5 Weeks Pregnant: Symptoms, Baby Development and What to Expect

At 5 weeks pregnant, symptoms such as nausea, sore breasts, fatigue and frequent urination often begin as pregnancy hormones climb, while an embryo about the size of a sesame seed starts forming its brain, spinal cord and heart.

If last week was about a test result, this week is about how you feel. For many people, 5 weeks pregnant is when the first real symptoms show up and the questions start.

This guide gives the most space to symptoms and what helps. Each figure is attributed to its medical source, and where sources differ we print both.

5 Weeks Pregnant at a Glance

How the weeks are counted. Weeks are counted from the first day of your last menstrual period (LMP). Mayo Clinic spells it out: the fifth week of pregnancy is the third week after conception. That assumes a typical 28 day cycle, and an early ultrasound can change the dating: Mayo Clinic says that if the two due dates differ by more than seven days, the ultrasound is typically used.

Your Baby’s Development at 5 Weeks

MedlinePlus, from the National Institutes of Health (NIH), marks week 5 as the start of the embryonic period. The brain, spinal cord and heart begin to develop, the gastrointestinal tract starts to form, and cells take on specific jobs, such as blood, kidney and nerve cells.

Mayo Clinic describes the embryo as three layers: the ectoderm, the outer layer, which gives rise to the nervous system; the mesoderm, where the heart and circulatory system form; and the endoderm, where the lungs and intestines develop.

The neural tube, and why folic acid matters now. Cleveland Clinic says the neural tube, which becomes the brain and spinal cord, forms in week 5. Mayo Clinic describes it closing in week 6. This is the window folic acid is meant for: the Centers for Disease Control and Prevention (CDC) says neural tube defects are major birth defects of the brain and spine that happen in the first few weeks of pregnancy, often before you know you are pregnant.

The heart. Sources differ. Nemours KidsHealth describes a bulge that will develop into the heart. Cleveland Clinic says the tiny heart tube will pulse 110 times a minute by the end of the fifth week. Mayo Clinic places the heart starting to form in week 6. MedlinePlus says that in weeks 6 to 7 the heart beats at a regular rhythm, which can be seen by vaginal ultrasound. So early cardiac activity may be starting, but a scan generally does not show it at 5 weeks.

How Big Is Your Baby at 5 Weeks?

Nemours KidsHealth says that at 5 weeks your baby is about the size of a sesame seed and weighs very little. It gives no number, and neither does Mayo Clinic or MedlinePlus. The nearest measurement on the pages we read is Cleveland Clinic’s: about 2 millimeters at the end of week 4, the size of a poppy seed.

StatPearls, an NIH clinical reference, notes that the embryo itself becomes visible on ultrasound in the sixth week, so there is typically nothing to measure yet. Mayo Clinic’s first figure comes at week 8: about 1/2 inch (11 to 14 millimeters) from the top of the head to the bottom of the tailbone.

5 Weeks Pregnant Symptoms

Nemours KidsHealth says breast tenderness, bloating, mood swings and fatigue can start this week. Mayo Clinic’s first trimester guide explains why each symptom happens and what helps.

• Nausea and vomiting: Mayo Clinic says morning sickness often begins between 4 and 9 weeks, can strike at any time of day and is tied to rising hormone levels. What helps, per Mayo Clinic: small, frequent meals; bland, low-fat foods such as bananas, rice, applesauce and toast; foods that contain ginger; avoiding smells that set you off; and sipping cold, clear fluids.
• Fatigue: Mayo Clinic links early pregnancy tiredness to rising progesterone. Its advice: rest as much as you can and take a 15-minute nap if possible.
• Tender, swollen breasts: hormonal changes can make your breasts sensitive or sore. Mayo Clinic says the discomfort will likely ease after a few weeks as your body adjusts.
• Peeing more often: Mayo Clinic explains that the amount of blood in your body increases, so the kidneys process extra fluid that ends up in the bladder.
• Food aversions and a sharper sense of smell: Mayo Clinic says your sense of taste may change and smells may seem stronger. Open a window while cooking.
• Bloating, constipation and heartburn: Mayo Clinic says high progesterone can slow the movement of food, and that pregnancy hormones relax the valve between the stomach and esophagus. Fiber, fluids and activity help with constipation; for heartburn, eat small meals and do not lie down right after eating.
• Mood swings: Mayo Clinic says you may feel delighted, anxious, excited and exhausted, sometimes all at once. See your health care professional if mood changes become serious or intense, or you feel sad or overwhelmed for longer than two weeks.
• Mild cramping and light spotting: Nemours says you may have slight cramping and spotting, which some people mistake for a period. MedlinePlus defines spotting as a few drops of blood now and then, not enough to cover a panty liner, and bleeding as a heavier flow that needs a pad. It lists implantation, sex, infection and hormone changes among first trimester causes, and also miscarriage and ectopic pregnancy, so tell your provider about any bleeding.

No symptoms at 5 weeks? That happens too. Mayo Clinic’s 4 to 9 week range means nausea may not have started, and Nemours describes this week’s symptoms as ones that can start now, not ones everyone has. If you are worried, call your provider.

Nausea: when to worry. MedlinePlus describes hyperemesis gravidarum as extreme, persistent nausea and vomiting that can lead to dehydration, weight loss and electrolyte imbalances, typically beginning between 4 and 8 weeks. Contact your provider if you have signs of dehydration (dark urine, weakness, lightheadedness), cannot keep fluids down for more than 12 hours, see blood in your vomit, have abdominal pain, or lose more than 5 pounds.

