Though it may sound odd, your first week of pregnancy is based on the date of your last menstrual period. Your last menstrual period is considered week 1 of pregnancy, even if you weren’t actually pregnant yet.

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    The expected delivery date is calculated using the first day of your last period. For that reason, you may not have symptoms during the first few weeks of your 40-week pregnancy.

    From weeks 1 to 4, everything is still happening on a cellular level. The fertilized egg creates a blastocyst (a fluid-filled group of cells) that will develop into the fetus’s organs and body parts.

    About 10 to 14 days (week 4) after conception, the blastocyst will implant in the endometrium, which is the lining of the uterus. This can cause implantation bleeding, which may be mistaken for a light period. It does not occur for everyone. If it does occur, it will usually happen around the time you expect your period.

    Here are some signs of implantation bleeding:

    • Color. The color of each episode may be pink, red, or brown.
    • Bleeding. Implantation bleeding is usually much less than your usual period. It’s often described as light bleeding that never turns into a flow or enough to need a tampon.
    • Pain. Pain is usually milder than your usual menstrual pain. It may involve some cramping. It can be moderate or severe, but it’s most often mild.
    • Episodes. Implantation bleeding is likely to last less than 3 days and does not require treatment. It can sometimes last only a few hours.

    Tips

    If you think you may be experiencing implantation bleeding:

    • Avoid smoking, drinking alcohol, or using illegal drugs, all of which can be associated with heavy bleeding.
    • Do not use a tampon if you think you may be having implantation bleeding and not your usual period. Using a tampon could lead to a greater risk of infection.

    Once implantation is complete, your body will begin making human chorionic gonadotropin (hCG). This hormone helps the body maintain the pregnancy. It also tells the ovaries to stop releasing mature eggs each month.

    You will likely miss your next period 4 weeks after conception. If you typically have an irregular period, you’ll want to take a pregnancy test to confirm.

    Most home tests can detect hCG as soon as 8 days after a missed period. A pregnancy test will be able to detect hCG levels in your urine and show if you are pregnant.

    Tips

    • Take a pregnancy test to see if you’re pregnant.
    • If it’s positive, call a doctor or midwife to schedule your first prenatal appointment.
    • If you’re on any medications, ask your doctor whether they pose any risks to the pregnancy.

    A higher basal body temperature may be a sign of pregnancy. Your body’s core temperature may also increase more easily with exercise or in hot weather. During this time, make sure to drink more water and exercise cautiously.

    Fatigue can develop anytime during pregnancy. This symptom is common in early pregnancy. Your progesterone levels will soar, which can make you feel sleepy.

    Tips

    • The early weeks of pregnancy can make you feel exhausted. Try to get enough sleep if you can.
    • Keeping your bedroom cool can also help. Your body temperature may be higher during the early stages of pregnancy.

    Around weeks 8 to 10, your heart may begin pumping faster and harder. Palpitations and arrhythmias are common in pregnancy. This is normally due to hormones.

    According to a 2016 review of studies, your blood flow will increase between 30 and 50 percent during your pregnancy. This adds to your heart’s workload.

    You may have discussed any underlying heart issues with your medical team before conception. If not, now is the time to discuss any conditions or needed medications.

    Breast changes can occur between weeks 4 and 6. You’re likely to develop tender and swollen breasts due to hormone changes. This will likely go away after a few weeks when your body has adjusted to the hormones.

    Nipple and breast changes can also occur around week 11. Hormones continue to cause your breasts to grow. The areola — the area around the nipple — may change to a darker color and grow larger.

    If you’ve had bouts with acne before your pregnancy, you may experience breakouts again.

    Tips

    • Relieve breast tenderness by purchasing a comfortable, supportive maternity bra. A cotton, underwire-free bra is often the most comfortable.
    • Choose a bra with varying clasps that gives you more room to “grow” in the coming months.
    • Purchase breast pads that fit into your bra to reduce friction on your nipples and nipple pain.

    During pregnancy, your body increases the amount of blood it pumps. This causes the kidneys to process more fluid than usual, which leads to more fluid in your bladder.

    Hormones also play a large role in bladder health. During pregnancy, you may find yourself running to the bathroom more frequently or accidentally leaking.

    Tips

    • Drink about 300 milliliters (a little more than a cup) of extra fluids each day.
    • Plan out your bathroom trips ahead of time to avoid incontinence, or leaking urine.

    Similar to symptoms of a menstrual period, bloating may occur during early pregnancy. This may be due to hormone changes, which can also slow down your digestive system. You could feel constipated and blocked as a result.

    Constipation can also increase feelings of abdominal bloating.

    Nausea and morning sickness usually develop around weeks 4 to 6 and peak around week 9.

    Although it’s called morning sickness, it can occur anytime during the day or night. It’s unclear exactly what causes nausea and morning sickness, but hormones may play a role.

    During the first trimester of pregnancy, many women experience mild to severe morning sickness. It may become more intense toward the end of the first trimester, but often becomes less severe as you enter the second trimester.

    Tips

    • Keep a package of saltine crackers by your bed and eat a few before you get up in the morning to help settle morning sickness.
    • Stay hydrated by drinking plenty of water.
    • Call your doctor if you cannot keep fluids or food down.

    In most cases, high or normal blood pressure will drop in the early stages of pregnancy. This may also cause feelings of dizziness since your blood vessels are dilated.

