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Everything You Need to Know About the First Trimester of Pregnancy

Everything You Need to Know About <br> the First Trimester of Pregnancy

what to expect in your first trimester

Dates: The Start of Your Last Period – The End of Week 12

You stare at the positive pregnancy test, your heart racing. The sense that life is about to change completely washes over you. Everyone reacts differently to this monumental news, and whether you’re excited, apprehensive, or nervous, we’re here to guide you through the tidal wave of emotions and physical changes that are about to begin for you and your baby.

For many people, the more they know about any new endeavor, the more comfortable and confident they feel. We've done the research to bring you the best information available about what you can expect during the first trimester (check out these survival tips!). We’re here for you, and we know you've got this!

First Trimester Baby Development

first trimester baby development, how baby changes during first trimester

Your baby will change a lot during the first trimester, rapidly developing from the first hints of life into a peach-sized fetus. Here are some of the things happening as your baby grows:

Week 1: It’s possible you have a sense of when your baby was conceived, but the truth is that pinpointing the exact moment pregnancy begins can be difficult. Because of this, your pregnancy is considered to begin on the first day of your last period.

Week 2: The next step is fertilization. This is what happens when a sperm meets up with one of your eggs and combines to create a wholly new chromosomal life. Though you may not feel any changes in your body, a lot is going on for your baby. Fertilization determines physical characteristics like eye color, hair color, and even biological gender.

Week 3: The fertilized egg moves through the fallopian tube to the uterus. At this point, your body begins producing enough human chorionic gonadotropin (hCG) to disrupt your menstrual cycle, and pregnancy tests may be able to register that you’ve got company!

Week 4: The embryo splits in two creating the placenta, which delivers nutrients and oxygen to your baby throughout your pregnancy. During this stage of development, the brain, spinal cord, and backbone form. The optic nerve also begins to form, laying the foundation for your baby’s eyes and vision. Implantation generally occurs this week, which means that the fertilized egg finds its home in your uterus. This can sometimes cause light bleeding.

Week 5: Though your baby is still tiny, he or she is developing rapidly. You will begin to feed your baby through the umbilical cord. Your baby’s shape becomes more distinct as it separates into three layers—the ectoderm, endoderm, and mesoderm—through which your baby’s organs, skin, and nerves grow. Even though your doctor will not yet be able to hear it, the first element in your baby’s heart will begin to pulse, a movement that can be visible by sonogram.

Baby development, what to expect first trimester

Week 6: This week, as your baby’s bones grow, arms, legs, hands, and feet may be noticeable in sonograms. By the end of this week, your baby will have tripled in size. The heart finds its rhythmusually around 150 beats per minute, twice as fast as an adult’s. Brainwaves are present as the cerebral cortex fires up, and highly specialized connections take place between the neurons and spinal cord.

Week 7: Facial features begin to form, with evidence of ears and a mouth and dark spots for the eyes and nostrils. About 100,000 brain cells are produced each minute! Your baby may be moving, but the motions are so small, you won’t feel them until the second trimester.

Week 8: Over the last two weeks, your baby has quadrupled in size. Facial features are more distinct, and touch receptors in the lips and nose form. As eyelids take shape, the retinas begin to develop. Hair follicles, nail beds, and intestines form. The brain directs intentional movement of limbs. Taste buds connected to the brain also form.

Week 9: At this stage, many of your baby’s organs will have developed and continue to grow, and the head will be half the length of the body. Your baby’s heartbeat will become stronger and more regular. His or her reproductive organs form, but you won’t be able to visually confirm the biological gender for a few more weeks via ultrasound. (It’s actually possible to learn this information via a blood test as early as seven weeks!)

Week 10: Congratulations! By the end of this week, you will officially have a fetus! You can see adorable fingers and toes, although they will probably look a bit webbed and paddle-like. The kidneys produce urine, and the bones harden. Brain cell production is up to 250,000 neurons per minute.

Week 11: This week, your baby will have a growth spurt and double his or her weight! With that growth spurt, he or she will begin to inhale and exhale small amounts of amniotic fluid to strengthen the lungs. Your baby’s nose and lips become evident as the facial features continue to evolve. Some scans have even shown smiling babies!

Week 12: Touch receptors in the palms, feet, and genitals begin forming. The first bowel movement may occur this week. There is a lot of stretching, kicking, and wiggling as reflexes develop. Imaging may reveal your baby responding to a hand placed on your belly, though you won’t feel it for a few more weeks. At this stage, the fingers open and close, and the toes curl. By the end of the third month, your baby will have vocal cords, muscles, and white blood cells that will fight off germs. Most of the body surface, except for the top of the head and back, responds to touch.

