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This topic covers pregnancy information, including planning for labor and delivery. If you aren't pregnant yet, see the topic Preparing for a Healthy Pregnancy.For more information on labor and delivery, see the topic Labor and Delivery.
What can you do to have a healthy pregnancy?
You may be happy and excited to find out that you're pregnant. And you may be a little nervous or worried. If this will be your first child, you may even feel overwhelmed by all of the things you need to know about having a baby. There is a lot to learn. But you don't have to know everything right away. You can read all about pregnancy now, or you can learn about each stage as your pregnancy goes on.
Pregnancy is measured in trimesters from the first day of your last menstrual period, totaling 40 weeks. Most babies are born at 37 to 42 weeks.
During your pregnancy, you'll have tests to watch for certain problems that could occur. With all the tests you'll have, you may worry that something will go wrong. But most women have healthy pregnancies. If there is a problem, these tests can find it early so that you and your doctor or midwife can treat it or watch it to help improve your chance of having a healthy baby.
Taking great care of yourself is the best thing you can do for yourself and your baby. Everything healthy that you do for your body helps your growing baby. Rest when you need it, eat well, and exercise regularly. Drink plenty of water before, during, and after you are active. This is very important when it's hot out.
You'll need to have regular checkups. At every visit, your doctor or midwife will weigh you and measure your belly to check your baby's growth. You'll also get blood and urine tests and have your blood pressure checked.
It's important to avoid tobacco smoke, alcohol and drugs, chemicals, and radiation (like X-rays). These can harm you and the baby.
What kinds of exams and tests will you have?
Your first prenatal exam gives your doctor or midwife important information for planning your care. You'll have a pelvic exam and urine and blood tests. You'll also have your blood pressure and weight checked. The urine and blood tests are used for a pregnancy test and to tell whether you have low iron levels (are anemic) or have signs of infection.
At each prenatal visit you'll be weighed, have your belly measured, and have your blood pressure and urine checked. Go to all your appointments. Although these quick office visits may seem simple and routine, your doctor is watching for signs of possible problems like high blood pressure.
In some medical centers, you can have screening in your first trimester to see if your baby has a chance of having Down syndrome or another genetic problem. The test usually includes a blood test and an ultrasound.
During your second trimester, you can have a blood test (triple or quadruple screen test) to see if you have a higher-than-normal chance of having a baby with birth defects. Based on the results of the tests, you may be referred to a geneticist for further discussion. Or you may have other tests to find out for sure if your baby has a birth defect.
Late in your second trimester, your blood sugar will be checked for diabetes during pregnancy (gestational diabetes). Near the end of your pregnancy, you will have tests to look for infections that could harm your newborn.
What changes can you expect in your body and your emotions?
You will go through some amazing changes during pregnancy. Your body, emotions, and relationships will all do some growing. These changes are common, but some may be a challenge.
Every woman feels these changes in her own way. Even the way she changes can change. In the beginning of your pregnancy, you may feel so tired that you can barely keep your head up. But at other times, you may have trouble sleeping.
Many women feel nauseated in the morning (morning sickness) or at other times of day in the early part of pregnancy. But some women never have this problem. Your breasts will get larger and may feel tender. Throughout your pregnancy, you may get heartburn or crave certain foods, and you may have aches and pains. You also may enjoy the flutters of your baby moving and kicking.
Your emotions may move around too. Even women who are happy about their pregnancy may worry a lot about their babies. They may even feel some sadness at the coming changes in their lifestyles.
Your relationship with your partner and other children you may have also may change. Talk with your partner and with your doctor if you have concerns about how you're feeling.
Health Tools help you make wise health decisions or take action to improve your health.
- Breastfeeding: Planning Ahead
- Fitness: Walking for Wellness
- Healthy Eating: Changing Your Eating Habits
- Healthy Eating: Cutting Unhealthy Fats From Your Diet
- Healthy Eating: Making Healthy Choices When You Shop
- Pregnancy and Diabetes: Planning for Pregnancy
- Pregnancy: Dealing With Morning Sickness
- Stress Management: Breathing Exercises for Relaxation
- Stress Management: Doing Guided Imagery to Relax
- Stress Management: Managing Your Time
Prenatal Visits and Tests
The first test you may have is the one you take at home to see if you're pregnant. After you know you're pregnant, you will have a series of tests throughout your pregnancy to make sure you and your baby are healthy.
