4 Weeks Pregnant: Symptoms & What To Expect

Your pregnancy is an exciting time full of new experiences.

Learning what is happening in your and your baby’s body can help you take better care of yourself and know what to expect weekly. 

During week four, your pregnancy is moving full steam ahead.

Let’s recap the first three weeks, learn what to expect for the next seven days, and talk through early pregnancy symptoms.

Three Week Recap

At four weeks pregnant, your body has only just become pregnant. Pregnancy calculation begins on the first day of your last menstrual period (LMP).

That means that the first two weeks of your pregnancy include the first day of your last period, the week after your period (the follicular phase), and the third week after your period (when an egg is released and fertilized). 

By the fourth week of your menstrual cycle, you are officially pregnant with a fertilized egg implanted into the lining of your uterus. 

How Much Time Is Left?

You have 36 weeks left for a full-term pregnancy and are four weeks into your first trimester.

If you do the math, that means that you are actually considered pregnant for 40 weeks, or roughly ten months, not nine like is commonly accepted.

The Four Week Pregnancy Test

It can be hard to pinpoint pregnancy symptoms during the earliest weeks of the first trimester, especially since your fertilized egg has just implanted.

However, one of the biggest indications of pregnancy is a positive pregnancy test

Pregnancy tests rely on the pregnancy hormone human chorionic gonadotropin or hCG to detect a pregnancy.

The fertilized egg begins releasing this hormone within six to 12 days of uterine implantation. It may take a few days to register on a home pregnancy test

What Happens During Week Four of Pregnancy?

Even though your baby is a small ball of cells, a lot is going on to prepare for your baby’s development. 

Your Uterus at Week Four

Inside your uterus, the placenta and embryonic sac have begun to form.

The placenta is an organ that grows inside your uterus to support your baby.

It supplies the baby with oxygen and nutrients by attaching to the baby through the umbilical cord.

The placenta usually takes up residency on the side or top of your uterus. 

The embryonic sac and yolk sac form around your baby, encasing and protecting fetal development throughout the remainder of your pregnancy. 

Your Baby at Week Four

Your little one is still tiny, but you might be able to spot the gestational sac on an ultrasound.

Typically, you won’t have an ultrasound this early (that happens around week six).

Your little embryo has developed three distinct layers of cells:

  1. Endoderm. This layer of cells will become the baby’s lungs, digestive tract, and liver.
  2. Mesoderm. The middle layer of cells will eventually become your baby’s heart, a portion of the lungs, sex organs, bones, muscles, and kidneys.
  3. Ectoderm. The outer layer of cells will become your baby’s outer layer of skin, hair, and eyes and develop into their nervous system.

What Are Some Week Four Pregnancy Symptoms?

Many pregnant people don’t experience symptoms this early, but for some, pregnancy symptoms can begin as soon as implantation occurs. 

Implantation Bleeding

During the third week of your pregnancy, a fertilized egg will implant into the wall of your uterus. 

Implantation can result in mild bleeding or spotting called “ implantation bleeding.” Depending on when your egg was fertilized and implanted, you could experience implantation bleeding during the fourth week of your pregnancy.

Typically, implantation bleeding lasts only 24 to 48 hours, is not heavy, and is bright red to brown in appearance. Not everyone will experience implantation bleeding, but it is normal if you do. 

4 weeks pregnant symptoms

Metallic Taste

Early in your pregnancy, hormones begin to change rapidly.

Estrogen levels start to rise, which can do more than just give you mood swings.

Dysgeusia, a condition that causes you to perceive tastes as metallic or bitter, can happen due to a hormonal shift. 

If you find that you have a metallic taste in your mouth, don’t panic. It won’t hurt your baby and should go away within a few weeks.

In the meantime, you can try eating bland foods and avoiding ones that cause you to experience a worsening metallic taste.

Breast Tenderness and Swelling

Sore breasts can be one of the first signs of pregnancy.

If you routinely experience breast swelling and tenderness near your period, you’re more likely to experience this pregnancy symptom

Breast tenderness can begin as early as week four and continue throughout the second trimester. What’s causing the pain? 

It’s once again your hormones. As your body floods with hormones, your breasts will also begin to change to prepare to feed your baby, whether or not you choose to breastfeed. 

Increased blood flow to your breasts can cause them to swell, and your milk ducts will begin to grow to hold milk. Both can result in larger, heavier-feeling breasts that are sore to the touch. 

Heightened Sense of Smell

Suddenly you can smell a cigarette from a mile away, and even your body odor seems more pungent than usual.

A heightened sense of smell is another symptom you might experience early in pregnancy that can last until you have your baby. 

You may also experience a change in the things appealing to your nose.

For instance, certain fragrances may no longer smell the same, and some scents you usually love could lose their ability to smell good to your nostrils. 

