The Average Length of Pregnancy (Gestational Age) is 280 days, or 40 weeks, from the first day of the woman’s last menstrual period. An estimated due date can be determined by two simple rules – (1) Add seven days to the first day of your last menstrual period (LMP) and then subtract three months. (2) the second way to estimate the due date can be determined on the first day of your last menstrual period.

A pregnancy is divided into trimesters: First Trimester, Second Trimester, and Third Trimester.

At this point, your baby looks like a tiny human being and is now called a fetus.

Baby Growth During the First Trimester

• Baby will be 7 to 10 cm long (3 to 4 inches) and weigh 28 grams (1 ounce).
• The eyes, ears, and nose start forming. 
• His heart is beating and functioning.
• Bones begin to form.
• The digestive tract and nervous system are beginning to form.
• The fetus can now move in the amniotic fluid.
• The arms, legs, fingers, and toes are forming (fingernails and toenails are forming).
• The sex of your baby is determined.
• Fetus’s Brain starts growing and the spine starts developing. 

Physical Changes in Your Body 

• Nausea with or without vomiting.
• May have mood swings.
• Now you will pass urine more often.
• Your Breast will be bigger, as it starts preparing the milk.
• Feeling Tired and heaviness in the body.
• Will Experience Heartburn and Constipation.
• Food cravings will start.
• Fatigue more.

Your baby might begin to seem more real and has functioning organs, nerves and muscles.

Baby Growth During the Second Trimester

• He/She will be about 36 cm long (14 inches) and weigh 1 kilogram (2 pounds).
• Bones are beginning to harden in your baby’s skeleton and the baby’s skin is getting thicker.
• Now he or she can open the eyes.
• The eyebrows and lashes appear.
• Baby’s neck has become more defined
• Your healthcare provider can hear your baby’s heartbeat.
• Baby’s Scalp hair pattern is forming and by the end of the second trimester, it will be visible in ultrasound. 
• Baby can roll and flip, he will be more active in the amniotic sac. Someone Pregnant Woman can feel their Baby’s Movements.
• Baby can suck his thumb and can have a hiccup.
• Your baby might begin to hear sounds.
• A white coating (vernix) begins to cover your baby’s body.
• The Baby teeth develop inside the gums.

Physical Changes in Your Body

• You may feel like fluttering and bubbles inside the womb.
• A little bit of Fluid may leak from your breasts.
• Acne Problems can be started in the second trimester of pregnancy.
• Will feel pressure in my legs and swollen veins.
• You may through low back pain coz of a growing belly in front. 
• Bleeding from Gums. 
• Might notice a sticky, clear, or white vaginal discharge. 

During The Third Trimester you Baby is well Developed. 

Baby Growth During the Third Trimester

• He or she will be about 51 cm long (20 inches) and weigh 3.5 kilograms (7.5 pounds).
• your baby can kick, stretch, and increase his movements. 
• He can open his eyes wide. 
• Now, he has good hair on his head.
• Baby’s brain, lungs, and other organs continue to develop.
• The baby responds to light and can hear the sounds.
• The sex organs are developed
• The baby may move into a head-down position, getting ready to be born.

Physical Changes in Your Body

• Stretch marks on your tummy and breasts.
• Braxton Hicks contractions – you may feel mild, irregular contractions as a slight tightness in your abdomen.
• Shortness of breath coz of extra weight
• Most common back pain and swollen legs.
• Burning feeling in your chest and throat.
• You may pass urine more often.
• Now you’re ready for labor and welcoming your newborn baby.