At-home pregnancy test
If you think you might be pregnant, you can use a home pregnancy test as soon as you think you have missed your period.
Checkups and tests after you know you're pregnant
As soon as you know you're pregnant, make an appointment with your doctor or certified midwife. Your first prenatal visit will provide information that can be used to check for any problems as your pregnancy progresses. It's also a good time to think about how you want to partner with your doctor or midwife.
Good care during pregnancy includes regularly scheduled prenatal exams. At each prenatal visit, you'll be weighed, have your abdomen measured, and have your blood pressure and urine checked. Use this time to discuss with your doctor or midwife your list of pregnancy concerns or problems.
At different times in your pregnancy, you may have additional exams and tests performed. Although some are routine, others are only done when you ask for them, when a problem is suspected, or if you have a risk factor for a problem.
- Your first prenatal visit includes a health history, physical exam, and blood and urine tests.
- First-trimester exams and tests may include fetal ultrasound, which uses reflected sound waves to provide an image of your fetus and placenta.
- Second-trimester exams and tests may include fetal ultrasound and electronic fetal heart monitoring. Later in the second trimester, you will have an oral glucose screening test for possible gestational diabetes. If you have Rh-negative blood, you may have an antibody screening test and will receive an injection of Rh immunoglobulin. Screening tests help your doctor look for a certain disease or condition before any symptoms appear.
- Third-trimester exams and tests may include fetal ultrasound, hepatitis B screening, and group B strep screening.
Testing For Birth Defects
Tests in the first and second trimester can show if your baby has a birth defect. It's your choice whether to have these tests. You and your partner can talk to your doctor or midwife about birth defects tests.
To learn more about these tests, see the topic Birth Defects Testing.
You can choose from different kinds of tests. If you are worried about the chance of a birth defect, you might want test results as early as possible. If your risk for having a baby with a birth defect is very low or if knowing that your baby has a birth defect wouldn't change your plans, you might decide not to have early tests. Or you might choose not to have these tests at all.
Health and Nutrition
The best way to help yourself have a healthy pregnancy is to eat well, exercise regularly, get plenty of rest, and avoid things that could hurt your baby.
For more tips on how to have a healthy pregnancy, see Quick Tips: Healthy Pregnancy Habits.
- Try to get proper nutrition. Pay close attention to your folic acid, iron, and calcium intake and the need for slow, gradual weight gain. Women who are obese have a different weight-gain goal than other women.
- A vegetarian diet requires special attention so that you get enough protein, vitamin B12, vitamin D, and zinc, in addition to the extra folic acid, iron, and calcium that all expectant mothers need. These nutrients are vital to your fetus's cellular growth, brain and organ development, and weight gain.
- Calcium is an important nutrient, especially during pregnancy. If you can't or don't eat dairy products, you can get calcium in your diet from nonmilk sources such as tofu, broccoli, fortified orange juice or soy milk, greens, and almonds.
- Exercise during pregnancy can help your body best handle labor, delivery, and recovery. Moderate activity such as brisk walking or swimming is ideal during pregnancy. Some women enjoy prenatal yoga. Drink plenty of water before, during, and after you are active. This is very important when it's hot out.
- Do pelvic floor (Kegel) exercises during and after pregnancy. They strengthen your lower pelvic muscles. They may help prevent urine control problems (incontinence) after childbirth.
- In addition to moderate exercise, the following stretching and strengthening exercises are well suited to pregnancy:
What to avoid
- Medicines that are not approved by your doctor or midwife
- Alcohol and drugs
- Tobacco smoke
- Sources of food poisoning that may cause listeriosis or toxoplasmosis infection, such as raw meat, poultry, or seafood; unwashed fruits or vegetables; and cat feces or outdoor soil that cats commonly use
- Raw (unpasteurized) milk and cheeses made with raw milk
- Fish that contain high levels of mercury, such as shark, swordfish, king mackerel, marlin, orange roughy, bigeye tuna, or tilefish from the Gulf of Mexico.
- Hazardous chemicals, radiation, and certain cosmetic products
- Caffeine (or limit your intake to 1 cup of coffee or tea each day)
- Things that raise your core body temperature, such as doing hot yoga or using hot tubs and saunas
What's okay when you're pregnant
- Sex causes no problems during an uncomplicated pregnancy, and sexual interest often changes during different phases of a pregnancy.
