First trimester what to expect

The First Trimester | Johns Hopkins Medicine

What You Need to Know

At your first prenatal visit, you will undergo a physical exam as well as certain tests and screenings to assess the health of you and your unborn baby.
First trimester symptoms vary from woman to woman, with some experiencing all known symptoms and others only a few. Duration of symptoms can vary as well.
After eight weeks, the embryo is referred to as a fetus.
Although the fetus is only 1 to 1.5 inches long at this point, all major organs and systems have been formed.
During the first trimester, the fetus is most susceptible to damage from substances, like alcohol, drugs and certain medicines, and illnesses, like rubella (German measles).

Your First Prenatal Visit

Your first prenatal visit is the most thorough. A complete medical history is taken, a physical exam is done, and certain tests and procedures are performed to assess the health of both you and your unborn baby. Your first prenatal visit may include:

Personal medical history. This may include taking record of any of the following:
- Previous and current medical conditions, like diabetes, high blood pressure (hypertension), anemia and/or allergies
- Current medicines (prescription, over-the-counter and nutritional supplements)
- Previous surgeries
Maternal and paternal family medical history, including illnesses, intellectual or developmental disabilities, and genetic disorders, like sickle cell disease or Tay-Sachs disease
Personal gynecological and obstetrical history, including past pregnancies (stillbirths, miscarriages, deliveries, terminations) and menstrual history (length and duration of menstrual periods)
Education, including a discussion regarding the importance of proper nutrition and expected weight gain in pregnancy; regular exercise; the avoidance of alcohol, drugs and tobacco during pregnancy; and a discussion of any concerns about domestic violence
Pelvic exam. This exam may be done for one or all of the following reasons:
- To note the size and position of the uterus
- To determine the age of the fetus
- To check the pelvic bone size and structure
- To perform a Pap test (also called Pap smear) to find the presence of abnormal cells
Lab tests, including the following:
- Urine tests. These are done to screen for bacteria, glucose and protein.
- Blood tests. These are done to determine your blood type.
  - All pregnant women are tested for the Rh factor during the early weeks of pregnancy. Rh incompatibility happens when the mother’s blood is Rh-negative, the father’s blood is Rh-positive and the fetus’ blood is Rh-positive. The mother may make antibodies against the Rh-positive fetus, which may lead to anemia in the fetus. Incompatibility problems are watched and appropriate medical treatment is available to prevent the formation of Rh antibodies during pregnancy. There are also other blood antibodies that may cause problems in pregnancy that are screened for on the first visit.
Blood screening tests. These are done to find diseases that could have an effect on the pregnancy. One example is rubella, an infectious disease that is also called German measles.
Genetic tests. These are done to find inherited diseases, like sickle cell disease and Tay-Sachs disease.
Other screening tests. These are performed to find infectious diseases, like sexually transmitted diseases and urinary tract infections.

The first prenatal visit is also an opportunity to ask any questions or discuss any concerns that you may have about your pregnancy.

The First Trimester: What to Expect

A healthy first trimester is crucial to the normal development of the fetus. You may not be showing much on the outside yet, but on the inside, all of the major body organs and systems of the fetus are forming.

As the embryo implants itself into the uterine wall, several developments take place, including the formation of the:

Amniotic sac. A sac filled with amniotic fluid, called the amniotic sac, surrounds the fetus throughout the pregnancy. The amniotic fluid is liquid made by the fetus and the amnion (the membrane that covers the fetal side of the placenta) that protects the fetus from injury. It also helps to regulate the temperature of the fetus.
Placenta. The placenta is an organ shaped like a flat cake that only grows during pregnancy. It attaches to the uterine wall with tiny projections called villi. Fetal blood vessels grow from the umbilical cord into these villi, exchanging nourishment and waste products with your blood. The fetal blood vessels are separated from your blood supply by a thin membrane.
Umbilical cord. The umbilical cord is a ropelike cord connecting the fetus to the placenta. The umbilical cord contains two arteries and a vein, which carry oxygen and nutrients to the fetus and waste products away from the fetus.

It is during this first trimester that the fetus is most susceptible to damage from substances, like alcohol, drugs and certain medicines, and illnesses, like rubella (German measles).

During the first trimester, your body and your baby’s body are changing rapidly.