    High blood pressure, or hypertension, as a result of pregnancy is more difficult to determine. Almost all cases of hypertension within the first 20 weeks indicate underlying problems. It may develop during early pregnancy, but it may also be present beforehand.

    A medical professional will take your blood pressure during your first doctor’s visit to help establish a baseline for a normal blood pressure reading.

    Tips

    • Consider switching to pregnancy-friendly exercises, if you haven’t already.
    • Learn how to track your blood pressure regularly.
    • Ask your doctor about personal dietary guidelines to help reduce high blood pressure.
    • Drink enough water and snack regularly to help prevent dizziness. Standing up slowly when getting up from a chair may also help.

    Smell sensitivity is a symptom of early pregnancy that’s mostly self-reported. There’s little scientific evidence about smell sensitivity during the first trimester. However, it might be important, since smell sensitivity may trigger nausea and vomiting. It may also cause strong distaste for certain foods.

    You may experience either a heightened or lessened sense of smell during pregnancy, according to 2017 research. This is especially common during the first and third trimesters. Heightened smell is more common than lessened smell. Some smells that never bothered you before may become less pleasing or even trigger nausea.

    The good news is that your sense of smell usually returns to normal after delivery, or within 6 to 12 weeks postpartum.

    Weight gain becomes more common toward the end of your first trimester. You may find yourself gaining about 1 to 4 pounds in the first few months.

    Calorie recommendations for early pregnancy won’t change much from your usual diet, but they will increase as pregnancy progresses.

    In the later stages, pregnancy weight often shows up in the:

    • breasts (about 1 to 3 pounds)
    • uterus (about 2 pounds)
    • placenta (1 1/2 pounds)
    • amniotic fluid (about 2 pounds)
    • increased blood and fluid volume (about 5 to 7 pounds)
    • fat (6 to 8 pounds)

    Hormones can cause the valve between your stomach and esophagus to relax. This allows stomach acid to leak, causing heartburn.

    Tips

    • Prevent pregnancy-related heartburn by eating several small meals a day instead of larger ones.
    • Try to stay sitting upright for at least an hour after eating to help your food digest.
    • If you need antacids, talk with a doctor about what may be safe during your pregnancy.

    Many people may begin saying you have the “pregnancy glow.” The combination of increased blood volume and higher hormone levels pushes more blood through your vessels. This causes the body’s oil glands to work overtime.

    The increased activity of your body’s oil glands gives your skin a flushed, glossy appearance. On the other hand, you may also develop acne.

    You can generally know if you’re pregnant 1 week after you’ve missed a period. The Office on Women’s Health in the U.S. Department of Health and Human Services says that taking a home pregnancy test at this point will give a more accurate result.

    Home pregnancy tests are inexpensive and widely available without a prescription in pharmacies and other stores.

    You can take a test earlier than this if you want, but you run the risk of getting a false negative result. This means the test may say you’re not pregnant, but in fact you are.

    If you take a home pregnancy test too early, there may not be enough hCG in your urine yet for the test to detect it. Home pregnancy tests work by testing the amount of hCG in your urine. This is a hormone that’s only present in the blood and urine of pregnant people.

    Also, every person’s body chemistry is a bit different. One person may get a positive result as early as a day after their period, while another person’s positive results may not show up for another week. So, early test results may not be the most accurate.

    Blood tests can often detect hCG earlier in a pregnancy than urine tests. Blood tests can sometimes give a positive result as early as 6 to 8 days after you ovulate, while urine tests do so about 3 weeks after ovulation.

    Unlike at-home urine tests, blood tests are usually done in a clinical setting. Contact your doctor if you want this type of test.

    Symptoms of pregnancy like nausea, fatigue, and breast tenderness sometimes occur even before you miss a period. These symptoms may give you an idea that you’re pregnant, but they are not sure proof. Only a test will tell for sure.

    Tips:

    • The Office on Women’s Health advises that if you get a negative result on a home pregnancy test, take another test a week later to recheck.
    • Some home pregnancy tests are more accurate than others. Here is a list of the best home pregnancy tests. Be sure to pick one that is known to be accurate.

    If you think you might be pregnant, the best time to take a home pregnancy test is 1 week after you first miss a period. According to the National Institute of Child Health and Human Development in 2017, home pregnancy tests are 97 percent accurate when used properly at the right time.

    A blood test can often reveal a pregnancy much earlier, but it must be done at a doctor’s office or in a clinical setting.

    If you get a positive result on a home pregnancy test, you should call your doctor right away, according to the Office on Women’s Health. The doctor can prescribe a more sensitive test and perform a pelvic exam to tell for certain if you’re pregnant.

    To keep you and the fetus healthy, the Office on Women’s Health recommends you see a medical professional as early as possible in your pregnancy. You can then schedule regular prenatal visits throughout your pregnancy.

    Your body will go through significant changes in early pregnancy. You may see signs such as nausea, breast tenderness, and, of course, the hallmark symptom of a missed period.

    If you think you might be pregnant, a good first step is to take a home pregnancy test. These tests are widely available without a prescription in pharmacies and other stores.

    If you receive a positive result, call a doctor for an appointment. They will perform an examination and a further test to confirm your pregnancy. You can then get started on a prenatal program to safeguard the health of you and the fetus.

    Read this article in Spanish.