- Working or going to school, if it isn't too physically demanding, is usually fine during pregnancy. Scale back if you're becoming too worn down as your pregnancy progresses. Talk to your doctor or midwife if you are at risk for preterm labor.
- Travel is usually a safe choice until later pregnancy. Talk to your doctor or midwife if you have any concerns. During your third trimester, it's best to stay within a few hours of a hospital, in case of sudden changes that need medical attention.
- Wearing a seat belt is vital to protect yourself and your baby during pregnancy.
- Massage during pregnancy is safe when it is done by a specially trained massage therapist.
Pregnancy is a time of many changes. Your body will go through a lot on the way to creating a new person.
Normal physical changes and symptoms throughout pregnancy
Although they can range from mild to severe, the following conditions are common during pregnancy:
- Morning sickness
- Sleep problems
- Breast changes
- Back pain and sciatica
- Pelvic ache and hip pain
- Leg cramps
Many pregnant women also have:
- Changes in vaginal discharge. A thin, milky-white discharge (leukorrhea) is normal throughout pregnancy. Also, the tissues lining the vagina become thicker and less sensitive during pregnancy.
- Nosebleeds and bleeding gums
- Hemorrhoids and constipation
- Varicose veins
- Hair changes
- Stretch marks, itchiness, and other skin changes
- Hand pain, numbness, or weakness (carpal tunnel syndrome)
- Mild swelling of your feet and ankles (edema).
The first trimester of pregnancy lasts from week 1 through week 12. Your first sign of pregnancy may be a missed menstrual period. Other early signs of pregnancy, caused by hormonal changes, include:
- Breast tenderness.
- Increased urination.
- Fullness or mild aching in your lower abdomen.
- Nausea with or without vomiting, also known as morning sickness.
The second trimester of pregnancy (from week 13 to week 27) is the time when most women start to look pregnant and may begin to wear maternity clothes. By 16 weeks, the top of your uterus, called the fundus, will be about halfway between your pubic bone and your navel. By 27 weeks, the fundus will be about 2 in. (5 cm) or more above your navel.
You may find that the second trimester is the easiest part of pregnancy. For some women, the breast tenderness, morning sickness, and fatigue of the first trimester ease up or disappear during the second trimester, while the physical discomforts of late pregnancy have yet to start. Pressure on your bladder may be less as the uterus grows up out of the pelvis.
Common symptoms you may experience during the second trimester of pregnancy include:
- Breast changes.
- Leg cramps.
- Back pain.
- Pelvic ache and hip pain.
- Stretch marks and other skin changes.
- Hemorrhoids and constipation.
- Heartburn (also a symptom of gastroesophageal reflux disease, or GERD).
- Nosebleeds and bleeding gums.
- Hand pain, numbness, or weakness (carpal tunnel syndrome).
- Braxton Hicks contractions, which are "warm-up" contractions that do not thin and open the cervix (do not lead to labor).
The third trimester lasts from week 28 to the birth. Many women have some discomfort during this time as their belly gets bigger. You might have trouble getting comfortable so you can sleep. And you might have a few other aches and pains.
Common symptoms you may experience during the third trimester include:
- Braxton Hicks contractions, which are "warm-up" contractions that do not thin and open the cervix (do not lead to labor).
- Back pain.
- Pelvic ache and hip pain.
- Hemorrhoids and constipation.
- Heartburn (a symptom of gastroesophageal reflux disease, or GERD).
- Hand pain, numbness, or weakness (carpal tunnel syndrome).
- Breathing difficulty, since your uterus is now just below your rib cage, and your lungs have less room to expand.
- Mild swelling of your feet and ankles (edema). Pregnancy causes more fluid to build up in your body. This, plus the extra pressure that your uterus places on your legs, can lead to swelling in your feet and ankles.
- Difficulty sleeping and finding a comfortable position. Lying on your back interferes with blood circulation, and lying on your stomach isn't possible. Sleep on your side, using pillows to support your belly and between your knees. Later in your pregnancy, it is best to lie on your left side. When you lie on your right side or on your back, the increasing weight of your uterus can partly block the large blood vessel in front of your backbone.
- Frequent urination, caused by your enlarged uterus and the pressure of the fetus's head on your bladder.
