What Happens in Your Body During the First Trimester

Apr 3, 2023

Couple stands embracing in background together holding photo of an ultrasound to the camera in the foreground
Your baby is rapidly developing during the first trimester!

Your body changes and grows in many ways during the first trimester, including some things you probably didn’t expect. 

So you just found out you are having a baby? Congratulations mama!!🥳 

How are you feeling?! 

Overwhelmed?! Excited?! Scared?! Worried?! Stressed?!

You undoubtedly have many emotions, which may change every few minutes or even every few seconds. That is completely normal!

Whether you were planning to include this new little bundle of joy in your life, or it came as a complete surprise, it is best to be as informed as possible to help ease the nerves about what is about to come on this new exciting journey! 

Each trimester is different, so let’s start with what to expect during your first trimester. 

What Changes Should I Expect to Happen to My Body During the First Trimester?

Yes. Your body will change and adapt to provide the best environment for your baby. This is what we mamas do best! Always giving of ourselves to help our babies.👶

Your baby’s body structure and organ systems are developing during this period, so YOUR body will also change (even if you may not notice any significant “baby belly”) 

*Small side tangent: If you’ve been pregnant before, you may notice that you start showing a bit earlier than the first time around. It might even remind you of how your belly looks after a big burrito. (Don’t lie. We’ve ALL had burrito babies once or twice.) 

Not every pregnancy is the same, but…

Pregnancy Symptoms During the First Trimester


Yes, you’re right. It’s more than “just being tired.” You always feel exhausted, even if you feel like you’ve done nothing all day. **Which isn’t even true BTW (even if you did only leave the couch to pee eleventy-billion times) because you are growing actual human body parts!  So when your partner gets home and asks what you did today, you can say, this is your official permission to answer: 

“Britt said I *had* to rest, so I watched every episode of The New Girl, and I grew the baby’s fingers today. What’s your superpower?!?”** But I digress…

But MY GOODNESS, that fatigue will get you. I remember….

This is due to the increased hormone called progesterone. This hormone supports your pregnancy and increases the production of milk glands required for breastfeeding later on. So it’s necessary, but it will make you tired. Maybe. 

The only cure is lots and lots of rest! Please don’t feel bad for getting a lot of sleep. You need it!

Mood Swings

Well, there are many factors, including stress, fatigue and not enough rest, an annoying partner, and their grotesquely smelling lunch 😆, and yes, of course, back to blaming our hormones. The increased progesterone and estrogen will affect your level of neurotransmitters, which are brain chemicals that regulate mood. 

So you’re not being overdramatic. It’s all part of the process.😆 But if you feel like it is out of control, there’s a chance your body needs more support than it’s receiving. 

Pregnancy pulls A LOT of minerals and nutrients from your body, and if you’re not replenishing them, these nutritional deficiencies can lead to really anxious and even depression. 

This is something I experienced during my third pregnancy. 

It turns out that when your body is low on these essential nutrients and we’re not getting enough sleep, you start running on stress hormones like cortisol and adrenaline. 

Pair that will the increase of estrogen and progesterone, and you’ve got an emotional disaster just waiting to happen! 

Something that really helped me and might be a good resource for you as well if you feel this way is the book The Postnatal Depletion Cure. It’s worth checking out if you’re just not feeling yourself these days. 


Yes, the famous morning sickness…I don’t know why it’s called morning sickness because it can strike anytime and anywhere!🤢 It’s more like All-Day-Every-Day-Nausea. 

Morning sickness will be at its worst at the beginning of the pregnancy (usually, but not always, there is some relief in the second trimester)

Many studies prove that constant sickness is a good thing since it can be linked to an increase in hormones meaning you have a healthy pregnancy. 

One of the hormones in particular that can be the culprit of your not feeling well comes from the placenta. It’s called human chorionic gonadotropin(HCG). Plus, estrogen and low blood sugar levels are all factors during those not-so-blissful moments. So make sure you are eating enough calories and protein to keep those blood sugars in check.

I’ve got some great tips on reducing nausea during the first trimester in this post! 

