What to Expect When 4 Weeks Pregnant

Discovering you’re pregnant can be one of the most exciting times in your life. At 4 weeks pregnant, you’re at the very beginning of an incredible journey. Even though you may not be showing yet or feeling any major symptoms, your body is going through huge changes as it prepares to nurture a growing baby.

This article will walk you through exactly what to expect during your fourth week of pregnancy. From common early symptoms to crucial developmental milestones, you’ll learn all about this special stage and how to take care of yourself and your tiny bundle of joy.

Key Takeaways When 4 Weeks Pregnant

  • Your period will likely be late or missed entirely, which is often the first clue you’re pregnant. Take a pregnancy test to confirm.
  • Hormones like hCG and progesterone are ramping up rapidly, which can cause breast tenderness, mood swings, fatigue, and more.
  • Morning sickness may start to appear around 4 weeks for some women. Drink plenty of fluids and eat small, frequent meals.
  • Your baby is a ball of cells called a blastocyst that has implanted in your uterus lining. Significant development of vital organs is happening.
  • Make your first prenatal doctor’s visit to confirm the pregnancy, discuss any medications, and learn about nutrition and lifestyle adjustments.
  • Avoid smoking, alcohol, certain foods, cat litter, and anything else that could jeopardize your baby’s health.
  • Stay hydrated, exercise moderately, eat a balanced diet, reduce stress, and get plenty of rest.

Common Symptoms to Expect at 4 Weeks Pregnant

One of the very first signs many women notice is a missed menstrual period. Although cycles can occasionally be irregular, a missed period is often the telltale clue that leads women to take a pregnancy test. The levels of the pregnancy hormone hCG will be high enough around 4 weeks pregnant to show up positive on a home test.

Some other early pregnancy symptoms that may appear around your fourth week include:

  • Breast tenderness: Rising levels of hormones like estrogen and progesterone cause increased blood flow to the breasts. This can make them tender, tingly, or sore.
  • Fatigue: Fatigue is common during the first trimester as your body works overtime to support the pregnancy. Rest as much as possible.
  • Mood swings: Hormone fluctuations can trigger mood swings like irritability, anxiety, and crying spells at this stage. Be patient with yourself!
  • Bloating: Hormonal shifts slow digestion, leading to gas, bloating and constipation. Stay hydrated and eat fiber-rich foods.
  • Frequent urination: Hormones and extra fluids being processed by your kidneys cause you to urinate more often. This increases as pregnancy progresses.
  • Heartburn: Progesterone relaxes the sphincter muscle between the stomach and esophagus, allowing acidic stomach contents to flow upward.
  • Headaches: Changing hormone levels, dehydration, stress and fatigue can all contribute to headaches during early pregnancy.
  • ** Cravings/aversions:** You may notice strong cravings or aversions to certain foods due to hormones and taste/smell sensitivity. Go with whatever appeals to you!

While concerning symptoms like heavy bleeding, severe cramping, or pain should be immediately addressed with your doctor, the majority of symptoms are a normal part of early pregnancy as your body adjusts to its new role.

When Does Morning Sickness Start?

Nausea and vomiting, commonly known as morning sickness, affects over half of all pregnant women. For most, morning sickness starts between weeks 4-6. However, it can begin as early as week 3 or 4 after conception. The exact cause is unknown, but it’s likely linked to the hormone hCG as levels peak around the same time.

Morning sickness is a misnomer since it can strike any time of day. Early symptoms may include a metallic taste in the mouth, strong food aversions, an overly sensitive sense of smell, salivation, burping, and indigestion. Nausea and vomiting episodes tend to worsen over the following weeks but improve again by weeks 14-16 for most women.

To manage morning sickness:

  • Have a snack like crackers before getting out of bed. Eat small, frequent meals throughout the day.
  • Avoid triggers like strong smells and fatty, spicy foods. Stick to bland choices that appeal to you.
  • Stay hydrated by sipping cold, carbonated drinks like ginger ale or lemon-lime soda.
  • Take vitamin B6 and doxylamine tablets, which are safe anti-nausea medications doctors can prescribe.
  • Rest as much as possible. Fresh air and light exercise like walking can also help.