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The First Trimester: Changes to Your Body

During pregnancy, many changes will happen to your body to help nourish and protect your baby. Women experience these changes differently. Some symptoms of pregnancy continue for several weeks or months. Others are only experienced for a short time. Some women experience many symptoms, and other women experience only a few or none at all. The following is a list of changes and symptoms that may happen during the first trimester:

The mammary glands enlarge, causing the breasts to swell and become tender in preparation for breast-feeding. This is due to an increased amount of the hormones estrogen and progesterone. A supportive bra should be worn.
Your areolas (the pigmented areas around each breast’s nipple) will enlarge and darken. They may become covered with small, white bumps called Montgomery’s tubercles (enlarged sweat glands).
Veins become more noticeable on the surface of your breasts.
The uterus is growing and begins to press on your bladder. This causes you to need to urinate more often.
Partly due to surges in hormones, you may experience mood swings similar to premenstrual syndrome, a condition experienced by some women that is characterized by mood swings, irritability and other physical symptoms that happen shortly before each menstrual period.
Increased levels of hormones to sustain the pregnancy may cause “morning sickness,” which causes nausea and sometimes vomiting. However, morning sickness does not necessarily happen just in the morning and rarely interferes with proper nutrition for the mother and her fetus.
Constipation may happen as the growing uterus presses on the rectum and intestines.
The muscular contractions in the intestines, which help to move food through the digestive tract, are slowed due to high levels of progesterone. This may, in turn, cause heartburn, indigestion, constipation and gas.
Clothes may feel tighter around the breasts and waist, as the size of the stomach begins to increase to accommodate the growing fetus.
You may experience extreme tiredness due to the physical and emotional demands of pregnancy.
Cardiac volume increases by about 40 to 50 percent from the beginning to the end of the pregnancy. This causes an increased cardiac output. An increased cardiac output may cause an increased pulse rate during pregnancy. The increase in blood volume is needed for extra blood flow to the uterus.

The First Trimester: Fetal Development

The most dramatic changes and development happen during the first trimester. During the first eight weeks, a fetus is called an embryo. The embryo develops rapidly and by the end of the first trimester, it becomes a fetus that is fully formed, weighing approximately 0.5 to 1 ounce and measuring, on average, 3 to 4 inches in length.

First Trimester Fetal Growth and Development Benchmarks

The chart below provides benchmarks for most normal pregnancies. However, each fetus develops differently.

Timing	Development Benchmark
By the end of four weeks	All major systems and organs begin to form. The embryo looks like a tadpole. The neural tube (which becomes the brain and spinal cord), the digestive system, and the heart and circulatory system begin to form. The beginnings of the eyes and ears are developing. Tiny limb buds appear, which will develop into arms and legs. The heart is beating.
By the end of eight weeks	All major body systems continue to develop and function, including the circulatory, nervous, digestive, and urinary systems. The embryo is taking on a human shape, although the head is larger in proportion to the rest of the body. The mouth is developing tooth buds, which will become baby teeth. The eyes, nose, mouth, and ears are becoming more distinct. The arms and legs can be easily seen. The fingers and toes are still webbed, but can be clearly distinguished. The main organs continue to develop and you can hear the baby's heartbeat using an instrument called a Doppler. The bones begin to develop and the nose and jaws are rapidly developing. The embryo is in constant motion but cannot be felt by the mother.
From embryo to fetus	After 8 weeks, the embryo is now referred to as a fetus, which means offspring. Although the fetus is only 1 to 1.5 inches long at this point, all major organs and systems have been formed.
During weeks nine to 12	The external genital organs are developed. Fingernails and toenails appear. Eyelids are formed. Fetal movement increases. The arms and legs are fully formed. The voice box (larynx) begins to form in the trachea.

The fetus is most vulnerable during the first 12 weeks. During this period of time, all of the major organs and body systems are forming and can be damaged if the fetus is exposed to drugs, infectious agents, radiation, certain medications, tobacco and toxic substances.

Even though the organs and body systems are fully formed by the end of 12 weeks, the fetus cannot survive independently.

What to Expect, Baby Development

Written by Stephanie Watson

Reviewed by Traci C. Johnson, MD on August 12, 2022

What Is the First Trimester of Pregnancy?

The first trimester is the earliest phase of pregnancy. It starts on the first day of your last period -- before you’re even actually pregnant -- and lasts until the end of the 13th week. It’s a time of great anticipation and of rapid changes for both you and your baby. Knowing what to expect will help you get ready for the months ahead.

First Trimester Changes in Your Body

Pregnancy is different for every woman. Some women glow with good health during those first 3 months; others feel absolutely miserable. Here are some of the changes you might notice, what they mean, and which signs warrant a call to your doctor.

Bleeding. About 25% of pregnant women have slight bleeding during their first trimester. Early in the pregnancy, light spotting may be a sign that the fertilized embryo has implanted in your uterus. But if you have severe bleeding, cramping, or sharp pain in your belly, call the doctor. These could be signs of a miscarriage or ectopic pregnancy (a pregnancy in which the embryo implants outside of the uterus).