Your Physical Changes in the First Trimester

first trimester body changes, how pregnancy changes your body

Every woman's earliest pregnancy symptoms are different. Some women swear that they could immediately tell they had conceived. Some women don't realize they are pregnant for a long time. Whenever it happens for you, at some point, you’ll start to feel a bit unusual. That's because from the moment you become pregnant, your body is preparing to nourish your baby. Your hormones will change rapidly, and that's likely to make you feel different.

Here's a little bit of what you might experience during the first trimester. But remember, everyone's first trimester can feel different, so try not to compare yourself to anyone else (though many people will have advice). Instead, try to tune into the incredible changes taking place in your body:

PMS-like symptoms: When you first become pregnant, you may feel similar to how you feel right before you get your period. Pregnancy and your period both shift your hormones, so the indicators can present in similar ways. Your pants may suddenly feel too tight, or your breasts may feel swollen and tender. Your skin may break out. Early pregnancy cramps and mood swings especially resemble PMS. The good news is that if you have felt these symptoms before with PMS, you have probably already developed coping mechanisms to handle them, like resting and using heating pads.

Aversions, cravings, and taste distortions: As your digestion slows and your hormones change, you may begin to experience changes in food preferences. Some foods may become suddenly intolerable, while others may become strangely alluring. This can feel confusing (and maybe even a little bit annoying), but it's a perfectly normal part of the first trimester. For many women, these changes in taste can be the first indicator of pregnancy. You may also experience changes in appetite. Your appetite may noticeably ramp up, but it's not always true that you will feel like eating for two, especially during the first trimester. Take note of what your body is telling YOU!

Nausea: During the first trimester, many women experience nausea—with or without vomiting. Though it’s commonly referred to as "morning sickness," don't be fooled by the name; many women feel sick throughout the entire day or at various, unpredictable times. If you feel sick to your stomach in the morning, try to keep a glass of water and simple foods like crackers next to your bed. That way, you won't have to get up from bed to get something to settle your stomach. Even a small amount of food can give you the energy you need to transition to the rest of your day. Some favorite remedies also include foods, drinks, and other products with B6 and ginger, like Morning Sickness Support from Sensible, our sister brand.

Changes in libido: Your sex drive may also experience an uptick or a downturn during the first trimester. Your changing hormonal makeup can impact your libido in either direction, though you may not feel any change in your sex drive at all. Whatever you experience, this is a time to communicate with your partner about what you want and need in the bedroom. It’s always important to honor what your body needs. During pregnancy, this is especially true, so be brave and open about your sexuality.

Extreme fatigue: Your metabolic rate is way above normal, so you need to burn more energy just to function. On top of the physical changes, the emotional ups and downs can make you feel mentally spent as well. If you’re experiencing fatigue, give your body a chance to relax and take a napor at least take it easy. You may not have time to take naps, or if you do have pockets of time to rest, you may be unable to fully relax. So do what you can given the constraints of your life. Do you work 9-5 five days a week? Perhaps try to go to sleep earlier to get in a couple more hours of rest. Evaluate your lifestyle to see if you can take short naps throughout the day and still be productive. Exercise can also help rev up your energy. Listen to your body and know that it should get better in the second trimester. If it doesn’t, check in with your healthcare team.

Thirst and frequent urination: Increases in progesterone and hCG cause increased urinary frequency, an early symptom of pregnancy. Body fluids start to increase during pregnancy, which means the kidneys work overtime to flush this extra fluid out. The low position of the uterus adds to the pressure you may be feeling. Keep water handy at all times and strategize so you can access a bathroom should the need suddenly arise!

Weight changes: When you become pregnant, you may wonder about the amount of weight you will gain throughout the process. It might be surprising, then, that during the first trimester, some women actually lose weight rather than gain weight; the opposite can be true as well. Each body has a unique response to hormonal changes, so don’t be alarmed if you lose or gain weight during the first trimester. If you are worried about weight gain or loss throughout your pregnancy, be sure to talk to your doctor. Remember to consider your emotions when it comes to weight and body image outside of pregnancy as well. We can be hard on ourselves for not being perfect, and the changes that you'll experience during pregnancy can bring up a lot of those issues. Talk about it with people you love and trust so that you don't bottle up those emotions.

First Trimester To-Do List

First trimester to-do list

So you may be thinking: Okay, I know what to expect, but what do I need to do once I suspect that I am pregnant? This to-do list will help you navigate all your first trimester tasks.

