones and stretching skin are probably to blame for most of your discomfort. Usually the itchy feeling goes away after delivery.

What might help:

• Use gentle soaps and moisturizing creams.
• Avoid hot showers and baths.
• Avoid itchy fabrics.

Call your doctor if symptoms don't improve after a week of self-care.

At different times during your pregnancy, you might have sudden muscle spasms in your legs or feet. They usually occur at night. This is due to a change in the way your body processes calcium.

What might help:

• Gently stretch muscles.
• Get mild exercise.
• For sudden cramps, flex your foot forward.
• Eat calcium-rich foods.
• Ask your doctor about calcium supplements.

In the first trimester hormone changes can cause nausea and vomiting. This is called "morning sickness," although it can occur at any time of day. Morning sickness usually tapers off by the second trimester.

What might help:

• Eat several small meals instead of three large meals to keep your stomach from being empty.
• Don't lie down after meals.
• Eat dry toast, saltines, or dry cereals before getting out of bed in the morning.
• Eat bland foods that are low in fat and easy to digest, such as cereal, rice, and bananas.
• Sip on water, weak tea, or clear soft drinks. Or eat ice chips.
• Avoid smells that upset your stomach.

Call your doctor if you have flu-like symptoms, which may signal a more serious condition.

Call your doctor if you have severe, constant nausea and/or vomiting several times every day.

Nosebleeds and nasal stuffiness are common during pregnancy. They are caused by the increased amount of blood in your body and hormones acting on the tissues of your nose.

What might help:

• Blow your nose gently.
• Drink fluids and use a cool mist humidifier.
• To stop a nosebleed, squeeze your nose between your thumb and forefinger for a few minutes.

Call your doctor if nosebleeds are frequent and do not stop after a few minutes.

Feelings of swelling, tingling, and numbness in fingers and hands, called carpal tunnel syndrome, can occur during pregnancy. These symptoms are due to swelling of tissues in the narrow passages in your wrists, and they should disappear after delivery.

What might help:

• Take frequent breaks to rest hands.
• Ask your doctor about fitting you for a splint to keep wrists straight.

Stretch marks are red, pink, or brown streaks on the skin. Most often they appear on the thighs, buttocks, abdomen, and breasts. These scars are caused by the stretching of the skin, and usually appear in the second half of pregnancy.

Some women notice other skin changes during pregnancy. For many women, the nipples become darker and browner during pregnancy. Many pregnant women also develop a dark line (called the linea nigra) on the skin that runs from the belly button down to the pubic hairline. Patches of darker skin usually over the cheeks, forehead, nose, or upper lip also are common. Patches often match on both sides of the face. These spots are called melasma or chloasma and are more common in darker-skinned women.

What might help:

• Be patient — stretch marks and other changes usually fade after delivery.

Many women develop mild swelling in the face, hands, or ankles at some point in their pregnancies. As the due date approaches, swelling often becomes more noticeable.

What might help:

• Drink eight to 10 glasses of fluids daily.
• Don't drink caffeine or eat salty foods.
• Rest and elevate your feet.
• Ask your doctor about support hose.

Call your doctor if your hands or feet swell suddenly or you rapidly gain weight — it may be preeclampsia

Temporary bladder control problems are common in pregnancy. Your unborn baby pushes down on the bladder, urethra, and pelvic floor muscles. This pressure can lead to more frequent need to urinate, as well as leaking of urine when sneezing, coughing, or laughing.

What might help:

• Take frequent bathroom breaks.
• Drink plenty of fluids to avoid dehydration.
• Do Kegel exercises to tone pelvic muscles.

Call your doctor if you experience burning along with frequency of urination — it may be an infection

During pregnancy, blood volume increases greatly. This can cause veins to enlarge. Plus, pressure on the large veins behind the uterus causes the blood to slow in its return to the heart. For these reasons, varicose veins in the legs and anus (hemorrhoids) are more common in pregnancy.

Varicose veins look like swollen veins raised above the surface of the skin. They can be twisted or bulging and are dark purple or blue in color. They are found most often on the backs of the calves or on the inside of the leg.

What might help:

• Avoid tight knee-highs.
• Sit with your legs and feet raised.

The second and third trimesters of pregnancy are associated with dramatic changes in maternal anatomy and physiology. The most obvious anatomical sign of pregnancy is the dramatic enlargement of the abdominal region, coupled with maternal weight gain. This weight results from the growing fetus as well as the enlarged uterus, amniotic fluid, and placenta. Additional breast tissue and dramatically increased blood volume also contribute to weight gain (table below). Surprisingly, fat storage accounts for only approximately 2.3 kg (5 lbs) in a normal pregnancy and serves as a reserve for the increased metabolic demand of breastfeeding.