Breast tenderness.Sore breasts are one of the earliest signs of pregnancy. They're triggered by hormonal changes, which are getting your milk ducts ready to feed your baby. Your breasts will probably be sore throughout the first trimester. Going up a bra size (or more) and wearing a support bra can make you feel more comfortable. You probably won’t go back to your regular bra size until after your baby is finished nursing.

Constipation. During pregnancy, high levels of the hormone progesterone slow down the muscle contractions that normally move food through your system. Add to that the extra iron you're getting from your prenatal vitamin, and the result is uncomfortable constipation and gas that can keep you feeling bloated throughout your pregnancy. Eat more fiber and drink extra fluids to keep things moving more smoothly. Physical activity can also help.

If your constipation is really bothering you, talk to your doctor about what mild laxative or stool softeners are safe to use during pregnancy.

Discharge. It's normal to see a thin, milky white discharge (called leukorrhea) early in your pregnancy. You can wear a panty liner if it makes you feel more comfortable, but don't use a tampon because it could put germs into your vagina. If the discharge smells really bad, if it’s green or yellow, or if there's a lot of clear discharge, call the doctor.

Fatigue. Your body is working hard to support a growing baby. That means you’ll get tired more easily than usual. Take naps or rest when you need to during the day. Make sure you're getting enough iron. Too little can lead to anemia, which can make you even more tired.

Food likes and dislikes. Although you may not want a bowl of mint chip ice cream topped with dill pickles, as the old stereotype goes, your tastes can change while you're pregnant. More than 60% of pregnant women have food cravings. More than half have foods they really don’t like. Giving in to cravings from time to time is OK, so long as you eat healthy, low-calorie foods most of the time. The exception is pica -- a craving for nonfoods like clay, dirt, and laundry starch, which can be dangerous for you and your baby. If you experience this kind of craving, report it to your doctor right away.

Peeing a lot. Your baby is still pretty small, but your uterus is growing and it's putting pressure on your bladder. As a result, you may feel like you have to go to the bathroom all the time. Don't stop drinking fluids -- your body needs them -- but do cut down on caffeine (which stimulates your bladder), especially before bedtime. When nature calls, answer it as soon as you can. Don't hold it in.

Heartburn. During pregnancy, your body produces more of the hormone progesterone. It relaxes smooth muscles, like the ring of muscle in your lower esophagus, the tube that connects your mouth and stomach. These muscles normally keep food and acids down in your stomach. When they loosen up, you can get acid reflux, otherwise known as heartburn. To avoid the burn:

Eat a few small meals throughout the day.
Don't lie down right after you eat.
Avoid greasy, spicy, and acidic foods (like citrus fruits).
Try raising your pillows when you sleep.

Mood swings. Increased fatigue and changing hormones can put you on an emotional roller coaster that takes you from joyous to miserable, or from hopeful to terrified in a matter of seconds. It's OK to cry, but if you feel overwhelmed, try to find an understanding ear. You can talk to your partner, a friend, a family member, or even a professional.

Morning sickness.Nausea is one of the most common pregnancy symptoms. Up to 85% of pregnant women have it. It results from hormone changes in your body and it can last through the entire first trimester. For some pregnant women, nausea is mild. Others can't start their day without vomiting. Nausea is usually worse in the morning (hence the name, "morning sickness"). To calm your nausea, try eating small, bland, or high-protein snacks (crackers, meat, or cheese) and sipping water, clear fruit juice (apple juice), or ginger ale. You may want to even do this before you get out of bed. Avoid any foods that make you sick to your stomach. Nausea itself isn't anything to worry about, but if it’s severe or just won’t go away, it can affect the amount of nutrition your baby gets. Call your doctor if you can't stop throwing up or can't keep down any food.

Weight gain. Pregnancy is one of the few times in a woman's life when weight gain is considered a good thing, but don't overdo it. During the first trimester, you should gain about 3-6 pounds (your doctor may suggest you adjust your weight gain up or down if you started your pregnancy underweight or overweight). Although you're carrying an extra person, you really aren’t eating for two. You only need about an extra 150 calories a day during the first trimester. Get those calories the healthy way, by adding extra fruits and vegetables, milk, whole-grain bread, and lean meat to your diet.

