The first 12 weeks of your pregnancy will probably be the most significant adjustment period. You get used to the idea of being pregnant, make some lifestyle changes, and deal with all of the physical and emotional changes. The first trimester is thought of as the most sensitive time during your pregnancy. This is when your baby is building organs and structures. You may not see a whole lot going on outside during the first trimester. You will be able to tell many changes are going on internally. Get an overview of everything you can expect during the first trimester of your pregnancy. This article covers common symptoms like morning sickness, changes in hormones, your baby’s development, and how you can get some relief from some of the not so fun side effects of being pregnant.

For a week by week breakdown of what is going on with you and your baby, check out the 40 Weeks podcast.

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First Trimester Overview

The first trimester spans the initial 12 weeks of pregnancy. This will probably be the most significant adjustment period for you. The first 12 weeks are also a major period of growth and development for your baby. This is thought of as the most sensitive time during your pregnancy. The first trimester is when your baby is building organs and structures. For a week by week breakdown of what is going on with you and your baby, check out the 40 Weeks podcast. You may not see a whole lot going on outside during the first 12 weeks, but you will be able to tell there is a whole lot going on internally and emotionally.

First Trimester Hormones

Conception is usually two weeks into your 40-week pregnancy. The first two weeks, your body is doing what it does every month to prepare your uterus in case you do conceive. Conception occurs in week three. Once the egg is fertilized, the part that will develop into the placenta starts producing the pregnancy hormone hCG (human chorionic gonadotropin). HCG is the hormone a pregnancy test detects. In addition to telling you that you are pregnant, hCG does several essential things. It tells your ovaries to stop releasing eggs and triggers increased production of estrogen and progesterone. Estrogen and progesterone are going to rule your world for the next nine months. These hormones control just about every part of the process of pregnancy.


As your pregnancy progresses, changes in hormones can make your moods swing all over the place. Please know that this is normal. These hormone changes are why you feel fine one minute, then sad or angry or agitated the next. As your emotions are running wild, you may also find yourself worrying about your relationship, finances, work, and your baby. Don’t stress out. Everything will work out. It seems like a lot initially, but you will learn what you need to and figure out solutions as you go. Having a baby is a major life change, and you aren’t going to come up with all of the answers overnight.

Your Partner

If you have a partner present, keep an open line of communication with your partner. This is crucial, especially once you have a baby. If either of you has any doubts or worries, share and work through any concerns together. A healthy relationship with your partner will create a strong foundation and positive environment for your baby. Involving your partner in your pregnancy is a must. Start with everything dads and partners need to know.

Common First Trimester Symptoms

There are many common symptoms of pregnancy, and you will probably experience quite a few of them.

Morning Sickness

Morning sickness doesn’t always happen in the morning. You may be nauseous at any time or even all day. This can start as early as three weeks after conception and usually ends around the 12th week, right when you begin the second trimester. If you do not have any morning sickness count yourself lucky. Your body is producing a ton of estrogen and progesterone, which contribute to nausea. While you are pregnant, you also have a heightened sense of smell, so various odors — such as certain foods cooking, perfume, or cigarette smoke — might cause waves of nausea in early pregnancy.

There are a few things you can do to help relieve nausea. Eat small, frequent meals throughout the day. Choose foods that are low in fat and easy to digest. You will obviously want to avoid foods or smells that make your nausea worse. It’s also helpful to drink plenty of fluids, mostly water. Ginger can be helpful. You can try ginger ale or ginger tea, which may make you feel a little better. Many women say that peppermint oil helps if you are into essential oils. Motion sickness bands may also be helpful, acupuncture, and acupressure. If you are having a really tough time with morning sickness and can’t keep down liquids, please check in with your doctor or midwife.

Other Physical Changes

You might have a stuffy nose, sometimes classified as pregnancy rhinitis. This is an inconvenience, but it will go away eventually.

Your breasts will get a lot bigger, and they will probably be really sensitive and tender. One thing that may help if your chest hurts is wearing a comfortable and supportive bra or sports bra. For an in-depth explanation of all of the changes, you can expect with your breasts, see this article.

If you are waiting to announce your pregnancy until the second trimester, you shouldn’t start to show until the end of the first or beginning of the second trimester. If you are expecting twins or if this is not your first pregnancy, it may be sooner. You may be able to get away with your current clothes until the second trimester. Please do not suffer in uncomfortable clothes. Eventually, you will want to get some maternity clothes.

You will probably have to pee all the time. As your uterus grows, it puts pressure on your bladder, which can even cause you to leak a tiny bit when you sneeze, cough, or laugh hard. If you are worried about leaking, you can always use a panty liner, and no one would know. Although going to the bathroom a hundred times a day can be annoying, you need to stay hydrated. Please don’t skimp on drinking water.

As your levels of progesterone increase, you may find yourself tired and wiped out. Don’t fight it. If your body is telling you it needs extra rest, listen to it. Pregnancy fatigue is most common in the first and third trimesters. Taking a prenatal vitamin, eating healthy, staying hydrated, and being active may also help fatigue. Sometimes the best thing you can do is relax, rest, take a nap, or go to bed early.

