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A Break Down of the First Trimester Week by Week

The first trimester of pregnancy is an exciting time, especially if it’s your first baby.  The first trimester will include huge milestones in your baby’s development, such as your first doctor’s appointment, first ultrasound, hearing your baby’s heartbeat, and the dreaded morning sickness.  Let’s get started by breaking down those first 13 weeks of your pregnancy.

Week 1

first trimester

The first week of your pregnancy is fairly uneventful because technically you aren’t aware of your pregnancy yet.  Later when you become pregnant, you will get to count back to the first day of your last period and count that as week 1.  A pregnancy is considered 40 weeks long even though you only carry your baby for 38 weeks.

If you are trying to get pregnant, it’s a good idea to start taking a prenatal vitamin with folic acid in it, this first week.  Folic acid is a B vitamin that can help to prevent spina bifida.  This small act of taking folic acid can immensely change the life of your future baby.  Also, if you are a smoker or heavy drinker, there is no better time than now to stop.

Week 2

first trimester

During the second week of your pregnancy, you still aren’t yet pregnant.  Just like week 1, you will need to count backward after becoming pregnant when you call this your second week of pregnancy.  During week 2, ovulation occurs.  To increase your chances of becoming pregnant, it’s best to have intercourse a couple of days before ovulation and continue every other day until you are sure you are finished ovulating.  Make sure to continue a healthy lifestyle including working out, staying well hydrated, and getting plenty of rest.

Week 3

first trimester

This 3rd week is when a lot of pregnancy action starts.  This is the first week where you may actually be pregnant.  Chances are at this point you won’t have any symptoms.  However, some women say they can just feel that they are pregnant by week 3.

During this week, make sure to not take any medications without checking with your doctor.  I remember having a dentist appointment in my small town during week 3.  On the intake form, it asked if I was pregnant and I checked yes, even though there was nothing official to confirm that.

The whole office was excited for me. So much for confidentiality, but it was fun to share the excitement even though it was a bit sooner than I planned to tell, as I didn’t know for sure, but I just felt pregnant.  And I was indeed pregnant with a 12-year-old daughter now as proof of it.  The reason this question is asked on medical intake forms including even a dentist is so that you won’t be given any harmful medications that could harm your very tiny baby.

Week 4

first trimester

Week 4 is a very exciting week of pregnancy because a home pregnancy test can now pick up on the fact that you are pregnant.  You may start to feel crampy, bloated, moody, and tired.  This is also the week where you may start to experience your first taste of morning sickness accompanied by sore breasts.  Some women even start to feel the frequent need to pee, this early on.  For other women, the need to pee frequently doesn’t start so early.

Now is a good time to buy a larger bra if you need it.  Some women experience a cup or more size growth by week 4.  Make sure to avoid chemicals like paint fumes and cat feces.  This means no more changing the cat litter box for you until your baby is born.  Cat feces can carry a parasite that can cause toxoplasmosis, which is harmful to your baby.

Week 5

first trimester

Your baby is now about the size of a tiny grain of sand.  Incredibly even at this microscopic stage, your baby’s heart is pumping blood, and other organs have started to develop.  Your child’s arms and legs have started to form.

During week 5, many women start to forget things and feel like they have brain fog.  Now is a good time to make an appointment with your doctor or midwife.  Some doctors may not want to see you until week 8.  During your appointment, you will pee in a cup to have it analyzed, and most likely your doctor will try to detect a heartbeat on an ultrasound.  Hearing your baby’s heartbeat for the first time is an incredible experience.  I didn’t expect to cry, but when I heard my daughter’s heartbeat for the first time, the tears started flowing.  Make sure that you call to schedule a doctor’s appointment at this time.

Week 6

first trimester

During week 6 some women experience an early miscarriage.  Some experience this before they realize that they were even pregnant.  If you are taking care of yourself, there is nothing that you can do to prevent a miscarriage.  Be careful not to consume too much caffeine as some studies have suggested that 300 milligrams or more of caffeine may lead to birth defects.  This is the week when some people tell their family and friends that they are expecting.

Week 7

first trimester

During week 7, your baby is about half an inch long.  This is the week where morning sickness may be kicking in big time for some women.  Don’t be alarmed if you don’t feel morning sickness yet.  Some women find that they are extremely hungry by week 7.

If you are experiencing morning sickness, it should help to consume very small snacks throughout the day.  Make sure to stay well hydrated which may also means taking very small drinks of water.  Some women find that ginger helps to curb the effects of morning sickness.

Week 8

first trimester

This is the week where you may be able to hear your baby’s heartbeat with an ultrasound machine at your doctor’s office.  Hearing the heartbeat is a great sign that your baby is alive and viable. This can be a stressful time for some moms.  When you hear your baby’s heartbeat, the chance of miscarriage drops drastically to the single digits.  At your 8-week doctor’s appointment, you should get your due date.

Week 9

first trimester

Week 9 may start to feel uneventful, but rest assured big changes are happening inside your womb.  Your baby is now approximately 1 inch long.  The legs have lengthened, and the toes are starting to form.  Your baby’s arms now have elbows that have begun to bend.  The fingers are starting to form on your baby’s hands.  Internally, your baby now has a liver, gallbladder, spleen, and adrenal gland.  Your baby is starting to move around more, even though you won’t yet be able to feel the movements.

Week 10

first trimester

Week 10 can feel just like week 9 as if nothing is happening.  You probably have not gained much weight the last couple of weeks, even though your baby is making rapid changes inside of you.  Your baby is now able to swallow fluid and kick.  His or her brain is now in place and functioning.  Little nails are forming on the fingers and toes, and fuzzy body hair is starting to grow all over his or her body.  Your baby’s skin is very translucent so the spine can be seen.  I remember week 10 because I read in my Mayo Clinic book at the time that I was pregnant, that my baby was now the size of a fun-sized candy bar. Somehow that image just made me smile, and it still does.

Week 11

first trimester

Right about now, you may be in full blown morning sickness, which by the way, can happen all day not just the morning as you may know full well.  Or you may be having some really strange cravings.  Some people feel like the cravings mean you are deficient in something.  A good rule of thumb is if it’s a healthy craving eat it. If it’s junk food, chances are it’s just a random craving, and skip it if you can.

Week 12

first trimester

Your uterus is now outside of your pelvic bones.  By week 12, the chances are that you have a baby bump.  Avoid exercises that require you to lay down on your back.  Your baby may put too much weight on a major vein which can cause decreased blood flow to your baby.  It can also make you feel lightheaded.

Week 13

first trimester

Congratulations are in order when you make it to the 13th week of your pregnancy.  This means that you have finished the first trimester of your pregnancy.  Your chances of miscarriage decrease greatly after week 13.  Plan on starting to gain more weight and showing more the next trimester.  By the 13th week, your baby is about the size of a lemon.

Final Thoughts

A lot goes on inside your body during the first trimester.  Even though you may not see a lot of weight gain or even feel pregnant other than having morning sickness, you now have a living person rapidly growing inside of your body. I hope that the tips and information I provided today can help to prepare you for your first trimester!


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