Baby’s Growth in the First Trimester

During the first 13 weeks, your baby changes from a fertilized egg into a fully-formed fetus. All the major organs and systems are taking shape. That means your baby could be harmed if you use street drugs, have an illness, or get exposed to radiation. Here’s what’s happening:

The fertilized egg becomes a cluster of rapidly dividing cells that implants in your uterus. The placenta, umbilical cord and amniotic sac all start to grow.
Your baby’s nervous system changes from an open neural tube to a brain and spinal cord. Nerves and muscles start working together. Your baby can move on its own, but it’s too soon for you to feel it.
The heart takes shape and begins to beat. You can hear it on ultrasound as early as week 6. It beats 120 to 160 times per minute. Red blood cells are forming.
Your baby develops a digestive system, including intestines and kidneys.
They have lungs and other major organs, but they’re not fully developed.
A soft skeleton is starting to grow.
Your baby starts to look like a baby, with arms, legs, fingers, and toes. Their face gets eyes, ears, a nose, and mouth. A tongue and tooth buds grow. Eyelids cover your baby’s eyes, and by the end of the trimester, they even have fingernails.
Genitals start to grow, but it’s too early to tell by ultrasound whether you’re having a girl or a boy.

By the end of the first trimester, your baby will be about 2 ½-3 inches long.

First Trimester To-Dos

Having a baby is one of the most joyous times in many women's lives. From thinking about the day you'll bring your little one home, to picking a name and nursery colors, the excitement is intense. But you also need to take some practical steps during the first trimester, including:

Choose a doctor. Do you want an obstetrician or a midwife? Get referrals and find out what your health insurance covers.
Schedule a prenatal visit as soon as you know you’re pregnant. You’ll cover a lot of ground in the first appointment. The doctor will take a full medical history and talk to you about your lifestyle and health habits. They’ll figure out your due date. You’ll also have blood and urine tests and possibly a pelvic exam.
Continue with prenatal visits every 4 weeks. The doctor will check your weight and blood pressure, test your urine and listen to your baby’s heartbeat.
Learn what other tests and screenings you may need, such as tests to look for genetic problems with your baby.
Start taking a prenatal vitamin with at least 400 micrograms of folic acid to help your baby’s brain and spinal cord grow properly.
Ask your doctor what prescription and over-the-counter medicines you can still safely take.
Take a look at your diet and make any changes you need to make sure you and your baby get the right nutrition. Drink plenty of water.
Break bad habits like smoking and illegal drug use. Cut out alcohol and cut down on caffeine.
Keep up your workout routine, but listen to your body. You may need to change what kind of exercise you do, or ease up a little.
Research what it costs to have a baby and start making changes. Will you have to pay for child care? Will you cut back on work? Draw up a new budget that reflects the new addition.
Decide when and how you’ll share your news. You may want to wait until you’ve heard the baby’s heartbeat, or made it safely past the first trimester. It’s also smart to find out your company’s policies on maternity leave and learn your rights before you tell your boss.

Emergency Symptoms During the First Trimester

Any of these symptoms could be a sign that something is seriously wrong with your pregnancy. Don't wait for your prenatal visit to talk about it. Call your doctor right away if you experience:

Severe abdominal pain
Heavy bleeding
Severe dizziness
Rapid weight gain or too little weight gain

Health & Pregnancy Guide

Getting Pregnant
First Trimester
Second Trimester
Third Trimester
Labor and Delivery
Pregnancy Complications
All Guide Topics

1st trimester of pregnancy: what happens to the fetus

1st trimester of pregnancy: what happens to the fetus - Private maternity hospital Ekaterininskaya Clinics

1st trimester: 1st-12th weeks

The gestational age is calculated from the first day of the last menstruation, since it is difficult to determine the exact day of conception. Since conception usually occurs in the middle of the menstrual cycle, you are not actually pregnant during the first two weeks, but this period is counted as the beginning of pregnancy.

As soon as the fertilization of the egg takes place around the 3rd week, the hormones begin to produce changes in your body little by little. As a result, you may experience some of the following symptoms:

