Week four pregnancy - your baby's the size of a poppyseed.

What To Expect During Week Four of Pregnancy

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Although you’ve still got months to go before your baby’s arrival, you’ve achieved your first milestone of many. At week four of pregnancy, you’ve hit the one-month mark. Only 36 weeks left! How did you get on with Week 3?

Many challenges and unfamiliar experiences are ahead as your body houses new life!

Stick with us for week-by-week updates on your baby’s development and the physical changes you’re going through. As the new guest rapidly grows and develops, we’ll answer all your questions about baby size, progress, and what’s happening inside your body. 

Here’s what to expect this week.

At a Glance: Week Four Pregnancy

  •  Week four focuses on implantation as the growing blastocyst attaches to the uterus.
  • You might be in the dark about your pregnancy, but it’s a big development week for your tiny baby.
  • It’s still early for pregnancy symptoms, although you might experience spotting, abdominal pressure and tender breasts.
  • Have pregnancy tests on standby! You could test positive this week.
  • By the end of week four, your baby will be roughly the size of a poppy seed.
  • Continue preparing your body for pregnancy by taking prenatal vitamins, fixing your diet and quitting bad habits.

Week Four Pregnancy Overview (Welcome to Your New Home, Baby!)

Week four marks significant developments for your budding baby. Already, it’s been fertilised by sperm and has successfully found its way to your uterus. Next, the ball of cells burrows through your uterus and connects to the uterine lining, where it stays for several months.

Implantation is vital at this stage because there’s no pregnancy if it doesn’t take place. It should happen soon if implantation hasn’t occurred by week three’s end.

But before implantation, the blastocyst might hang around the uterus until it’s ready to descend toward the uterine lining. Then, once firmly rooted in your warm and hospitable womb, the blastocyst prepares for a lot of crucial early development.

Soon, the blastocyst’s inner group of cells differentiate from its outer layers to form an embryo. This embryo has three cell layers that grow into different body parts and systems. 

Some outer cells are already developing into the placenta, a life-giving organ that will be fully functional by week twelve of pregnancy. Additionally, as your future baby needs nourishment at the get-go, these outer cells delve further into the uterus wall to receive nutrients for the embryo’s energy needs from the endometrium. The endometrium is the embryo’s most significant source of nutrition initially, but not the only one. The yolk sac also provides essential nutrients and gas exchange during early embryonic development.

Besides nourishment, your baby needs protection, which the gestational sac provides during the very early stages of pregnancy. The water-filled cavity contains your tiny embryo, offering it a safe environment to grow and the best start to life.

Baby Size and Latest Developments For Week Four Pregnancy

Less than 2mm long, your baby’s tiny. Comparatively, they’re proportionate with a poppy seed on a bagel or lemon-poppyseed cake.

Although barely visible to the untrained eye, your baby’s rapid development is astounding. Here’s everything that’s growing by week four.

  •  The amniotic sac begins to form around the baby. It’s still relatively small but will perform several functions throughout the pregnancy, safeguarding your baby and providing a clean and stable place to grow. The amniotic sac works in tandem with the gestational sac for a while before the latter disappears once serving its purpose. 
  • The placenta, the organ that gives food and oxygen, provides hormones to support growth and removes waste from the baby’s home, has begun growing too. 
  • A yolk sac attaches to the embryo until the placenta is functional, providing everything it needs – nutrients, gas exchange with the mother, red blood cells and early immune support.
  • The embryo now has three distinct layers of cells – called the endoderm, mesoderm, and ectoderm – which become different body parts and systems over time – skip ahead to learn the details of these developments.
  • The neural tube, from which the spine, brain and backbone grow, will emerge soon. 
  • Other exciting developments are also in the works. Your baby doesn’t have a heart yet, but blood vessels are forming that’ll eventually transform into a heart and circulation system.

Body Changes for Week Four Pregnancy

With implantation occurring, there’s no denying you’re pregnant by week four. But unless you’re showing week four pregnancy symptoms, you might not be aware that a baby’s on the way or of the changes happening behind the scenes.

But the appearance of hCG might change that now or in one or two weeks. hCG, short for human chorionic gonadotropin, is a pregnancy chemical stimulated by the tissues that develop into the placenta to maintain a pregnancy.

Starting from conception, the level of hCG doubles every 48 to 72 hours. Once hCG in your body reaches a certain amount, not only is it detectable in your urine, but it causes pregnancy-related symptoms too.

We looked into early-period symptoms in our week three guide. You might also notice these signs.