Seek medical attention if you cannot keep any food or fluids down for over 24 hours, are severely dehydrated, or your nausea is impacting your quality of life.

Your Baby’s Development at Week 4

At this point your baby is in the earliest stages of development as a tiny ball of cells. Here are some incredible milestones occurring around 4 weeks pregnant:


In your baby’s very first stage, fertilization occurs when sperm and egg meet in the fallopian tube to form a single cell called a zygote. This single cell begins dividing rapidly into many as it travels down the fallopian tube towards the uterus. This multi-cellular ball is now called a morula.

Within a few days, the morula becomes a blastocyst – a fluid-filled ball of around 150-200 cells consisting of 2 main cell types. The inner group of cells will become your baby, while the outer group will develop into the placenta.

Around day 6-10 after fertilization, the blastocyst arrives at the uterus and begins the implantation process. It embeds into the thickened uterine lining, where it will continue to receive oxygen and nutrients from you.

Implantation often coincides with light spotting, mild cramping, breast tenderness, and other early pregnancy symptoms.

Rapid Cell Growth

Now implanted in its new home, your baby still doesn’t actually look anything like a baby yet. The blastocyst is made of just a couple hundred cells arranged in 3 layers that will each form different body parts:

  • Ectoderm: Skin, hair, nails, tooth enamel, nervous system, eyes, inner ears
  • Mesoderm: Muscles, bones, kidneys, heart
  • Endoderm: Lungs, intestines, thyroid gland, bladder, pancreas

Though tiny, these layers represent major progress. In just a week your baby’s cells will multiply exponentially and differentiate into specialized types forming the building blocks of the placenta and your baby’s organs and body systems.

Establishing the Placenta

The placenta is an incredible temporary organ that develops during pregnancy to provide nourishment and protection for your growing baby. Around week 4, cells on the outer layer of the blastocyst begin forming the placenta and connecting it to your uterine lining via blood vessels.

This lifeline will deliver oxygen and nutrients, remove waste, and act as your baby’s endocrine system producing pregnancy hormones. The amniotic sac and fluid that cushion and protect your baby also start forming this week from the outer cell layer.

Proper placenta development is critical in early pregnancy. Issues like low hormone levels or inadequate blood flow could result in problems sustaining a healthy pregnancy.

Hormones Surge

Two key hormones—human chorionic gonadotropin (hCG) and progesterone—surge during week 4 to support your pregnancy:

HCG is produced by cells that will become the placenta. It signals to your ovaries to maintain production of estrogen and progesterone to sustain the pregnancy. HCG levels double every 48-72 hours in early pregnancy.

Progesterone helps build and maintain the uterine lining that nourishes the embryo. It relaxes smooth muscle tissue allowing the uterus and fallopian tubes to accommodate the growing baby.

These hormones are responsible for many of the common physical symptoms you may notice in your 4th week of pregnancy. They will continue rising steadily for the coming weeks.

Lifestyle Tips for a Healthy Pregnancy

Now that you are nourishing a growing baby, it’s important to make smart lifestyle adjustments to give your little one the best start right from the beginning. Here are some tips for a healthy pregnancy during your fourth week and beyond:

Start Taking Prenatal Vitamins

Prenatal vitamins provide extra folic acid and iron which are crucial for your baby’s brain, spine, and blood cell development in these early weeks. Ask your doctor for a prescription prenatal. Over the counter varieties may not have the right amounts of nutrients you need.

Boost Your Folic Acid Intake

In addition to a prenatal vitamin, make sure you’re getting at least 600 mcg of folic acid each day from your diet or supplements. Good sources include fortified breads and cereals, dark leafy greens, beans, citrus fruits, and nuts. Ramping up folic acid intake early helps dramatically lower risk of neural tube defects.