Don’t worry; your sense of smell will return to normal once your baby arrives. 


It’s one thing to feel tired; it’s quite another to wake up from a good night of sleep and still feel like you can’t wake up.

Almost every newly pregnant person experiences fatigue in the early stages of pregnancy

The business of building a new life, and a safe and proper home in which the new life can grow, is a tall order.

Your body is focusing on this new task, which doesn’t leave a lot of energy reserves for much else. 

The good news is that fatigue usually tapers off as you enter the second trimester and doesn’t return until just before you have your baby. 

Morning Sickness

At four weeks pregnant, it’s usually a little early to experience full-fledged morning sickness (though by week six, you could be in full swing).

Some people, however, may feel nauseous, suffer from headaches, and notice a reduced appetite at four weeks. 

It’s worth noting that morning sickness doesn’t always happen in the morning.

Some pregnant people may experience morning sickness around the clock, in the afternoon, or only in the evenings. 

Additionally, vomiting and other unpleasant gastrointestinal issues, like constipation and gas, can accompany early pregnancy.

An increase in the hormone progesterone helps to relax your muscles and tendons and prepare you for childbirth. This muscle-relaxing effect also causes the intestines to relax, causing your digestive system to work more slowly. 


You just finished your period and are already feeling those tell-tale PMS-like symptoms again, but it’s too early.

This could be an early sign of pregnancy. The influx of hormones in your body can take you on a roller coaster ride of emotions. 

You’ll likely feel more emotionally charged than when you have PMS. Moodiness is entirely normal and will be a somewhat constant symptom throughout your pregnancy

You may find you are more irritable, experience more periods of happiness or sadness, or cry at the drop of a hat. It’s all a part of your body setting up shop for your healthy baby. 

Frequent Urination

Blame this one on the baby. The egg begins to release the hCG hormone once it has implanted, around week four of your pregnancy.

This hormone stimulates blood flow to your kidneys, triggering the need to urinate more. 

The reason? Your kidneys will soon filter your waste and your baby’s. That means they need to be ready to work overtime, so you’ll be in the restroom more than you usually are. 


Even though you seem to be heading to the bathroom every five minutes, you still find it hard to put on your pants.

Feeling bloated this early in pregnancy isn’t usually due to water retention, but to the hormone progesterone. 

Remember that progesterone relaxes the muscles in your body to help you prepare for childbirth, including the muscles of your digestive system. 

When the muscles of your intestines are relaxed, it can take longer for waste to exit your body. The longer it takes, the more gas, bloating, and cramping you’ll feel

Missed Period

Although you might not yet be due for your period, this is one of the most common early pregnancy symptoms.

If you don’t keep track of your period but suspect you are late, it’s worth grabbing a test to get confirmation. 

Never used one before? That’s okay. We’ve got an easy how-to guide to walk you through the process, step by step. 

How Can I Thrive During Week Four of Pregnancy?

It’s still early, but there are things you can do to help support your body and your baby during week four of your pregnancy

Confirm You Are Pregnant

If you haven’t taken a pregnancy test yet, get one and take it.

If it’s negative, but you still think you may be pregnant, it could mean the egg has not yet released enough hCG to be detectable.

In this case, treat your body as though you are pregnant and wait another week to take a test

Start Prenatal Vitamins

Now is the time to start if you aren’t already taking a prenatal vitamin.

Prenatal vitamins contain additional vitamins your body and your baby need for healthy growth and development. Especially crucial during the early stages are:

  • Vitamin D. Vitamin D supports calcium absorption. You’ll need to ensure your body gets plenty of calcium to support new bone growth. 
  • Vitamin C. Vitamin C supports healthy collagen function. Collagen is a key component of ligaments and tissues and essential to building a healthy baby. 
  • DHA. One of the omega-3 fatty acids, DHA, supports healthy brain and eye development in your baby, which happens during the first trimester and the earliest weeks of pregnancy. Ask your doctor if your prenatal vitamin contains enough.
  • Folic Acid. Folic acid is an important supplement as it can support a healthy baby through brain and spinal development. 

Find a Doctor

If you don’t already have an OB/GYN, get one! Even if you aren’t pregnant, they can help you prepare your body for a healthy pregnancy, address fertility or conception concerns, and calculate your due date when you become pregnant. 

Your health care provider will become your primary source of prenatal education and care, so it’s important to establish a good relationship with them early on. 

Have a Happy Pregnancy

Pregnancy can be full of emotions and changes, and you can prepare for the ride by keeping open communication with your doctor and ensuring you know what to expect each week of your pregnancy. 

References, Studies and Sources:

Week By Week: 4 Weeks Pregnant | American Pregnancy

Implantation bleeding: Common in early pregnancy? – Mayo Clinic 

Dysgeusia: Definition, Treatment & Causes | My Cleveland Clinic.org