Pregnancy Calendar: Your First Trimester Week-by-Week

pregnancy calendar first trimester
During your first trimester, you're eager to find out when your due date is, what's going on and what's to come! Read our post to get caught up on the basics!

Starting a pregnancy can often mean starting a whole new year. This, of course, means you need a brand new pregnancy calendar; a planner of sorts. Forget January 1st, you have nine months ahead of you full of activity, both inside your body and out! Now, your new year starts the day that the pregnancy test shows positive! Well, technically by then you’ve already started.

The first thing is first, of course, you want to know where you are in these nine months. Next, prepare for the first trimester week-by-week. It might fly by or feel like an eternity. Regardless, there’s a lot going on in your body and for many women, it’s an inspiring image to follow along. 

In this post, we’ll go through ways to follow your pregnancy, your first trimester in baby size, baby development, and first-trimester diet and nutrition do’s and don’ts. This way, at least the first three months of pregnancy you’ll be more or less ready for what’s ahead. Want more info on your specific pregnancy and medical recommendations? Please consult your doctor to make sure that all recommendations you apply from outside sources (including this one) are appropriate for you. 

Let’s get started!

Guide to this post

pregnancy calendar calculator

Pregnancy Calendar: Calculating Months & Due Date

To know where you are in your pregnancy, you can use a pregnancy calculator like the one below. Granted, what these pregnancy calculators do is take the date of your last period and how long your cycles usually last and figure out what your rough due date should be. 

Due Date Calculator
When did your last period start?
Generally, how long are your cycles?
Calculate your due date
Your baby is likely to be born on or around*
*Only your physician can accurately determine your due date or the date of your conception based on his/her knowledge of your complete medical condition.
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In partnership with Clearblue®.

A Note on Due Dates 

What are due dates? Due dates, the date you receive at your doctor’s office is called an “expected delivery date” and it’s the date 40 weeks from the last day of your last period.

When moms say their baby is “early” or “late,” it’s often because they’re going off of that EED. Really, most babies are born between week 38 and week 42 of pregnancy

Which Week is Which in Pregnancy?

Pregnancy is then often divided into trimester, often explained as the three stages. There is also a fourth trimester that is much less talked about during which your body continues to make changes. Even after your baby is born, your body will go through an adjustment period and even your baby will continue to develop and change. More on this to come below, though for this post we’ll focus mainly on the first trimester (weeks 1-12).

TrimesterWeeksMonths of pregnancy
4Birth- 12 weeks old1-3 months old
best apps to plan your pregnancy calendar

Pregnancy Calendar App : Best Apps for Pregnancy Planning

If you want something in your pocket helping you every step of the way during parenting, there is hardly anything better than downloading an app. 

Using a pregnancy calendar app you can follow both your baby’s progress and your own body’s needs. Many pregnancy planning apps offer a clear picture of pregnancy day by day with development pictures of your baby’s size and milestones. 

Sprout Pregnancy App  (Rated 4.7)

Sprout is highly recommended and falls under Apple’s “Essential Apps for Parents”. It’s a daily guide through pregnancy with a free and paid version. The premium version of the app includes 3D interaction with kicks and heartbeats as well as a pregnancy journal to add bump progress photos, thoughts and more. Like many other apps, it also includes information about your baby’s growth progress, checklists and other tools. 

What to Expect Pregnancy App (Rated 4.8)

The What to Expect App offers a personalized pregnancy documenting experience with development information, medically accurate articles, and more. Like Sprout, it also offers a journal for mom to document the process as well as opportunities for her to upload photos of her changing body. The what to expect app is also a community offering personal stories from other parents and videos to show you, well, what to expect! Additionally, their information is backed up by science, frequently updated and kept accurate by their team of medical and health experts. 

WebMD Pregnancy App

The WebMD app helps with what to eat, medications to avoid, and even the ability to add another baby for twin-specific content. Their full pregnancy glossary allows you to look up terms you hear from your doctor (or the internet) like “BraxtonHicks” and “Apgar Score” to make sure you’re fully informed from sources that truly know. All this and more on the free WebMD pregnancy tracker app.