During the first trimester, the mother does not need to consume additional calories to maintain a healthy pregnancy. However, a weight gain of approximately 0.45 kg (1 lb) per month is common. During the second and third trimesters, the mother’s appetite increases, but it is only necessary for her to consume an additional 300 calories per day to support the growing fetus. Most women gain approximately 0.45 kg (1 lb) per week.

Did you know some problems due to pregnancy can happen up to a year after delivery? Be aware of urgent maternal warning signs and symptoms during pregnancy and in the year after delivery. Seek medical care immediately if you experience any signs or symptoms that are listed below. These symptoms could indicate a life-threatening situation.

The following list was developed by the Council on Patient Safety in Women’s Health Care. Learn about these urgent maternal warning signs below.

Headache that won’t go away or gets worse over time

• Feels like the worst headache of your life
• Lasts even after treatment with medication and fluid intake
• Starts suddenly with severe pain – like a clap of thunder
• Throbs and is on one side of your head above your ear
• Comes with blurred vision or dizziness

Dizziness or fainting

• You faint or pass out
• You have dizziness and lightheadedness that’s ongoing, or comes and goes over many days
• You experience a gap in time of which you have no memory

Changes in your vision

• You see flashes of light or bright spots
• You have blind spots or you can’t see at all for a short time
• Your vision is blurry, you can’t focus, or you’re seeing double

Fever of 100.4°F or higher

• You have a temperature of 100.4°F (38°C) or higher

Extreme swelling of your hands or face

• Swelling in your hands makes it hard to bend your fingers or wear rings
• Swelling in your face makes it hard to open your eyes all the way—they feel and look puffy
• Your lips and mouth feel swollen or you have a loss of feeling

This swelling is not like the usual slight swelling that most moms have during pregnancy, especially during the last few months of pregnancy.

Thoughts about harming yourself or your baby

• You may think about hurting yourself because you:
  • Feel very sad, hopeless, or not good enough
  • Don’t feel that you have control over your life
  • Feel extremely worried all the time
• You may think about hurting your baby and/or you may have scary thoughts that come when you don’t want or that are hard to get rid of

Trouble Breathing

• You feel short of breath suddenly or over time, as if you can’t breathe deeply enough to get enough air in your lungs
• Your throat and/or chest feel tight
• You have trouble breathing when you’re laying down flat, such as needing to prop your head up with pillows to sleep

Chest pain or fast-beating heart

• You have chest pain, such as:
  • A feeling of tightness or pressure in the center of your chest
  • Pain that travels to your back, neck, or arm
• You have a change in your heartbeat, such as:
  • A fast heartbeat or a pounding in your chest
  • An irregular heart rate or skipped heartbeats
• You feel dizzy, faint, or disoriented
• You have trouble catching your breath (talking and breathing are difficult)

These symptoms can happen at any time and anywhere or may be triggered by a specific event.

Severe nausea and throwing up

• You feel severely sick to your stomach (nauseous) beyond the normal queasy feeling and throwing up that many moms have in early pregnancy
• You are unable to drink for more than 8 hours or eat for more than 24 hours
• You throw up and can’t keep water or other fluids in your stomach
• You have:
  • A dry mouth
  • Headaches
  • Confusion
  • Fever
  • Dizziness or lightheadedness

Severe belly pain that doesn’t go away

• You have a sharp, stabbing, or cramp-like belly pain that doesn’t go away
• Your belly pain starts suddenly and is severe, or gets worse over time
• You have severe chest, shoulder, or back pain

Baby’s movement stopping or slowing during pregnancy

• You feel that your baby has stopped moving or your baby is moving less than before.

There is no specific number of movements that is considered normal, a change in your baby’s movement is what is important.

Vaginal bleeding or fluid leaking during pregnancy

• You have any bleeding from your vagina that is more than spotting – like a period
• You have fluid leaking out of your vagina
• You have vaginal discharge that smells bad

Vaginal bleeding or discharge after pregnancy

• You have heavy bleeding – soaking through one or more pads in an hour
• You pass clots bigger than an egg or you pass tissue
• You have vaginal discharge that smells bad

Severe swelling, redness or pain of your leg or arm

Anytime during pregnancy or up to 6 weeks after birth

• You have swelling, pain, or tenderness in your leg – usually your calf or in one leg:
  • It may or may not hurt when you touch it
  • It may hurt when you flex your foot to stand or walk
  • The painful area can also be red, swollen, and warm to the touch
• You have pain, tenderness or swelling in your arm, usually on just one side of your body

Overwhelming tiredness

• You are suddenly very tired and weak, not like chronic fatigue
• You don’t have enough energy to go about your day
• No matter how much you sleep, you don’t feel refreshed
• You feel so tired that you don’t get up to take care of your baby
• You feel sad after having your baby

This list is not meant to cover every symptom you might have. If you feel like something just isn’t right, or you aren’t sure if it’s serious, talk to your healthcare provider. Be sure to tell them if you are pregnant or were pregnant within the last year.

If you are pregnant or gave birth within a year, learn more about how to talk to your healthcare provider.