Your Body and Belly at 5 Weeks

A 5 weeks pregnant belly looks like your usual belly. With an embryo the size of a sesame seed, nothing shows from the outside, though you may feel bloated. See pregnant belly by month for when a bump usually appears.

The bigger changes are hormonal. Mayo Clinic says that in the fifth week hCG rises quickly, and that higher levels of estrogen and progesterone stop the menstrual period and fuel the growth of the placenta. Nemours says a home test could probably detect your pregnancy this week, so retest if you got a negative at 4 weeks pregnant. Our hCG levels guide has the ranges.

Prenatal Care, Tests and Appointments Around Week 5

What a 5 weeks pregnant ultrasound can show. Most people do not have a scan this early. If you do, expect very little on the screen. StatPearls gives these typical timings, in weeks of pregnancy:

So at 5 weeks, a sac and perhaps a yolk sac, with no embryo or cardiac activity yet, can simply reflect how early it is. Your provider will tell you whether they want to look again.

The first prenatal visit. Mayo Clinic says to make your first prenatal appointment when you find out you are pregnant, so call now if you have not. Expect a medical history that covers every medicine and supplement you take, a due date, a physical exam, and blood tests for blood type and Rh status, hemoglobin, immunity to rubella and chickenpox, and infections including hepatitis B, syphilis and HIV. After that, visits are often about every four weeks in the first trimester.

What to Do This Week: A Simple Checklist

• Keep taking folic acid: the CDC says all women capable of becoming pregnant should get 400 micrograms (mcg) of folic acid daily, before and during early pregnancy, to help prevent neural tube defects.
• Book the first prenatal visit: ask what to do until then if you have a health condition or take regular medicine.
• Build a nausea plan: keep plain snacks within reach, eat small amounts often, and sip fluids through the day.
• Keep alcohol and tobacco out: Mayo Clinic notes your provider will ask about both. The CDC’s wording on alcohol is in our 4 weeks pregnant guide.
• Start a question list: bring it to the first visit, along with the first day of your last period.
• Rest when you can: fatigue is common this week.

Sleep at 5 Weeks Pregnant

Week 5 can bring more tiredness and more broken nights. MedlinePlus says you may need more sleep than usual in the first trimester, and explains the extra bathroom trips: your kidneys are filtering the extra blood your body is making, which means more urine.

• If you are up to pee: MedlinePlus suggests not drinking large amounts within a few hours of bedtime.
• If nausea hits at night: MedlinePlus suggests a few crackers before bed.
• If you are exhausted by afternoon: MedlinePlus recommends short daytime naps.
• If you cannot wind down: keep a steady bedtime and wake time and cut back on caffeine, per MedlinePlus.

Sleep position. MedlinePlus advises trying to sleep on your side with your knees bent and says it is best not to sleep flat on your back. It does not tie that advice to a specific week, so ask your provider when it applies to you. To get used to side sleeping, try a pregnancy pillow.

Sleep aids. MedlinePlus says not to take any sleep aids in pregnancy, including over the counter medicines and herbal products. See can you take melatonin while pregnant.

For Partners: How to Help at 5 Weeks

• Take over cooking, or at least the smells that turn her stomach.
• Keep plain snacks and cold water stocked, and protect naps and early nights.
• Know the warning signs below, so you can make the call or drive if she needs care.
• Small comforts count. Our gifts for pregnant women list has ideas.

Looking Ahead: What Comes Next

• Week 6: Mayo Clinic says the neural tube is closing and small buds appear that will become arms. Weeks 6 to 7 are also when an ultrasound typically first shows cardiac activity (StatPearls).
• The whole trimester: our first trimester guide runs through 13 weeks pregnant. To share the news, see pregnancy announcement ideas.

Related Betteroo Guides

• 4 weeks pregnant
• First trimester guide
• hCG levels by week
• 13 weeks pregnant
• Can you take melatonin while pregnant?
• Pregnant belly by month

When to Call Your Provider

Call whenever you are worried. You do not have to wait for the first appointment.

Call 911 or go to the nearest emergency room for signs of ectopic pregnancy. Mayo Clinic says the first warning signs are often light vaginal bleeding and pelvic pain, and to seek emergency help for:

• Severe abdominal or pelvic pain accompanied by vaginal bleeding.
• Extreme lightheadedness or fainting.
• Shoulder pain.

Contact your provider right away if, as MedlinePlus lists, you have heavy bleeding, bleeding with pain or cramping, dizziness and bleeding, or pain in your belly or pelvis. If you cannot reach your provider, go to the emergency room. Also call if you cannot keep fluids down for more than 12 hours or see blood in your vomit.

Seek medical care right away for any of the CDC’s urgent maternal warning signs, and say that you are pregnant. They include:

• Vaginal bleeding or fluid leaking during pregnancy.
• Severe belly pain that doesn’t go away.
• Severe nausea and throwing up.
• Dizziness or fainting.
• Fever of 100.4 F or higher.
• A headache that won’t go away, or changes in your vision.
• Trouble breathing, chest pain or a fast-beating heart.
• Thoughts about harming yourself or your baby.

If something just doesn’t feel right, the CDC says to talk to your health care provider. This article is general education, not medical advice.

Frequently Asked Questions