1. Implantation Spotting and Cramping

25% of pregnant people experience spotting or implantation bleeding, which occurs when the blastocyst embeds into the uterine lining. Many people don’t know about spotting and immediately worry there’s something wrong. But it’s common, temporary and the equivalent of an ultra-light period. Besides spotting, you might experience light cramping but nothing worse than that. 

2. Lower Abdominal Pressure

A tugging sensation at your lower abdomen can spell pregnancy. The sensation is a reaction to implantation and the uterine lining thickening for its new resident.

3. You’re Not Menstruating

A missed period signals that you might be pregnant, which you can confirm with a pregnancy test. Levels of hCG can be detected 12 to 14 days after conception, so you may get a positive result by week four. 

4. Fatigue

Feeling extremely tired or low on energy is expected as all your energy is redirected into building another person. Unfortunately, fatigue is a persistent symptom throughout your pregnancy, although there might be some reprieve during the second trimester. 

4. Morning Sickness

Nausea or morning sickness affects many pregnancies, characterised by nausea or nausea and vomiting. It begins early into the pregnancy and should be over by the end of the first trimester.

5. Emotional Upheaval

Ever heard expecting mothers complain about “being pregnant and hormonal?” Your emotions are out of wack thanks to a cocktail of fluctuating hormones coupled with the stress and excitement of conceiving. They’ll eventually stabilise, though. 

6. Urinating More Often

The need to urinate often is more common further along in the first trimester when your uterus puts pressure on the bladder. But frequent urination can also be a fact of life this early.

Week Four Pregnancy Tips and Tricks

You might already know you’re pregnant or waiting expectantly to find out. Even though pregnancy is tough on our emotions and body, you must be as healthy as possible as a mom-to-be. Here are a few tips to prepare you for the weeks and months ahead.

1. Catch Up on Weeks One Through Three

If your pregnancy news has been a surprise, read weeks one, two and three for essential updates. Our comprehensive guides prepare you for what’s to come. We also provide important tips to optimise your health and all the latest pregnancy developments.

2. Take a Pregnancy Test

In week three, we discussed how taking a test too early may affect reliability. Now you’re four weeks in, it could be time to take that test, especially if you’re displaying early symptoms or have missed your period.

That said, while the accuracy of these tests is high over the days you’ve missed your period, there might not be enough hCG in your urine to reflect a positive reading. Wait until you see two lines, or have your period before you stop testing.

3. Make a Prenatal Appointment

Booking a Prenatal appointment is a good Consideration during the early weeks of Pregnancy

You can now schedule a visit with your healthcare provider once you’ve obtained a positive pregnancy result. While you might want to see your doctor immediately, the earliest appointment you’ll get is when you’re eight weeks along. It might seem like a long wait, but there’s no reason for an earlier booking if you’re healthy and undergoing a textbook pregnancy.

Remember the first day of your last period when phoning to make your appointment. This information is vital for calculating your due date, how far into your pregnancy you are, and when to book your first prenatal appointment.

4. Look After Your Mental Health

After experiencing the immediate joy of learning you’re pregnant, you might also feel overcome by stress, uncertainty, and anxiety. Albeit exciting, bringing new life into this world presents certain risks, dangers and challenges.

Once you become a parent, you have a lifetime of worrying about your child’s well-being, starting with everything that might go wrong in utero. It’s hard not to have worst-case scenarios running through your head. But try to live in the moment instead of constantly skipping ahead as stress can have a damaging effect.

If you can’t manage your anxiety or negativity, contact a mental health professional for help. Otherwise, seek out counsel and support from your partner.

5. Take Your Vitamins and Limit Certain Foods

We know we sound repetitive, but good nutrition during pregnancy is vital.

Vitamins and minerals, particularly folic acid, calcium and iron, are recommended for your baby’s health and development. However, consult with your doctor before you take anything. While you need additional vitamins and minerals for pregnancy, others, like Vitamin A, are harmful to your baby and must be avoided.

Besides vitamins, you should also eat healthily. Your pregnancy diet should be colourful and include many fruits and veggies, protein and whole grains.

Pregnancy cravings (which could start soon) that sometimes give you a hankering for strange foods and snacks can make it challenging to follow a nutritious diet. But try to be as healthy as possible. We recommend that you keep your sugar and junk food intake to a minimum and don’t skip meals.

On the flip side, your menu during pregnancy grows smaller as the list of forbidden foods grow larger. Boozing, indulging in soft cheese or binge-eating raw sushi are out.

