First Trimester Pregnancy Symptoms

Pregnancy lasts for about 280 days or 40 weeks, starting from the first day of your last period. The 40 weeks are grouped into three trimesters. Continue reading if you want to find out what's happening with you and your baby in the first trimester (week 1-week 12) and all about pregnancy.

What is first trimester?

The first trimester begins on the first day of your last period and lasts until the end of week 12. During the first trimester, a woman's body undergoes various dramatic changes. These hormonal changes affect almost every organ system in the body and can cause pregnancy symptoms even in the first weeks of pregnancy. There's a lot going on inside your body as your baby begins to develop. Read on to find out what to expect during the 1st trimester.

Month one of pregnancy

During the first month of pregnancy, the amniotic sag forms around the fertilized egg and it helps cushion the growing embryo. The placenta is a round organ that transfers nutrients from the mother to the baby and develops in the first trimester of pregnancy. The eyes, mouth, lower jaw, and throat of the baby are slowly developing. Blood cells are taking shape and circulation will soon begin. By the end of month one, your baby will be around 6-7mm long.

Month two of pregnancy

The baby's facial features continue to develop and fingers, toes, eyes, ears, arms and legs are forming in the second month of pregnancy. The brain is also well-formed, the digestive tract and sensory organs begin to develop and bone replaces cartilage. In month two the embryo starts to move, even though the mother cannot feel it yet. By the end of the second month, the fetus is about 2.54cm long and weighs around 9.45g.

Month three of pregnancy

In month three of pregnancy, your baby is fully formed and already has arms, fingers, hands, feet, and toes. The baby can open and close its mouth and fists. Fingernails and toenails are starting to develop and the reproductive organs are also developed. By the end of the third month, your baby is about 7.6-10 cm long and weighs around 28g. However, the baby's gender still can't be distinguished on ultrasound.

Your baby's most critical development has taken place during the first trimester, so your chances of miscarriage are significantly lower after three months.

How long is the first trimester?

The first trimester lasts from week 1 through the end of week 13 of pregnancy.

What are the common first trimester symptoms?

Even though you may not look pregnant yet, you're probably feeling it. That's because the pregnancy hormones are preparing your body for the baby for the next nine months.

Your period stopping is a clear sign that you are pregnant. However, you might experience some other pregnancy symptoms like fatigue, nausea, bloating, tender breasts, cravings, distaste for certain foods, headache, mood swings, constipation, backache, heartburn and need to pass urine more often. These temporary discomforts are only part of the amazing process that's happening inside your body and will go away as the pregnancy progresses. Take a look at some of the most common first trimester pregnancy symptoms:

Morning sickness

Morning sickness is one of the most common first trimester symptoms. This unpleasant symptom appears in the week 5 and it doesn't just strike in the morning. Even though it's called morning sickness, it can affect women at any time of the day or night. With morning sickness, some pregnant women have a feeling of sickness (nausea) and vomit.

Hormonal changes are probably the cause of morning sickness. If you have nausea, try drinking ginger tea, plenty of fluids, and also get plenty of rest. Eat small but frequent meals that are high in carbohydrate and low in fat. If you have severe morning sickness, your doctor might recommend some medication.

Mood swings

Mood swings during pregnancy are also common. Pregnancy is an exciting experience full of physical and emotional changes, so you may have some worries that contribute to your mood swings. During the first trimester, you may feel up, then down, then up again. Mood changes can be caused by physical stress, fatigue, or by the increased levels of hormones estrogen and progesterone. Hormonal changes affect your level of neurotransmitters, the brain chemicals that regulate mood. Mood changes are mostly experienced between 6 to 10 weeks and then again in the third trimester. So, try to relax and get plenty of sleep. Eat well, get regular physical activity, and try pregnancy yoga class or meditation.

Tender breasts

Sensitive and swollen breasts are one of the earliest 1st trimester symptoms. The tenderness is noticeable from week 3 or 4 - before you even know you're pregnant. Your breasts may become very tender and sore, but this unpleasant symptom will disappear after the first trimester of pregnancy. Tender breasts are also caused by the increased levels of hormones estrogen and progesterone. It might be uncomfortable, but these dramatic changes are important because they are preparing your breasts for the role of feeding your baby. The best thing you can do is to buy a well-fitting, supportive bra to ease the soreness and avoid underwired bras because they can be really uncomfortable.


Constipation is probably one of the most unpleasant of all pregnancy symptoms during the first trimester. The increase in the hormone progesterone relaxes smooth muscles as well as the digestive tract. This results in slow movement of food through the digestive tract also known as constipation. If you're experiencing constipation, eat foods rich in fiber such as brown rice, beans, whole-grain bread, fresh fruits, and vegetables. Drink plenty of water and exercise regularly. Constipation is usually not serious, but if you have severe constipation accompanied by abdominal pain, call your doctor immediately.


Headaches are quite normal, especially in 1st trimester of pregnancy. Headaches won't affect your baby, but they could be related to something in your lifestyle. Stress, a strenuous exercise or a particular food may the cause of your headache. Skipping meals and not drinking enough can also cause tension headaches in pregnancy. Headaches tend to disappear completely by the end of the first trimester.


Cramping in first trimester is often the result of the normal hormonal changes that occur during your baby's development. Cramps during first trimester are described as pulling sensations on one or both sides of the abdomen. This symptom accompanies many pregnancies and in most cases, it's just a normal part of the pregnancy. Cramping during first trimester occurs when the uterus expands and it may be more painful when you sneeze, cough, or change positions.

If you're experiencing first trimester cramping, simply soak in a warm bath or place a hot water bottle wrapped in a towel on the aching area. Also, make sure you get plenty of fluids. Sometimes, first trimester cramps can be caused by ectopic pregnancy, miscarriage, or preeclampsia. So, call your doctor if you're experiencing severe pain that does not go away, vaginal cramping, bleeding, discharge, dizziness, and cramping along with pain in the neck and shoulders.

First trimester prenatal check-up and screening

As soon as you confirm your pregnancy you need to schedule your first prenatal appointment. Your health care provider will check your weight and height in order to calculate your BMI and will determine the recommended weight gain for a healthy pregnancy. He/she will measure your blood pressure, breathing rate and heart rate and will do a complete physical exam.

Your health care provider will also examine your vagina and the opening of your cervix. Changes in the cervix can help confirm the stage of your pregnancy. Blood tests might be done to check your blood type and check immunity to infections.

Your doctor might offer ultrasound and other screening tests to detect fetal abnormalities. First trimester screening is a prenatal test that is very important because it offers information about the baby's risk of chromosomal conditions. Usually, first trimester screening is done between weeks 11 and 14 of pregnancy. Using the results of the blood test and the ultrasound, your doctor will be able to determine your chances of having a baby with Down syndrome or trisomy 18.