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The First Trimester: A Guide to Early Pregnancy

By Stacey Feintuch
Reviewed by Alyssa Quimby, M.D. , Jessie Everts, Ph.D.
October 23, 2023
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Wow, you’re pregnant! The first trimester is the earliest phase of pregnancy; it runs from the first day of your last period to the end of your 13th week. While this time is exciting for some, it can be overwhelming for others (or full of mixed emotions). Here’s a guide to the first trimester of pregnancy.

Common First-Trimester Symptoms

Your body is changing in response to a rapid rise in hormones so it can carry a baby. Everyone experiences first-trimester symptoms in slightly different ways. These feelings can come and go, or they can last for weeks or months.

Breast Changes

Your breasts are already getting ready for breastfeeding thanks to a hike in the pregnancy hormones estrogen and progesterone. It’s common for breasts to be tender, swollen, or sensitive starting around week 7 or 8, says G. Thomas Ruiz, M.D., a board-certified ob-gyn and lead at MemorialCare Orange Coast Medical Center in Fountain Valley, California. Wearing a supportive bra can help. You’ll be more comfortable once your body adjusts to the hormonal shifts.

It’s also common for the areolas (the area around the nipples) to enlarge and darken, and they may be covered with small bumps. Veins under your breasts’ surface may become more noticeable, too.

Mood Swings

Even though you don’t have to deal with PMS right now, you may find yourself experiencing mood swings and irritability. That’s also because of the rush of pregnancy hormones, which should even out a bit more as your body adjusts to them.

Morning Sickness

Hormone surges can also cause you to feel nauseated or even to vomit starting around weeks 7 to 8, Ruiz says. Morning sickness can happen in the morning, when you have an empty stomach (hence its name), but it can occur at any time of day, he says.

Nausea during pregnancy can range from mild queasiness to severe food aversion that makes you vomit as soon as you smell it, Ruiz says. Some people can’t hold anything down, he adds.

“It’s a misconception that everyone has [morning sickness],” he says. “Some women don’t have it at all.”

It’s recommended to relieve nausea by eating small, low-fat meals more often; ginger-containing foods or drinks like ginger ale may help, too. Talk to your doctor if you can’t hold down any liquids or if you’ve lost more than 5 pounds.

Increased urination

Your uterus is growing and putting pressure on your bladder, so you may find you’ll make more bathroom trips starting around weeks 10 to 13, Ruiz says. Plus, your body’s blood volume is rising, so your kidneys have to excrete more fluid, causing frequent urination.

Fatigue

Your progesterone levels are increasing, which can cause you to feel extra tired. Napping during this time and/or going to bed extra early are normal and expected. Keep your energy as high as you can by eating right, exercising, and getting plenty of rest.

Heartburn

Hormones can relax the valve between your esophagus and stomach. That allows stomach acid to rise, triggering heartburn. It may help to eat smaller meals more frequently and to avoid spicy or fried foods as well as citrus fruits and chocolate.

Constipation

Food may move more slowly through your digestive system as a result of high progesterone levels. That causes constipation. To help get things moving, eat plenty of fiber and drink lots of water. Drinking prune or other fruit juices may help, as well.

​​​​If you’re still struggling with constipation, talk to your doctor about over-the-counter medications you can use that are safe.

First-Trimester Mental Health

You may be dealing with some extreme emotions as you adjust to the idea of being pregnant.

“If you were trying to get pregnant, you may be ecstatic. You’ve been trying, and you get that positive test, and you’re ecstatic,” Ruiz says. “Then, you have the other end. You may not have been using contraception, or not using it properly, and then discover you’re pregnant. I see both shock and sadness versus happiness.” He adds that some people may not be sure how to feel about becoming pregnant, and that’s completely normal, too.

Many people don’t feel ready to share the news of their pregnancy in the first trimester. This may leave you feeling isolated, like you don’t have anyone to talk to about what you’re going through.

Feelings of anxiety are also common in early pregnancy, says Wendy Goodall McDonald, M.D., a board-certified ob-gyn at Women’s Health Consulting in Chicago. Some people are worried about losing the pregnancy. Others feel anxious about the potentially unsafe things they did before they found out they were pregnant, such as drinking alcohol or getting X-rays.

“You can’t go back in time,” McDonald says. She reassures her patients that whatever they did before they knew they were pregnant likely won’t affect the pregnancy. If things are looking good at your prenatal visits, hold on to that. Take a deep breath and try not to be concerned about where you went or what you did, she says.

Women may also feel guilty for getting pregnant if they have friends who are struggling to conceive a child, or if they feel fine when others are struggling with morning sickness, says McDonald.

Some people wonder why they don’t “feel pregnant” or don’t really feel extreme emotions at all, and wonder if that’s normal. “It’s okay not to feel glorious, happy, and euphoric in the first trimester,” McDonald says. Or maybe you just don’t feel well physically, making it hard for you to be overjoyed right now. “You feel guilty when you don’t automatically feel joy and happiness.”

There’s no one way to feel during pregnancy. Your feelings are valid, and you’re certainly not the only one feeling the way you do right now. To help you through any difficulties, you can contact a mental health professional. Postpartum Support International has a directory where you can find therapists who specialize in mental health during pregnancy and postpartum. You can find additional support from others in the pregnancy community.