You might have to restrict your diet further because while certain foods are safe, they won’t make you feel good. Add spicy food, white bread, and fizzy drinks to the foods you should eat cautiously.

6. Don’t Take Drugs, Drink or Smoke

Everything you consume crosses your placenta. This means that good and harmful substances are transferred to your baby, either supporting or harming their health and development.

That said, there’s no safe amount of alcohol you can drink or cigarettes you can smoke. Both substances can have devastating health consequences for your baby.

Although legal in certain parts of the world, the same applies to marijuana. You should also avoid illegal recreational drugs.

Many medications are safe for pregnancy, but a few can cause birth defects. Consult your doctor if you’re on chronic medication to see if you can continue to take them.

7. Rest When You Can

During Week 5 of Pregnancy, expect fatigue to start increasing!

Pregnancy exhaustion isn’t like the tiredness you experience after a Netflix binge or late-night Instagram scrolling. This you might find maddening. Doesn’t fatigue and sleep deprivation come after the baby’s arrival?

Unfortunately, this fatigue is ongoing, especially during the first and last three months of pregnancy. You might experience renewed vitality during the middle parts. However, tiredness will return as your birth draws nearer and you have more to carry. 

You can beat the dreaded pregnancy fatigue in these ways.

  • Nap during the day to catch up on lost sleep (your pregnancy bladder might keep you from having uninterrupted rest). You can always nap at lunch if you work from home. 
  • Working out might be the last thing you want, but light physical activity provides much-needed energy. 
  • Drink plenty of fluids. Dehydration harms your and your baby’s health, which might explain why you’re depleted. 
  • Eat and snack regularly and avoid sugar-laden food and beverages that make you extra sleepy. 

8. Soothe Your Tummy

Your stomach might suffer the worst pregnancy symptoms, from bloating to gas to an upset stomach. Fortunately, easy ways exist to ease or avoid abdominal discomfort and illness. For example, try eating several small plates of food throughout the day instead of consuming two or three big meals. This eating method also reduces morning sickness if you can’t keep anything down. 

Also, eating too fast makes you swallow more air and causes bloating. If this is you, focus on slowing down and chewing your food more. 

10. On Managing Queasiness

Drink ginger tea during week four pregnancy to reduce nausea symptoms

Inarguably, morning sickness is awful and disruptive. However, you can improve the experience by eating a snack first thing in the morning or asking your partner to prepare your meal so you don’t have to. 

There are many ways to relieve morning sickness, but this is our top advice. If you can’t stomach anything -ginger tea, bananas, and broth are the easiest to digest. Never miss meals even if you’re not hungry – an empty stomach can exacerbate nausea.

Do I Need an Ultrasound During Week Four of Pregnancy?

As a little dot on a screen, it’s not much to look at, nor does it have a heartbeat. Therefore, it’s too early to track your baby’s progress with an ultrasound, but it could be nearly time to book one! While you might hope to see your doctor immediately and have a sneak peek of your future baby’s progression, you’ll need to wait until you’re at least eight weeks pregnant or six weeks for high-risk pregnancies. The good news is that you now have a fast-approaching date on your calendar!

Fun Fact For Pregnancy Week Four

  • Are you tasting pennies? A metallic taste in your mouth is a weird pregnancy symptom that can ruin food for you.  It’s a medical condition called Dysgeusia that can be neutralised with lemonade or vinegar.
  • Try Pilates or Yoga if you’re looking for pregnancy-friendly exercise. Pilates offers many health and body benefits. Not only is it effective against stress and for promoting relaxation, it but helps you adapt to your changing body. Plus, this study shows that pilates during pregnancy eases aches and labour pain.

Week Four Pregnancy Checklist

  • A pregnancy test might come back positive – buy some.
  • Book your eight-week prenatal appointment now!
  • Pregnancy is a lot to digest and unpack – prioritise self-care.
  • If you haven’t already, catch up on your week one to three readings.
  • No more booze, cigarettes, marijuana or other substances!
  • Rest and take naps – growing a baby is tiring!
  • Cuddle up on the sofa and work your way through our (COMING SOON) Week 5 Article!











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I'm the person who wrote this

Julie Y

“Hi! I’m Julie, one of the Admin over here at The Baby Edition!

I extensively studied Children whilst completing my Degree in Psychology, with much of my research being based on the Development of Twins! Since then, I have continued to work with vulnerable families, and raised a child of my own in the Meantime!

Even to this day, I’m constantly researching Topics relating to Parenting, and love sharing what I have learned with our wonderful Readers!”

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