Pregnancy is measured in trimesters from the first day of your last menstrual period, totaling 40 weeks. The first trimester of pregnancy is week 1 through week 12, or about 3 months. The second trimester is week 13 to week 27. And the third trimester of pregnancy spans from week 28 to the birth.
Your baby will change from week to week. To learn more about how your baby is changing each month and about what tests you might think about having, see the Interactive Tool: From Embryo to Baby in 9 Months.
During the week after fertilization, the fertilized egg grows into a microscopic ball of cells (blastocyst), which implants on the wall of your uterus. This implantation triggers a series of hormonal and physical changes in your body.
The third through eighth weeks of growth are called the embryonic stage, during which the embryo develops most major body organs. During this process, the embryo is especially vulnerable to damaging substances, such as alcohol, radiation, and infectious diseases.
Having reached a little more than 1 in. (2.5 cm) in length by the ninth week of growth, the embryo is called a fetus. By now, the uterus has grown from about the size of a fist to about the size of a grapefruit.
The first trimester is a time of amazing development. The embryo starts out looking like a tiny seed, then a tadpole with a tail, and then more human.
If this is your first pregnancy, you'll begin to feel your fetus move at about 18 to 22 weeks after your last menstrual period. Although your fetus has been moving for several weeks, the movements have not been strong enough for you to notice until now. At first, fetal movements can be so gentle that you may not be sure what you are feeling.
If you've been pregnant before, you may notice movement earlier, sometime between weeks 16 and 18.
During this time, the fetus is still building up body fat and starting to put on a lot of weight. By the end of the second trimester, your fetus is about 10 in. (25.5 cm) long and weighs about 1.5 lb (680 g).
The third trimester of pregnancy spans from week 28 to the birth. The fetus moves frequently, especially between the 27th and 32nd weeks. After week 32, a fetus becomes too big to move around easily inside the uterus and may seem to move less.
Your due date marks the end of your 40th week. Most babies are born at 37 to 42 weeks. During this final trimester, your fetus grows larger and the body organs mature.
At the end of the third trimester, a fetus usually settles into a head-down position in the uterus. You will likely feel some discomfort as you get close to delivery.
Emotions and Relationships
The emotional experience of pregnancy is different for every woman. It's common to have mixed emotions and to feel uncertain—even if your pregnancy was planned.
Because of the increasing hormones and the fatigue of early pregnancy, mood swings can be worse than before pregnancy. Many women worry that their baby will have a problem. Or they may feel anxious about childbirth.
Your relationships with family and friends may change as you adjust to having a new family member.
- Emotional changes occur throughout pregnancy.
- Changes in your relationship with your partner are to be expected as your focus shifts to your own and your baby's well-being.
- Getting support from your partner is important to help you bond as a family and to help you have less stress.
- Handling pregnancy and parenting can be a challenge. Rest whenever you can. Prepare your other child or children ahead of time to help your family adjust to the demands of a newborn.
With all the changes in your life, you may feel stressed at times. Try relaxation exercises and use time management tips and skills at home.
Some women have health problems or concerns before they get pregnant. For other women, problems may come up during pregnancy. Your doctor or midwife will work with you to prevent or manage these problems to help you have a healthy pregnancy.
If you have a health problem or concern, you may have a high-risk pregnancy. This means that your doctor or midwife needs to follow you closely. It doesn't mean that something will go wrong during your pregnancy.
Pregnancy when you have health problems
- Depression during pregnancy requires treatment to reduce risks to you and your baby, before and after pregnancy.
- If you have diabetes, it's important during pregnancy to keep your blood sugar in your target range. Planning diabetes care before and during the first few weeks of pregnancy can lower your risk of problems.
- Obesity during pregnancy can increase the chance of problems. But most women who are obese have healthy babies. Your doctor will follow you closely and will plan a pregnancy weight gain that is right for you. Going on a diet during pregnancy is NOT recommended.
- If you have chronic high blood pressure during pregnancy, special care may be required. Your doctor may need to change the medicines you take to control your high blood pressure.
- Managing asthma during pregnancy is important for making sure you and your baby are getting enough oxygen. Most, but not all, asthma medicines are safe to use during pregnancy.
- Having epilepsy during pregnancy may require you to switch medicine or make other changes. But stopping medicine is not always the best solution. Having seizures during pregnancy can also harm the baby. Talk with your doctor about the best choice for you.
- Human immunodeficiency virus (HIV) during pregnancy requires early detection and treatment to prevent newborn infection.