First-Trimester Doctor Appointments

You may assume that your doctor will want to see you as soon as you get a positive pregnancy test result. But the ideal time for your first prenatal doctor visit is usually about seven to nine weeks after your last menstrual period, Ruiz says. Your doctor will likely want you to go in sooner if you have a history of ectopic pregnancy, bleeding, or miscarriage.

Your first prenatal visit will focus on your overall health. This first visit tends to be one of the longest. It’s your doctor’s opportunity to find out a lot about you and your medical history. There is also a lot of education that goes on during this visit and an opportunity for you to ask questions.

Your doctor will take a medical history as well as record your blood pressure, height, weight, and date of your last period. They’ll do a pelvic exam and ask about your history of miscarriage or abortions, hospitalizations, medications, medical issues, and your family’s medical history. You’ll likely discuss dental care, travel limits, caffeine consumption, prenatal vitamins, diet and nutrition, and exercise, too.

At this first appointment, you’ll typically have an ultrasound to determine whether the pregnancy is progressing normally. The first ultrasound checks to make sure the pregnancy is in the correct location, looks for a heartbeat, and can tell you if you’re having more than one baby.

Your doctor will also review your vaccination history and discuss vaccines that are recommended in pregnancy, such as the flu shot and the COVID-19 vaccine. This is a great time to discuss any concerns you have with your doctor and get your questions about vaccines answered.

After that, the visits tend to be a bit shorter and are scheduled about every four weeks until you’re 28 weeks pregnant, in most cases. Checkups help your doctor keep tabs on exactly how you and your baby are doing. At each of those appointments, the doctor will typically check your weight and blood pressure as well as your baby’s heartbeat.

First-Trimester Screenings and Tests

Certain screenings and tests are typically given during the first trimester to gauge the health of you and your baby.

Pap Test

Your doctor will do a Pap test (also known as a Pap smear) if you’re due for this or don’t remember when it was last done. This is to see if you have any abnormal cells on your cervix that could lead to cervical cancer.

McDonald says that patients often question whether this test is safe. She says it is, adding, “We wouldn’t do anything that’s unsafe.” She says that this test touches a part of the cervix that is far away from the baby. It’s common to spot or bleed a bit after getting a Pap test during pregnancy, she says. But that’s not a sign of a problem.

Urine Tests

Urine tests will be done early in pregnancy to screen for bacteria, glucose, and proteins, which could be signs of issues that would need to be treated or monitored, such as a urinary tract infection (UTI) or gestational diabetes.

Blood Tests

Your blood will be tested for several different things:

  • Blood type: It’s helpful for your doctor to know whether you’re A, B, AB, or O.
  • Rh factor: Everyone’s blood is either Rh negative or Rh positive. When a mom’s blood is Rh negative and the baby’s is Rh positive, then doctors will need to take certain steps to prevent problems that could result.
  • Immunity: It’s important to know whether you’re immune to diseases that could affect pregnancy, such as rubella (German measles) and chickenpox.
  • Hemoglobin: If the oxygen-carrying power of your red blood cells looks low, you’ll be treated for anemia with an iron supplement.
  • Infectious diseases: Your doctor will test for any sexually transmitted diseases or sexually transmitted infections that need to be treated, like HIV, gonorrhea, chlamydia, or syphilis, says McDonald.
  • Complete blood count: A complete blood count (CBC) is a blood test that can assess your overall health and detect a range of disorders, including anemia, says McDonald.

Noninvasive Prenatal Testing (NIPT)

The NIPT is a blood test used to screen for a baby’s risk of chromosomal conditions, such as trisomy 13, 18, and 21 (Patau syndrome, Edwards syndrome, and Down syndrome, respectively), says Ruiz. “It’s very effective and reliable at identifying these,” he says. The results of this test may help you decide whether you want further testing or to weigh your options if the risk is high.

NIPT can also tell you your fetus’s sex, if you want to find out.

Nuchal Translucency (NT) Ultrasound

The NT is a specialty ultrasound performed between 11 and 14 weeks that helps to screen for chromosome defects. It’s offered to the majority of pregnant women even if you opt not to have NIPT testing done. This is typically an ultrasound you’re referred for and is usually done at a specialty ultrasound center or hospital rather than your doctor’s office.

Fetal Development in the First Trimester

Even though you may not look pregnant, dramatic changes are happening in your body in the first trimester.

In the first four weeks, your developing baby, called an embryo, will resemble a tadpole. Major systems and organs will start to form. Ears and eyes will develop, and limb buds will appear, which will form into arms and legs later. The heart will beat.

By the end of eight weeks, the embryo will better resemble a human, with a head that’s bigger in proportion to the body. Major body systems will develop and even start working. The eyes, nose, and ears will continue to develop, too. Stumps of arms and legs will form along with a distinct heart. Fingers and toes will be webbed, and bones are developing. The mouth will form tooth buds, which will later become baby teeth. After week 8, your embryo will be known as a fetus.

From weeks 9 to 12, eyelids will form, and fingernails and toenails will appear. Arms and legs will become more fully developed. External genitals will form. Even the voice box will begin to develop. “Now, it looks like a classic picture of a baby,” Ruiz says.

However, there’s still two-thirds left to your pregnancy. “All the major organs are developing by 13 to 14 weeks,” McDonald says. “But it’s not enough for the baby to survive outside yet.”

Now that you know all about the physical and mental changes of the first trimester, as well as how your baby is growing and developing, you probably want to know what’s happening next. Read up on what’s in store for you in our guide to the second trimester.

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