The 40 weeks of pregnancy often are grouped into three trimesters. Each trimester lasts about 3 months:

First Trimester(1-3 months):

• Eat frequent and smaller meals 
• Stay active and pursue moderate exercises. 
• Stay hydrated and avoid stressful activities.
• Quit smoking, drinking, and cut down on consumption of caffeine
• Get relief from pregnancy sickness
• Start doing your pelvic floor exercises
• Check before taking any medications

Contact Doctor if

• Heavy vaginal bleeding 
• Severe pain in the abdomen 
• Burning sensation when you urinate 
• Fever over 101 degrees
• Abnormal swelling of arms and legs

Second Trimester(4- 7 months):

• Increase your calorie consumption to 2200 calories per day.
• Drink plenty of water.
• Engage in mild exercise and relaxation techniques.
• Keep your leg elevated in case of swelling.
• Take warm baths to relieve body aches.
• Sleep on your left side with some support for your belly for better sleep
• Think about your maternity leave
• Avoid sports or any activities that carry a high risk of falling or trauma to the abdomen.
• Track your weight gain
• Try a relaxation technique

Contact Doctor if:

• Sudden weight gains and increased edema.   
• Itchy skin followed by nausea, fatigue, jaundice, and loss of appetite.
• Extreme thirst Frequent and copious urination. 
• Vision changes
• Vaginal bleeding
• High fever over 101 degrees 
• Severe pain in the abdomen

Third Trimester(7-9 months):

• Increase calorie consumption to 2400 calories each day. 
• Get as much rest as you can. 
• Use a pregnancy pillow for maximum support when you sleep. 
• Stay hydrated
• Wear compression socks to relieve leg pain
• Educate yourself about labor and delivery. 
• Be aware of your baby's movement
• Get to know your contractions

Contact Doctor if:

• A stringy mucus-like discharge that is pink or brown in color from the vagina 
• Longer and more prominent contractions
• Water breaking 
• Vaginal bleeding 
• Headache or any visions changes
• High Fever over 101 degrees

References: https://www.babydestination.com/pregnancy-stages-care-tips-trimester-by-trimester 

https://www.babycentre.co.uk/a1051123/first-trimester-your-essential-pregnancy-to-do-list 

https://www.healthline.com/health/pregnancy/calendar#third-trimester