Month by Month: Each Trimester of Pregnancy Explained

Month by Month: Each Trimester of Pregnancy Explained

Month by Month: Each Trimester of Pregnancy Explained


Pregnancy can be a daunting time, especially if you’re a first-time mother or aiding a first-time mother. Being informed and prepared of what lies ahead is the best way to stay one step ahead, keep your mind at ease, and help you relish the joys of motherhood. You’ll be ready for anything and everything. Here’s a breakdown of each week; what the baby looks like, how it behaves, and what to expect in the weeks to come…


First Trimester: Weeks 1-12 


The best way to tell if you are pregnant is by a missed period. A home HCG pregnancy test can be taken at least 1 week after the last period. Blood tests can be done for a quicker result. The first trimester is marked by some discomfort and mood changes. Some mothers may experience nausea, fatigue, tender breasts, and frequent urination. Eating smaller meals at frequent intervals to combat cravings. 


At month 1, the fetus will: 

  • Be the size of a grain of rice, only 1/4th of an inch 
  • Form a primitive face with dark spots for eyes
  • Have a mouth, throat, and lower jaw
  • Create blood cells and start circulation 


At month 2, the fetus will: 

  • Be about an inch in length, and can be officially termed a “fetus”
  • Form tiny buds which eventually become the limbs 
  • Develop a central nervous system, digestive tract, and sensory organs
  • Replace cartilage with bone 


At month 3, the fetus will: 

  • Form arms, legs, fingers, and toes
  • Be able to open and close its fist 
  • Start to form teeth 
  • Have a circulatory and urinary system 


Second Trimester: Weeks 13-26 


The second trimester is often called the “golden period”, as it is marked by much less discomfort than the first trimester. A lot of unpleasant side effects seem to go away, and a mother will be able to feel the fluttering movements of her baby. However, other side effects like back pain, abdominal pain, constipation, leg cramps, and heartburn may set in. Yoga, meditation, exercise, and healthy eating can help combat painful and uncomfortable symptoms. 


At month 4, the fetus will: 

  • Rapidly grow, and reach about 4 ½ inches in size
  • Develop bone structure 
  • Be able to move his or her eyes, and start coordinating body movements  
  • Develop thicker skin 
  • Form external genitalia, meaning you’ll be able to tell the sex of the baby


At month 5, the fetus will: 

  • Reach about 6 ⅓ inches in length 
  • Have fully developed ears and may hear sounds
  • Become pretty active, rolling and flipping in the amniotic sac, at which point mothers will be able to feel the little flutters
  • Form a thick, greasy coating called the vernix caseosa, which protects the baby from cuts, abrasions, and hardening from the surrounding amniotic fluid


At month 6, the fetus will: 

  • Be nearly 9 inches in length, and weigh 2 pounds 
  • Be able to suck his or her thumb 
  • Have visible hair and eyebrows 
  • Form fingerprints and footprints 
  • Develop lungs 
  • Be able to respond to your voice 


Third and Final Trimester: Weeks 28-40 


The final trimester can be a physically and emotionally taxing time for the mother. Due to the increased size and 2.5 pounds of uterus weight she has to carry around, there may be a lot of complications at this stage like varicose veins, hemorrhoids, urinary incontinence, and breathing and sleep issues. She may experience Braxton-Hicks contractions, which are random, usually painless spasms of the uterus, and will feel a lot of movement from her baby. This trimester also brings a lot of anxiety to new mothers, but staying positive and prepared will help keep your mind at ease. 


At month 7, the fetus will: 

  • Be about 13 inches long 
  • Have fully developed hearing
  • Respond to stimuli like sound, pain, and light 
  • Change positions quite frequently


At month 8, the fetus will: 

  • Be 18 inches long and weigh about 5 pounds 
  • Develop body fat reserves 
  • Have matured internal development systems 


At month 9, the fetus will: 

  • Be about 18-20 inches long and weigh anywhere from 7 to 9 pounds 
  • Have early fully developed lungs 
  • Have coordinated reflexes 
  • Change position for delivery 


Pregnancy and birth are truly miracles of nature, and going through the experience can change a family for the better. Be sure to provide as much support to the mother as possible, and reach out to an OBGYN for any information.  



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