Top Baby Monitor Apps It’s 2020 and you still don’t have your baby camera on your phone? No worries, in this post we’ll talk about the top baby monitor apps, baby monitors that have an app, if you can use your phone as a baby monitor and more. As our homes get more and more connected to our phones and smart watches, the way we keep it and our families safe changes. Home security cameras have actually replaced doorbells the way cell phones replaced landlines. As a result, it’s no surprise that baby monitors have moved so much farther than simply listening to your baby. Smart babies are, more than another option for keeping babies safe, the updated version of traditional technologies for monitoring our little ones. The best smart baby monitors have their respective apps where you can see the live video feed of your baby in their nursery, set up notifications and more! There are also options without cameras that are just apps that some parents opt for. Let’s take a look at some of the best baby monitoring apps for Android and iPhone. Guide to this post: -What baby monitors have an app? - Can I use my phone as a baby monitor? - How to turn your phone into a baby monitor? -Cloud storage safe wifi baby monitor apps What baby monitors have an app? Lots of babygear these days have apps. From the Snoo to the Hatch and more, tech is finding its way into nurseries as well as the rest of your home. Apps like the above control devices that rock your baby or play white noise for them during the night. While some look at this as a removed way of caring for baby, its intention is to allow parents to recharge while their baby gets the extra comfort they need without being overly aroused by their parents coming into the room. Any parent who doesn’t want to wake their child appreciates a way to remotely rock them or play sounds they enjoy. This, more than a disconnect between parent and child, allows them both to rest easier. Some popular baby monitors with apps include Cubo Ai, Owlet, Nanit, among many others. These top baby monitors tap into the need modern parents have to see baby anytime, from anywhere, understand their sleep better, and get alerts for important events (crying, motion, face covered events, etc.) Of course, lots of these monitors with apps do a whole lot more than that, but it depends which you choose. Here’s the interface of Cubo Ai, for example.

Read about the top baby monitor apps

Baby Center week by week (Rated 4.9)

Baby Center has been downloaded hundreds of millions of times and still keeps a 4.9 star rating! Countdown to your due date and follow all the baby center videos showing you each stage of your pregnancy. This app even starts helping parents before they conceive! From fertility, ovulation, prenatal and postpartum, this app seems to be the most comprehensive one of them all!

The Bump App

This Pregnancy tracker from popular source The Bump, is super interactive. It gives you an interactive 3D image of your baby’s growth as well as a catalog of baby products with reviews so you save yourself hundreds of hours of googling what you want to buy. Get daily content to understand what’s going on both in your body and your baby’s all 9 months of your pregnancy.

The Bump’s Planner+ proactively suggests questions you might want to ask your doctor ahead of your appointments and adds them to your calendar. Finally, prepare for your registry with the top baby registry in the US. The Bump tracks all the things you’ve registered on Target, Amazon, Buy Buy Baby and more! 

your first trimester is the most important and most vulnerable

Which Trimester is Most Important?

The first trimester of pregnancy is truly the most important. This is why parents often don’t disclose a pregnancy until around week 12. After that week, the chances of miscarrying are lower. By week 12, your baby’s organ systems and body structure are developed. For mom, the first trimester has the most nausea, fatigue, tenderness and other uncomfortable symptoms. Of course, this changes from one person to the next and while some women say the first three months of pregnancy were the easiest, for others they were the worst. As long as you’re staying on top of your health check-ups and following your doctor’s instructions, either can be totally normal.

First Trimester Pregnancy Symptoms: What Happens in The First 12 Weeks of Pregnancy?

What are the first symptoms of pregnancy?

Within the first few weeks after your missed period you’ll start to feel any or all of the following symptoms: 

  • Tender and swollen breasts
  • Nausea
  • A frequent need to urinate
  • Fatigue (varies)
  • Food cravings and disgust
  • Heartburn
  • Constipation
  • Emotional confusion (sometimes many feelings at once)
  • Extreme emotions (higher anxiety, emotional stress, mood swings)

These are just to name a few. Below, you’ll find a full list and the rough timeline when they tend to show up in pregnancies. 

What week do pregnancy symptoms start?

This also differs from woman to woman but in general, some symptoms have a certain timeline for appearing, if you’ll have them at all. 

SymptomsTimeline in weeks (from date of missed period)
Mild cramping and spotting1-4
Missed period4
Tingling or aching breasts4-6
Frequent 4-6
Motion sickness4-6
Mood swings6
Temperature changes6
High blood pressure8
Extreme fatigue and heartburn9
Faster heartbeat8-10
Breast and nipple changes11
Noticeable weight gain11
Pregnancy “glow”12

Pregnancy Calendar: First Trimester Week-by-Week 

Week 2 

This is when your ovulated egg will go through fertilization. Though many sources explain fertilization as the sperm penetrating the egg, actual fertilization doesn’t happen until 12-24 hours after. Soon after fertilization, the egg will start dividing into multiple cells and will make a little home in the uterine lining.

Week 3 

The little ball of multiplying cells- a.k.a. the “blastocyst” is making hCG, a hormone that tells your body you are officially pregnant and that it doesn’t have to continue releasing eggs.

Week 4

Goodbye blastocyst, hello embryo! It’s been about 4 weeks since your last period and (spoiler alert) the next one isn’t coming. You should be pregnancy test-official at this point. Still, your little embryo is so tiny it resembles a poppy seed.