  • Even if you have taken an over-the-counter pregnancy test, it's a good idea to call your OBGYN to confirm your pregnancy with a blood or urine test.
  • Once you've confirmed your pregnancy, you'll want to begin your OBGYN prenatal visits. During the first appointment, your doctor will likely perform a number of tests to assess your overall health. These can include blood tests and a pelvic exam. After the first exam, you'll have subsequent appointments, approximately every four weeks in the first few months, which will take less time than the first. Be sure to ask any questions you may have. You may want to start a pregnancy journal to record your thoughts, feelings, and questions.
  • Talk to your healthcare team about the foods, beverages, and medicines you should avoid and which prenatal vitamin is best for you. It's likely that your doctor will bring a lot of this up in your prenatal visits.
  • Explore your options for childbirth. Many women prefer to give birth under the care of doctors and nurses (and access to pain medications) in a hospital; others may prefer to use alternative services such as midwifery and doulas at home or birthing centers. Even if you do prefer a hospital birth, you may wish to hire a doula or midwife. These are all possibilities that you'll want to consider early on. Ask your doctor questions about what will be right for you given your medical history and really think about what you want. Everyone in your life will have opinions about what is best, but ultimately, these decisions will be up to you and your family.
  • Decide when and how you want to tell people. The first trimester can be an exciting time, but it can also be nerve-racking. Only you can decide who to tell and when to tell them. You may want to shout the news from the rooftop, or you may want to tell only a core group of friends and family who will be able to support you no matter what.
  • Eat healthy, balanced meals. This can be difficult, especially with nausea and possible changes to your appetite. You may not be able to eat three square meals a day. Instead, you might eat several healthy snacks or small meals throughout the day. Focus on getting the right nutrients because your body will need fuel to handle the massive changes it is undergoing.
  • Start a baby budget. If you will eventually need childcare, it is never too early to think about the expense and weigh options such as daycare, babysitters, nannies, or family help, if available. Thinking about this at the beginning of your pregnancy will help you cope with the costs later on. Plus, in some cities, you might need to get on daycare waiting lists as soon as you can!
  • Assess your work environment for chemical exposure, physical exertion, and stress. Brainstorm ways to make your lifestyle more accommodating to your changing physical and emotional needs.

What KB Moms Remember about the First Trimester

Nothing will quite prepare you for the first trimester, but hearing from others who have gone through what you're about to experience can be helpful when you're feeling confused or overwhelmed. Talk to the women in your life who have been there, or reach out to the amazing women in our Facebook group, KindredMamas. Your experiences may not be the same as anyone else's, but knowing that you have a community of support can make all the difference in the world.

To get you started, here are some first trimester memories that KB Moms have shared. They reflect the variety of ways the first trimester impacted them both physically and emotionally:

“I survived on Gatorade, watermelon, and goldfish crackers. My life was fatigue with a capital F! I was so excited about becoming a parent and embracing all that meant. I wanted to scream to the entire world: I’M PREGNANT!”


“My biggest thing for the first trimester was nausea. Chasing after two kids two and under and being pregnant, it was hard to remember to eat, or even take the time to eat. But as long as I could keep something in my stomach, it helped to keep nausea at bay. That meant snacking on anything and everything. Fruit snacks, yogurt, baby carrots, bananas, apples, different berries —anything I could wash and keep on the counter to grab as I passed by! Nap when you can is my best advice. Working during my first pregnancy, I napped during my lunch break every day. I tried to nap when my kids nap and go to bed as soon as they go to bed.” 


“I lived on Saltines and Gatorade...and french fries. It was hard feeling bloated and crummy while most of the world had no idea I was pregnant.”


"The first time around, my first trimester was nerve-racking. I was petrified that something would go wrong (it didn’t), so I waited until almost 14 weeks to tell anyone besides my closest friends that I was pregnant. The second time, I told almost everyone I knew right away. By that time I knew that if anything happened (it didn’t), I’d need to lean on my coworkers and loved ones. Both times, I made sure to fill out the FMLA paperwork as soon as possible so I didn’t have extra worries when morning sickness got my day started off badly."


“During my first trimester, my breasts were so sore I couldn’t sleep. I would wake up in pain until I realized I had to start wearing a maternity bra. That's actually how I discovered Kindred Bravely! I was looking for a comfortable sleep bra and found the French Terry. I’ve worn one pretty much every night since I was eight weeks.”


Congratulations on the start of your journey into motherhood! We hope the information in this post has given you some insight into the next few weeks of your new life with your baby. You’ve still got a long way to go on this wild rollercoaster ride, so be gentle with yourself and do what's right for you throughout your pregnancy. Check out Everything You Need to Know About the Second Trimester for more tips!

Don't forget to make your journey as comfortable as possible with clothes that look and feel great!

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