Morning sickness. As a result of rising levels of hormones characteristic of pregnancy, up to 80% of women in the 1st trimester experience morning sickness with symptoms such as nausea and vomiting. The idea that such malaise is observed only in the morning is a common misconception. In fact, symptoms can appear at any time of the day or night. Up to 1 in 5 women experience morning sickness in the 2nd trimester of pregnancy and can sometimes persist throughout pregnancy.
If you experience morning sickness, avoid foods that make you sick, eat little and often, avoid fatty and spicy foods, drink more water. If you experience severe symptoms or symptoms that bother you, see your doctor.
Breast changes. The mammary glands will begin to increase in size, soreness may appear. The nipples will increase in size, become darker and more protruding.
Fatigue. High levels of the hormone progesterone can make you feel tired and sleepy. Rest as often as possible in a horizontal position with your legs up and eat as well as possible, which is not easy if you are experiencing morning sickness!
Increased emotionality. A higher level of emotionality, manifested as a result of an increase in hormone levels, is normal. Understanding and patience on the part of your partner and loved ones is very important here.
Food likes and dislikes. You may find yourself intolerant of one food and addicted to another. This is usually not a problem, unless you feel like eating weird foods like chalk. If you are concerned about the situation, contact your doctor.
Frequent urination. As your fluid levels increase and your uterus puts pressure on your bladder, you will become more likely to visit the toilet. Go to the toilet as soon as you feel the need - this minimizes the pressure on the bladder.
Feeling of dizziness. Sometimes you may feel a little dizzy (this is due to hormonal changes). Try not to stay on your feet for a long time and slowly rise from a sitting or lying position. If you experience severe dizziness, contact your doctor immediately.
Heartburn and constipation. Your digestive system will slow down to give you more time to digest your food. This can lead to heartburn and constipation. To help manage heartburn, try to eat small meals at regular intervals and avoid fried or spicy foods and carbonated drinks. Constipation is helped by eating a diet rich in fiber, maintaining physical activity and drinking plenty of water.

1st trimester milestones

Approximately 7 days after fertilization, the embryo implants in the uterine wall. The placenta, umbilical cord and amniotic sac will begin to form to provide nourishment and protection to the embryo.
By the end of the first 12 weeks of pregnancy, the uterus is palpable through the wall of the abdomen, the abdomen will begin to grow.

Child development in the 1st trimester of pregnancy

By the end of the 1st trimester:

All the main organs of the baby are formed, the circulatory system works.
The development of the sexual organs has begun.
Fingers are formed on the hands and feet, nails have appeared.
Facial features have formed.
The length of the baby's body is about 6 cm from the head to the lower part of the body, he is already recognizable. The baby moves in the amniotic sac, but you don't feel it move yet.

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First pregnancy, what you need to know?

The first pregnancy in a woman's life is always an important event. Information about what to expect during this period is very easy to find. But often the sources of information are not trustworthy and offer conflicting information.

Things a expectant mother needs to know

Pregnancy normally lasts 40-42 weeks and ends in vaginal delivery or caesarean section. This period will be divided into trimesters, the first - to 13 weeks inclusive, the second - from 14 to 27 weeks, and the third - from 28 weeks to delivery. Each trimester has its own characteristics.

The first trimester is the most unpredictable. It can pass very easily - some women do not even notice their condition. But in the first trimester, side effects of a sharp hormonal change in the body are also possible. Morning sickness, sudden bouts of weakness, low blood pressure, irritability, increased reaction to smells - all this happens due to the fact that the hormonal background changes dramatically in the body. All of these symptoms in the first trimester are normal, but they should be told to the attending physician.

In the first trimester, the laying and formation of the fetal body takes place. Most congenital pathologies are the result of violations during this period. In order not to provoke developmental anomalies, the expectant mother should avoid pathogens. Alcohol, nicotine, a range of drugs, and toxins in the water and air can adversely affect the health of the unborn child. You should also carefully approach the choice of cosmetics and hair products.

Pregnancy: first week

A woman can assume that the first week of pregnancy has begun only if she carefully prepared for the process of conception, calculated the time of ovulation, and chose the time for sexual intercourse. But even in this case, there can be no 100% certainty. For the first two or three weeks, a woman cannot independently determine whether pregnancy has occurred or not. Even if the fertilization of the egg has occurred, and the rapid process of embryo development has begun, it is still so small that it is not felt in the mother's body.

However, from the first days you can switch to a lifestyle suitable for pregnant women. It is recommended to avoid harmful foods, strong drugs, alcohol, smoking, stress; engage in gentle sports, walk in the fresh air.

In the second trimester, the fetus is almost formed and grows rapidly. At about 4.5 - 5 months, a woman begins to feel the movement of the child. At the same time, the belly appears and begins to grow. The baby acquires the ability to hear sounds, and if the mother or father is talking to him, he can move in response. The second trimester proceeds with a minimum number of complications, this is the best period for official preparation for childbirth: choosing a clinic, paperwork, settling issues with work, and so on. By the end of the second trimester, you should pack a bag for the maternity hospital, and in addition, sign up for a course for new mothers. In such courses, women are taught not only the correct behavior in childbirth, but also the handling of a newborn baby.

In the third trimester, the fetus is already formed, even with the onset of premature birth, the child can be saved. However, normal gestation up to 40-42 weeks is the best option. Due to the large and heavy belly, the expectant mother experiences inconvenience: her back may hurt, her legs may swell, and during sleep, a woman cannot calmly change her position.