First trimester (week 1– 12)
During the first trimester your body undergoes many changes. Hormonal changes affect almost every organ system in your body. These changes can trigger symptoms even in the very first weeks of pregnancy. Your period stopping is a clear sign that you are pregnant. Other changes may include:
Extreme tiredness
Tender, swollen breasts. Your nipples might also stick out
Upset stomach with or without throwing up (morning sickness)
Cravings or distaste for certain foods
Mood swings
Constipation (trouble having bowel movements)
Need to pass urine more often
Headache
Heartburn
Weight gain or loss
As your body changes, you might need to make changes to your daily routine, such as going to bed earlier or eating frequent, small meals. Fortunately, most of these discomforts will go away as your pregnancy progresses. And some women might not feel any discomfort at all! If you have been pregnant before, you might feel differently this time around. Just as each woman is different, so is each pregnancy.
Second trimester (week 13– 28)
Most women find the second trimester of pregnancy easier than the first. But it is just as important to stay informed about your pregnancy during these months.
You might notice that symptoms like nausea and fatigue are going away. But other new, more noticeable changes to your body are now happening. Your abdomen will expand as the baby continues to grow. And before this trimester is over, you will feel your baby beginning to move!
As your body changes to make room for your growing baby, you may have:
Body aches, such as back, abdomen, groin, or thigh pain
Stretch marks on your abdomen, breasts, thighs, or buttocks
Darkening of the skin around your nipples
A line on the skin running from belly button to pubic hairline
Patches of darker skin, usually over the cheeks, forehead, nose, or upper lip. Patches often match on both sides of the face. This is sometimes called the mask of pregnancy.
Numb or tingling hands, called carpal tunnel syndrome
Itching on the abdomen, palms, and soles of the feet. (Call your doctor if you have nausea, loss of appetite, vomiting, jaundice or fatigue combined with itching. These can be signs of a serious liver problem.)
Swelling of the ankles, fingers, and face. (If you notice any sudden or extreme swelling or if you gain a lot of weight really quickly, call your doctor right away. This could be a sign of preeclampsia.)
Third trimester (week 29–40)
You're in the home stretch! Some of the same discomforts you had in your second trimester will continue. Plus, many women find breathing difficult and notice they have to go to the bathroom even more often. This is because the baby is getting bigger and it is putting more pressure on your organs. Don't worry, your baby is fine and these problems will lessen once you give birth.
Some new body changes you might notice in the third trimester include:
Shortness of breath
Heartburn
Swelling of the ankles, fingers, and face. (If you notice any sudden or extreme swelling or if you gain a lot of weight really quickly, call your doctor right away. This could be a sign of preeclampsia.)
Tender breasts, which may leak a watery pre-milk called colostrum (kuh-LOSS-struhm)
Your belly button may stick out
Trouble sleeping
The baby "dropping", or moving lower in your abdomen
Contractions, which can be a sign of real or false labor
As you near your due date, your cervix becomes thinner and softer (called effacing). This is a normal, natural process that helps the birth canal (vagina) to open during the birthing process. Your doctor will check your progress with a vaginal exam as you near your due date. Get excited — the final countdown has begun!
https://www.womenshealth.gov/pregnancy/youre-pregnant-now-what/stages-pregnancy