You may find yourself sick at the thought of certain foods and craving things you do not normally eat. These changes in food preferences are common, and a result of all the hormonal changes going on.

When you are pregnant, your body slows down the digestive process. On the positive side, this gives nutrients more time to be absorbed into your bloodstream and reach your baby, which is awesome. Unfortunately, it can also lead to constipation and heartburn. Hydrating and getting enough fiber will help with constipation. Heartburn is caused by hormones relaxing the valve between your stomach and your esophagus, which allows stomach acid to leak into your esophagus, and this may cause heartburn. You can minimize heartburn by eating small, frequent meals, and avoiding fried foods, carbonated drinks, citrus fruits or juices, and spicy foods.

Exploring Your Birth Options

You will want to explore some options as to where you want to have your baby’s birth. I urge you to keep an open mind and visit several places before making a decision. The majority of births in the U.S. take place in a hospital. If you are open to it, check out your options to have a home birth, or visit a birth center. It is easy to have preconceived notions that can be wrong about what a particular hospital or birth center will be like. Even if you want an unmedicated birth, you can have a natural birth in the hospital.

Visits with Your Doctor or Midwife

Your prenatal care will be with a doctor or a midwife. There is only so much research you can do before you meet your care provider. If you hit it off, great. If you don’t, do not hesitate to change and find someone else who is a better fit. The overall theme of your prenatal care should be working with someone, or with a team, to learn what is going on, ask questions, and prepare for the arrival of your little one. Click here for tips on choosing or changing your care provider.

Your first prenatal visit will probably be around the eight-week mark. Those weeks leading up to this visit can seem like forever. This episode outlines what you should be doing before your first appointment.

The first thing you will do at your appointment is to take a pregnancy test. The next thing is they will figure out what your due date is. This is done with a calculation based on your last menstrual period and will later probably be confirmed with a measurement on an ultrasound. While the due date is rarely the actual date your baby will show up, it is a relatively close estimate. If you know when your last period was, this will be helpful. You want to get this as accurate a possible in the beginning because so much of your care and a lot of the recommendations from your doctor or midwife are based on your due date.

There are routine things that you can expect to happen at each checkup. Your care provider should be asking how you feel if you have any questions, and it is important to communicate to make sure you understand everything. Communication with your care provider is critical. Here are five tips to make the most out of every prenatal appointment.

Yes, you will have to step on a scale every time. The average woman gains weight between 25 to 35 pounds throughout your pregnancy. This is based on being average weight before getting pregnant. Generally, if you are underweight, you should gain 28 to 40 pounds, and if you are overweight, you may only need to gain 15 to 25 pounds. In general, you should gain about 2 to 4 pounds during the first trimester and about a pound a week for the remainder of your pregnancy.

You can also expect to have your blood pressure taken at each visit and usually give a urine sample several times during your pregnancy.

Checking on Your Baby

In addition to checking on your health, your care provider will also, of course, check the health of the baby. This is done by listening to the baby’s heartbeat, which is much faster than an adult’s heartbeat. Your baby’s heart beats about twice as fast as yours does. There are several ways the heartbeat can be heard, from doing a full ultrasound to using a Doppler, which detects the heartbeat with soundwaves, to using a simple stethoscope.

Prenatal Tests

Several prenatal tests will be offered or suggested to you during your pregnancy. Make sure you know your options, along with the risks of each test. Some tests just take a sample of blood from you and are considered non-invasive, and some tests, like an amniocentesis, actually take a sample of the amniotic fluid. This invasive test carries a risk of miscarriage. You may feel like you are continually waiting for the result of some test to come back so you can be assured that your baby is healthy. Please try to not stress out over any tests! They are routine, and you have a high probability of everything checking out fine.


With all this talk about doctors, don’t skip the dentist. The health of your mouth, and especially your gums, can impact your baby. It is important to keep up dental care during pregnancy.

Your Growing Baby

The first trimester is a period of really rapid growth for your baby. At conception, your baby is a single cell. When the egg is fertilized and chromosomes from the mom and dad are combined, the biological sex is already determined, although it will be a while until you can find out.

Your little one starts out looking like a tadpole, but as they grow, they become more and more human-like in appearance. During the first trimester, all of your baby’s organs will begin to develop, and some will even start to function. This means that the first trimester is when your little one will be most vulnerable to anything that might interfere with development.

As your baby grows, they will be busy kicking and stretching, and they may even have the hiccups. It will still be another couple of months before you can feel them moving around. By the end of the first trimester, their heartbeats, pumping blood, their facial features will begin to appear, baby’s arms and legs are growing longer, fingers and toes have started to form, and they even have fingernails.

At 12 weeks, your baby weighs about half of an ounce, and they measure around two and a half inches from crown to rump. Babies in utero are measured from the crown of their head to their bottom since there are folded up to fit inside your uterus. Once they are born, the length is measured from head to toe. Your baby is about the size of a lime or a plum this week if you like comparing your baby to fruit.

The 12-week mark also means the chance of miscarriage drops, so you can breathe a sigh of relief. This is also about the time a lot of people are comfortable announcing their pregnancy to the world.

Thank you to the amazing companies that have supported this episode.

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