- Cancer treatment during pregnancy is delayed whenever possible to prevent harm to the baby. But chemotherapy is sometimes used, when needed.
Common infections during pregnancy
- Vaginal yeast infections are more common in pregnancy because of the increased levels of hormones. Call your doctor or midwife if you have symptoms of a vaginal yeast infection or bacterial vaginal infection (bacterial vaginosis).
- Urinary tract infection is common during pregnancy and must be treated with antibiotics to prevent a dangerous infection or preterm labor.
- Bacterial vaginosis (BV) that causes symptoms is usually treated with oral antibiotics.
- Some women carry group B strep bacteria in their vaginal area. A woman can pass this infection to her baby during vaginal birth. This infection doesn't cause symptoms, but you will be screened for it in your third trimester.
Health problems that can happen during pregnancy
- Preeclampsia can develop after 20 weeks of pregnancy. It causes high blood pressure and protein in your urine. It can be very dangerous for the mother and baby. For more information, see the topic Preeclampsia and High Blood Pressure During Pregnancy.
- Gestational diabetes can make your baby grow too large, which can cause problems during delivery. To learn more, see the topic Gestational Diabetes.
- Preterm labor is the start of labor between week 20 and week 37 of pregnancy. The earlier the preterm labor, the greater the risk of problems with the baby. To learn more, see the topic Preterm Labor.
- Placenta previa happens when the placenta attaches in the wrong place in the uterus. To learn more, see the topic Placenta Previa.
- Placenta abruptio happens when the placenta separates too soon from the uterus. To learn more, see the topic Placenta Abruptio.
- If you have Rh-negative blood and your partner is Rh-positive, you need RhoGAM (Rh immunoglobulin) treatment to prevent Rh sensitization.
- The risk of blood clots can increase during pregnancy because of changes in hormones.
Other concerns during pregnancy
- Smoking during pregnancy increases the risk of problems such as low birth weight, preterm labor, and miscarriage.
- Pregnancy over age 35 poses some risks, but most older women have healthy pregnancies.
- Medicine use (including herbal remedies) during pregnancy should always be approved by your doctor or midwife, to prevent harm to the fetus.
- Immunizations help protect you and your baby from certain health problems. The flu vaccine and the tetanus, diphtheria, and pertussis (Tdap) vaccine are recommended for all pregnant women. It is safe to get these vaccines during your pregnancy. You may need to get other vaccines before or soon after your pregnancy.
- Pregnancy after bariatric surgery may mean that you keep seeing the doctor who did your weight-loss surgery, along with seeing the doctor or midwife who is caring for you during pregnancy.
- Domestic violence can happen more often and/or get worse when women are pregnant. It is dangerous for both the mother and the baby. For more information and to learn how to get help, see the topic Domestic Violence.
Planning for Labor
During your prenatal visits, talk with your doctor or midwife about what you would like to happen during your labor. Consider writing up your labor and delivery preferences in a birthing plan, either in a childbirth education class or on your own. You can find examples of birthing plans on parenting websites.
Because no labor or delivery can be fully anticipated or planned in advance, be flexible. Your experience after labor begins may be totally different from what you expected. If an emergency or an urgent situation arises, your plans may be changed for your own or your baby's safety.
When making plans for your baby's birth, consider the location of your delivery, who will deliver your baby, and whether you want continuous labor support from a doula, a friend, or family members. If you haven't already, this is also a good time to decide whether you'll attend a childbirth education class, starting in your sixth or seventh month of pregnancy.
Learn about labor and delivery ahead of time. Think through your preferences for comfort measures, pain relief, medical procedures, and fetal monitoring. And think through how you want to handle your first hours with your newborn. To learn more, see the topic Labor and Delivery.
Planning to breastfeed
Cord blood banking
Sometime during your pregnancy, you may get information about cord blood banking. Cord blood is the blood left in the umbilical cord after birth. Think about whether you want to bank your baby's umbilical cord blood for possible future use.
When to Call a Doctor
At any time during pregnancy
At any time during your pregnancy, call your doctor or midwife immediately if you:
- Have signs of preeclampsia, a potentially life-threatening condition, such as:
- Sudden swelling of your face, hands, or feet.
- Visual problems (such as dimness or blurring).
- Severe headache.
- Have pain, cramping, or fever with bleeding from the vagina.
- Pass some tissue from the uterus.