Exercise Moderately

Light exercise like walking, swimming, or prenatal yoga is great for staying active in a way that feels comfortable during your fourth week. Avoid bumpy exercises, contact sports, or anything too strenuous as your body adjusts to pregnancy.

Stay Hydrated

Aim for 10-12 cups of fluids daily while pregnant. Water is best, plus milk, fruit juice, smoothies, decaf tea/coffee, and broth counts too. Proper hydration will help ease symptoms like headaches, constipation, fatigue, and lightheadedness.

Get Plenty of Rest

Growing a baby is hard work! Don’t feel guilty indulging in daytime naps or earlier bedtimes. Prioritize sleep, especially in your first trimester. Say no to extra tasks that can wait. Restorative rest ensures you and baby stay happy and healthy.

Monitor Caffeine Intake

Limit caffeine from coffee, sodas, tea, and chocolate to 200 mg or less per day. High amounts have been linked to increased miscarriage risk and low birth weight.

Eat Nutritious Foods

Focus your diet on plenty of fruits/veggies, lean proteins, whole grains, dairy, nuts, eggs, beans, and healthy fats from plant oils, avocados, etc. Eat until satisfied and continue gaining weight gradually as recommended by your doctor.

Be Selective About Seafood

Seafood containing vital nutrients like omega-3s should be included in your pregnancy diet. However, limit high mercury types like swordfish, mackerel, shark to no more than 1 serving a week. Avoid raw shellfish to steer clear of bacteria.

Steer Clear of Risky Substances

Completely avoid smoking, secondhand smoke, alcohol, recreational drugs, and unnecessary medications while pregnant. Even small amounts of these substances can negatively impact your baby in these critical developmental stages.

Make Time to De-Stress

Carving out time for yourself each day to relax is a must. Try calming practices like prenatal massage, meditation, journaling, deep breathing, aromatherapy, or soaking in the tub. Keeping stress hormones in check will help you and baby stay balanced.

Doctor Appointments and Tests

One of the most important steps during your fourth week is scheduling your first prenatal checkup. This initial visit will likely include:

  • Confirming your pregnancy: Either through a urine test or bloodwork measuring hCG levels.
  • Calculating your due date: Determined from the start date of your last period. You’ll get a general estimation that can be adjusted later on after your first ultrasound.
  • Discussing your health history: Your doctor will ask questions about your periods, previous pregnancies, medical conditions, medications, supplements, family history, etc. to assess any potential pregnancy risks.
  • Testing for issues: Bloodwork, cultures, and urinalysis checks for anemia, genetic abnormalities, immunity to certain diseases, UTIs, and other conditions.
  • Prescribing prenatal vitamins/folic acid: If you’re not already taking them, your doctor will provide the correct prescription strength based on your health profile.
  • Scheduling upcoming visits: You’ll need 1-2 monthly visits up to week 28, then every 2 weeks until 36 weeks, then weekly visits until delivery.

Don’t hesitate to ask your doctor any questions you have during this first visit and beyond. They are there to support you each step of the way during your pregnancy journey!

When to Call the Doctor

While most symptoms are perfectly normal in early pregnancy, contact your healthcare provider right away or go to urgent care if you experience:

  • Heavy vaginal bleeding (soaking a pad an hour)
  • Severe abdominal cramping or pelvic pain
  • Reduced hCG levels or miscarriage signs
  • Fevers over 100.4°F (38°C)
  • Persistent, severe nausea/vomiting
  • Burning or pain during urination
  • Thoughts of harming yourself or your baby

Otherwise, any concerns like mild spotting, lack of weight gain, emotional changes, breast changes, or food aversions can be addressed at your next prenatal visit. Don’t hesitate to call in if something concerns you.