Breast Tenderness

The good news…your boobs will get bigger and look great! (if that’s good news to you…I mean, after growing up and nursing 3 of my own humans, this would not be a welcomed change for me because they’re quite heavy these days BUT 12 years ago when I was pregnant with my oldest? This would have indeed been a welcome and exciting change for my body image!)

The bad news… growth usually isn’t super comfortable.😆 Your blood flow is increasing to your breast, and your milk ducts are getting larger, preparing you to breastfeed. 

So, yes, the cleavage will be great, but they might be too sensitive to “enjoy,” if you get my drift. This may also result in skin irritation and tenderness. You might even notice flaky skin or even dried colostrum around your areolas, resulting in itchiness or general discomfort.

Increased Urgency to Pee

Yes, you will feel the need to pee all the freaking time! The increase of the HCG and progesterone hormones (yes, those guys again) will cause this urgency to pee. 

Another factor will also be due to your uterus growing and putting pressure on your bladder. You can learn more about staying hydrated without having to pee ALL. THE. TIME here. 

The Things No One Tells You About the First Trimester 

Although these are the most common pregnancy symptoms, everyone has a different experience. There are a lot of other effects that you may feel you weren’t warned about, so let’s just go over a few more (as if the first batch wasn’t scary enough), so you won’t be too surprised if you feel any of these.

  • New sensitivities– Our bodies may react differently to items we’ve never had sensitivities to before. (I became allergic to K-tape adhesive and deodorant during my 2nd pregnancy. Unfortunately, I was gestating through the heat of an Oklahoma summer. So I probably wasn’t the most pleasant-smelling company. But if I tried to apply deodorant, I would break out everywhere that I came in contact with the product)
  • New smells– Our noses become more sensitive too. Be prepared to be grossed out by familiar smells throughout the day🤢. Laundry detergent, my freshly showered husband, and the freezer section at the grocery store were 100% triggers for me.
  • Acne– It’s not just for pubescent teens anymore…yay! 😮‍💨When you do notice the increased pimples popping up, they can feel SO sensitive (like having a sunburn!)
  • Increased blood flow– This will have all kinds of effects (depending on where the blood flows). It can cause swelling, hot flashes, varicose veins, increased sex drive/sensitivity🔥…and the list goes on.
  •  Body odor– All of the changes your body is going through will affect your body odor. It’s good to be aware of where the new smell is coming from and search for some helpful tips. For example, one of the factors could be a ph imbalance. Thankfully there are body washes that are made to combat that exact problem.
  • Body image struggles – Many mamas really struggle with their new bodies. They start to experience stretch marks, weight gain, breast changes, bigger clothing sizes, and even bigger feet, 🦶🦶. I am here to beg you to embrace and love your new body. 

How to Adjust to Body Changes During the First Trimester

Focus on what a powerful machine you are to be actually creating a whole-ass baby inside of you! Weight gain is necessary and may be very hard for mamas who have previously had an eating disorder. Fight the urge to go back to old extreme habits of losing weight for your baby and its needs. If you are feeling really compelled to restrict or expel your food intake, consider meeting with a Licensed Mental Health Counselor who specializes in perinatal transitions AND food relationships. 

Should My Diet Change Immediately?

Between the morning sickness, new smell sensitivities, and heartburn…well, eating nutritious  meals may be the last thing on your mind. While it’s not advised to go on a fast food binge, we don’t want you to lose weight from the lack of calories and nutrition. 

The good news is at this point your baby is surviving on the placenta right now, so it’s ok if your nutrition isn’t perfect because, at this point, you’re basically just surviving. But when you hold in that gag reflex and sneak away from the toilet long enough to grab a decent snack, try to focus on keeping your protein up and your sugar intake down. You’ll thank yourself later.

Supporting Your Body During the First Trimester

I hope this has helped you ease your mind into overthinking the unknown. Remind yourself of the bad-ass mama you are becoming, and cherish every moment with your new bundle of joy in your belly.♥️

In the meantime, check out my exclusive course, Comprehensive Birth & Baby Preparation Program, to help you feel prepared and confident for the coming months and years. 

You can join these Spokane birth classes in person if you’re local or online from anywhere in the world. I can’t wait to meet you! 

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