- Think or know you have a fever.
- Vomit more than 3 times a day or are too nauseated to eat or drink, especially if you also have fever or pain.
- Have an increase or gush of fluid from your vagina. It is possible to mistake a leak of amniotic fluid for a problem with bladder control.
At any time during your pregnancy, call your doctor or midwife today if you:
- Notice sudden swelling of your face, hands, or feet.
- Have any vaginal bleeding or an increase in your usual amount of vaginal discharge.
- Have pelvic pain that doesn't get better or go away.
- Have itching all over your body (usually in the evenings at first, then throughout the day as well) with or without dark urine, pale stools, or yellowing of skin or eyes.
- Have painful or frequent urination or urine that is cloudy, foul-smelling, or bloody.
- Feel unusually weak.
Between 20 and 37 weeks
If you are between 20 and 37 weeks pregnant, call 911 or other emergency services immediately if you:
- Experience severe vaginal bleeding.
- Have severe abdominal (belly) pain.
- Are in your third trimester and have had fluid gushing or leaking from your vagina (the amniotic sac has ruptured) AND you know or think the umbilical cord is bulging into your vagina (cord prolapse). If this happens, immediately get down on your knees so your buttocks are higher than your head to decrease pressure on the cord until help arrives. Cord prolapse can cut off the fetus's blood supply. (These measures apply to you if you are as early as 24 weeks pregnant.)
If you are between 20 and 37 weeks pregnant, call your doctor or midwife immediately or go to the hospital if you:
- Have signs of preterm labor, including:
- Mild or menstrual-like cramping with or without diarrhea.
- Regular contractions for an hour. This means about 6 or more contractions in 1 hour, even after you have had a glass of water and are resting.
- Unexplained low back pain or pelvic pressure.
- Have noticed that your baby has stopped moving or is moving much less than normal. See Pregnancy: Kick Counts for information on how to check your baby's activity.
- Have uterine tenderness or unexplained fever (possible symptoms of infection).
After 37 weeks
After 37 weeks, call 911 or other emergency services immediately if you:
- Have had fluid gushing or leaking from your vagina (the amniotic sac has ruptured) AND you know or think the umbilical cord is bulging into your vagina (cord prolapse). If this happens, immediately get down on your knees so your buttocks are higher than your head to decrease pressure on the cord until help arrives. Cord prolapse can cut off the fetus's blood supply. (These measures apply to you if you are as early as 24 weeks pregnant.)
After 37 weeks of pregnancy, call your doctor or midwife immediately or go the hospital if you:
- Have vaginal bleeding (for light spotting, you can call at any time on the same day).
- Have had regular contractions for an hour. This means about 4 or more in 20 minutes, or about 8 or more within 1 hour.
- Have a sudden release of fluid from the vagina.
- Notice that the baby has stopped moving or is moving much less than normal. See Pregnancy: Kick Counts for information on how to check your baby's activity.
To learn more about problems during pregnancy, see the topic Pregnancy-Related Problems.
- Health and Safety, Birth to 2 Years
- Alcohol Effects on a Fetus
- Premature Infant
- Alcohol or Drug Use During Pregnancy
- Growth and Development, Newborn
- Preterm Labor
- Medicines During Pregnancy
- Breech Position and Breech Birth
- Cesarean Section
- Vaginal Birth After Cesarean (VBAC)
- Multiple Pregnancy: Twins or More
- Asthma During Pregnancy
- Rh Sensitization During Pregnancy
- Avoiding Mercury in Fish
- Gestational Diabetes
- Placenta Abruptio
- Placenta Previa
- Fertility Awareness
Other Works Consulted
- American College of Obstetricians and Gynecologists (2010). Your Pregnancy and Birth, 5th ed. Washington, DC: American College of Obstetricians and Gynecologists.
- American College of Obstetricians and Gynecologists (2012). Update on immunization and pregnancy: Tetanus, diphtheria, and pertussis vaccination. ACOG Committee Opinion No. 521. Obstetrics and Gynecology, 119(3): 690–691.
- U.S. Department of Health and Human Services, U.S. Environmental Protection Agency (2011). Mercury Levels in Commercial Fish and Shellfish. Available online: http://www.fda.gov/Food/FoodSafety/Product-SpecificInformation/Seafood/FoodbornePathogensContaminants/Methylmercury/ucm115644.htm.