Healthy Eating Tips for Your 4th Week of Pregnancy

Along with taking your prenatals, eating nutritious foods is vital for your health and your growing baby starting immediately in week 4. Here are some tips for healthy eating in early pregnancy and beyond:

Emphasize the Essentials

Load your diet with plenty of:

  • Lean protein: Beans, lentils, eggs, seafood, poultry, nuts, seeds. Boosts energy and supports baby’s cell growth.
  • Fruits/veggies: Enjoy fresh or frozen. Provides key antioxidants, fiber, vitamins, minerals. Target several servings per day.
  • Whole grains: Oats, quinoa, brown rice, whole wheat bread. Choose over processed grains to maximize nutrients.
  • Dairy: Milk, yogurt, cheese, calcium-fortified alternatives. Excellent source of calcium to support bones/teeth development.
  • Healthy fats: Nuts, seeds, avocado, olive oil, salmon. Helps build baby’s skin, brain, tissues.

Snack Smart

Small, frequent snacks help combat nausea and heartburn while providing a steady stream of energy and nutrients. Some healthy pregnancy snack ideas include:

  • Fresh fruits with nut butter
  • Yogurt with granola
  • Veggies with hummus
  • Cheese and whole grain crackers
  • Trail mix with nuts and dried fruit
  • Smoothies or fruit-infused water

Stay Hydrated

Aim for around 80-100 oz of fluids per day. Water is best, plus milk, fruit juice, decaf coffee/tea, and herbal iced tea. Proper hydration prevents headaches, dizziness, and constipation.

Give in to Cravings

Pregnancy cravings are your body’s way of signaling what it currently needs nutritionally. Give yourself permission to indulge cravings for healthy foods like fruit, dairy, veggies, or lean protein.

Limit Empty Calories

Steer clear of junk foods, sweets, sodas, and fried or processed items which pack in calories without nutrients you require. These can contribute to excess weight gain.

Go Easy on Caffeine

Restrict caffeine from coffee, tea, soda, and chocolate to 200mg or less per day. Excessive amounts are linked to miscarriage and low birth weight risks.

Get Iron and Calcium

Ensure you’re getting adequate iron and calcium from foods like spinach, red meat, beans, lentils, dairy products, dark leafy greens, and calcium-fortified plant milks or orange juice. These nutrients are vital for you and baby’s developing cells.

Safe Medications When Pregnant

Certain over-the-counter medications are safe during pregnancy to help relieve unpleasant symptoms. Always check with your doctor first, but some relief options may include:

For Nausea

  • Vitamin B6/doxylamine (Unisom)
  • Ginger supplements
  • Sea bands (apply pressure to wrists)

For Heartburn

  • Tums or other antacids
  • Famotidine (Pepcid)

For Headaches

  • Acetaminophen (Tylenol)
  • Warm or cold compresses

For Constipation

  • Prune juice or Milk of Magnesia
  • Colace stool softener
  • High-fiber foods and fluids

For Congestion

  • Saline nasal spray or drops
  • Humidifier
  • Guaifenesin (Mucinex) – expectorant only, NO decongestants

For Allergies

  • Loratadine (Claritin)
  • Diphenhydramine (Benadryl) – occasional use only

Talk to your doctor before using any medication while pregnant, including herbal supplements. Never exceed dosage on any product label and avoid using anything for prolonged periods without medical approval.

Risks and Warning Signs to Watch For

While most women have uneventful pregnancies, here are some risks and warning signs to watch for around 4 weeks and beyond:

Ectopic Pregnancy

A rare condition where the fertilized egg implants outside the uterus, usually in the fallopian tube. Symptoms are abnormal bleeding/cramping with one-sided, severe abdominal pain. Treated with medication or surgery.


Loss of the pregnancy before 20 weeks gestation. Occurs in 10-25% of pregnancies, typically due to chromosome abnormalities. Warning signs are heavy bleeding with cramping and tissue passing from the vagina.

Molar Pregnancy

A rare complication where an abnormal fertilized egg forms an irregular growth in the uterus instead of a normal embryo. Requires immediate treatment and monitoring to prevent serious complications.

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