Week 5

Your little embryo is growing fast and starting to look like a little tadpole. Soon, they’ll have a little heart which will give you that super satisfying beat at your ultrasound appointment! 

Week 6

Not such a little tadpole anymore. This little fetus now has the start of a nose, a mouth, and even ears! Inside their little body, the intestines and brain are forming. Size-wise, they’re still a little tiny fetus, which is why your weight gain is minimal and unnoticeable. At week six, your baby is about the size of a lentil.

Week 7

When we said your baby is growing fast, we meant it. From one week to the next, baby has doubled in size and now looks like a little blueberry with a tail. As their hands and feet develop, their fingers and toes are still stuck together and are slowly forming their shape from the arms and legs.

Week 8

No longer such a still one! Little baby has started moving, though you can’t feel it. Your baby’s nervous system is making its way through all of your little one’s extremities. Their respiratory system is developing, too, preparing for that first breath. Still, you baby is only the size of a kidney bean.

Week 9

We already have earlobes! And, as cute as it was, we said goodbye to the little tail. Baby still weighs less than an ounce but their growth is just getting started. Say goodbye to the super discreet bump, mommy’s about to get bigger much faster. 

Week 10

Much of the vulnerability of the first trimester is over. Your fetus is close to being fully formed and their skin is translucent. Fingernails are forming and their little arms and legs are starting to bend, soon to be just right for the fetal position they will take when they’re much bigger in just a matter of weeks. 

Week 11

Is that a kick? There’s also stretching going on and even some hiccups as the diaphragm develops in a healthy way. Yet, your baby is still just the size of a fig so these little kicks will probably go unnoticed for a little while longer. 

Week 12

Just how knees started bending, now fingers start to curl open and closed and their mouth starts to make instinctual sucking movements. Poke your bump lightly and your baby will feel it. Their movements, though, still just a fluttering you won’t entirely feel yet. 

Your baby ends the first trimester as big (or little) as a lime.

First trimester by weeks video

Diet & Nutrition: What to avoid during the first trimester

Despite being a very normal thing to see on your social media feed, pregnancy is still a health condition. It is diagnosed (announced) and tracked with doctor’s appointments throughout. 

As such, it comes with its specific instructions on how to best take care of your body and stay healthy as it navigates a whole new way of functioning which requires a lot more work! 

Here are the best things to eat (and to avoid) to feel your best and avoid any pregnancy risks to yourself and your baby.

What to Eat

“Eating well” is a common recommendation we hear from doctors and even parents and grandparents during pregnancy but what does that mean? 

  • Healthy groceries: Stock your kitchen with nuts, fruit, multigrain pasta, and yogurt to munch on when you get hungry. Having healthy foods will assure that when you reach for something, it’s actually giving your body the nutrients it needs. 
  • Bland, room-temperature foods and ginger for morning sickness. If those don’t do the trick, ask your doctor about implementing vitamin B6 or anti nausea medication.
  • Water! Yes it’s not technically something you “eat” but staying hydrated is vital during pregnancy. Make sure you keep your urine to a clear or pale yellow color.
  • Pregnancy superfoods: fruits, veggies, eggs, salmon, sweet potatoes, yogurt, walnuts, beans, avocado, lean meats and poultry, and vegetables like broccoli and leafy greens are your best friends during pregnancy! 
what to avoid your first trimester

What to Avoid

First and foremost, take the advice given to you by the medical professional you trust and that knows you well. Consult with them about any medications you took before you got pregnant and see if they’re still appropriate for pregnancy. Other than that, general things to avoid include the following: 

  • Smoking: this can cause miscarriage, placenta issues, and preterm birth, among many other risks. Look into ways to quit and know that it’s never too late to do it in your pregnancy, but the earlier the better. 
  • Alcohol: the risks of drinking alcohol can include low birth weight, learning development issues, attention span issues, language development problems, and more. 
  • Caffeine: this one is probably the hardest and maybe the main reason women are so tired during pregnancy? (don’t quote us on that theory). High caffeine consumption can overstimulate your body and cause miscarriage and other problems. You don’t have to give it up entirely, but the American College of Obstetricians suggests an 11 oz cup of coffee or less per day.
  • Anything that could have bacteria, parasites, or toxins like: 
    • Undercooked meat
    • Pasteurized soft cheese
    • Raw eggs (or anything containing them)
    • Sushi (or any raw fish)
    • Oysters
    • Raw sprouts
    • Deli-style salads


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Ximena is the Content Marketing Strategist at Cubo Ai. She follows plants, dogs, and babies on Instagram and almost no one else.