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Pregnancy week by week

A pregnancy is generally measured in units called trimesters, divided into the three phases of pregnancy. These trimesters each last roughly 13 weeks, and a full term pregnancy is considered to be between 38 and 42 weeks long. Any baby born between these weeks is considered as an “on time” delivery.

Although your doctor will give you a due date, keep in mind that this date is not carved in stone. Your baby could decide to enter the world two weeks before or two weeks after the predicted due date, and still be considered “full term”.

In some cases, your baby may be born even earlier, which is considered a premature birth. Depending on how early your baby arrives will determine the level of care required to bring your baby to a state of health. Many years ago, premature babies had little chance of survival. However, with today’s innovative technology, babies that weigh only a few ounces at birth fight to live, and they do.

Pregnancy calendar: week by week

Enter the date of the first day of your last menstrual period (LMP) and we’ll calculate a week-by-week timeline for you.

Here is a Week by week pregnancy calendar showing different stages of your body and baby development:

Pregnancy Calendar Week 1-13 (First Trimester)

WEEK	YOU AND YOUR BODY	YOUR BABY
One	Sperm penetrates the egg, causing fertilization	Gender of the fetus is already determined
Two	Embryo has attached to the placental wall of the uterus	Embryo begins development, measuring a mere .006 of an inch long
Three	Early symptoms of pregnancy (morning sickness, breast tenderness, fatigue) begin	Central nervous system and cardiovascular system are developing, including blood cells and the heart
Four	No significant changes	Limbs begin to develop as small stumps, ears begin to form, and embryo now measures around .04 inches long
Five	Nausea may become more severe	Embryo’s head is the largest feature due to rapid brain growth, and the embryo is now between 2 and 3 inches long
Six	Breasts will start to enlarge and become more tender to touch	Fetus’ heart is now beating. An ultrasound or sonogram can detect the heart and tiny body although movement is not yet visible
Seven	No significant changes	Mouth, fingers, and toes are becoming more distinct, eyelids have formed, and movement is more detectable via ultrasound or sonogram
Eight	Sciatic nerve may cause some discomfort in the legs	Blood vessels are forming, fetus is taking on a more baby-like appearance with a rounded head and defined organs, and the fetus now measures 1 to 1.2 inches long, which is 10,000 times the size it was at conception
Nine	Waist will begin to thicken, and the uterus has grown to the size of a softball or grapefruit	Fetus has straightened, fingers and toes are quite defined, and movements, although small, can now be felt somewhat like small bubbles
Ten	Weight will continue to increase and some women will start to show while many still do not look pregnant to other people	Fetus now has very distinct human features and measures up to 1.5 inches in length
Eleven	Hair and nails generally become stronger because of prenatal vitamins and the uterus is swollen and starting to become visible	Major organs are formed and developing and the fetus is around 1.5 to 2.5 inches long. At this point in the pregnancy, risks of genetic problems are greatly reduced. Typically, another sonogram will be performed.
Twelve	Weight gain is becoming noticeable for the first time, especially in your hips, and a dark line often develops down the abdomen, called Linea Nigra	Fetus’ chest rises and falls as though breathing as muscles learn how to work, heartbeat can easily be detected with ultrasound, and the fetus can suck its thumb and swallow
Thirteen	Stretch marks may appear on the abdomen, buttocks, and your breasts	Fetus now has organs that have taken over the production of blood cells, movement is occurring as the fetus flexes its muscles, bones and teeth are developed, and fetus measures up to 3 inches long

Pregnancy Calendar Week 14-26 (Second Trimester)

WEEK	YOU AND YOUR BODY	YOUR BABY
Fourteen	May develop moles, which you never had before or existing moles may increase in size	Fetus is continuing its growth process and now weighs around 1 pound
Fifteen	Fetus will begin to respond to stimulus, often moving when pressed against	Fetus is now covered with a fine coat of protective hair called Lanugo”, fetus can hear your heartbeat and the sounds of your stomach
Sixteen	Fetus will start moving more frequently	Depending on age or medical history, your doctor may recommend an Amniocentesis test to rule out certain abnormalities such as Down Syndrome
Seventeen	You will continue gaining weight, have a good level of energy, and continue to feel the fetus move	Fetus’ arms and legs are now developed, it can distinguish between salty and sweet tastes, is now weights around 6.5 ounces
Eighteen	Lower back pain and nasal congestion are common around this time	Fetus often develops hiccups that can easily be felt, starts responding to external noises, and weight is increasing rapidly, up to 8.6 ounces
Nineteen	Mild vertigo, or dizzy spells, is common. Stand up slowly and in addition to your six small meals, add a few snacks into your diet such as crackers or fresh fruit	Fetus now has milk teeth, additionally baby teeth are developing under the surface of the gums, and the fetus is approximately 10 ounces
Twenty	You have now reached the HALFWAY point! Itching on the abdomen and breasts will begin, due to the stretching of the skin	Fetus is covered with Vernix, which is a greasy coating that protects its skin from the amniotic fluid
Twenty-One	Swelling and discomfort are common in the hands, legs, and feet	Fetus continues growing with more and more movement
Twenty-Two	Food cravings begin, which is normal. However, if you experience bizarre cravings, it could be due to a mineral deficiency so be sure to talk to your doctor	Fetus’ weight gain starts to stabilize while the size continues to increase, head and body begin to come into more normal proportion
Twenty-Three	Early uterine contractions will occasionally occur	Sexual organs are now fully developed and more aggressive movement occurs
Twenty-Four	Fetus’ heartbeat can easily be detected and since your unborn baby can hear and recognize your voice, talk to it in a soothing tone	Sleep patterns start to be defined and the fetus now weighs over 1 pound
Twenty-Five	Rib pain, leg cramps, and headaches are common as the fetus takes up more uterine space cramping your organs and causing discomfort	Brain cell development is rapid, bones are losing softness, fetus is now inhaling and exhaling as it prepares for birth
Twenty-Six	May experience increased lower back pain as the fetus’ weight pulls on the spine, sit down and put your feet up whenever possible	If the fetus were to be born at this time, chance are it could survive at its current weight of 2 pounds, brain and lung continue to develop and a small amount of fat is now forming on the fetus

pregnant expecting mom

Pregnancy Calendar Week 27-40 (Third Trimester)

WEEK	YOU AND YOUR BODY	YOUR BABY
Twenty-Seven	Start prenatal classes in preparation for childbirth	Fetus’ eyes are open and blinking, can sense light and dark through your abdomen, and is usually sucking the thumb or hand
Twenty-Eight	Make arrangements for other children and/or pets	Although the lungs are still weak, fetus could easily survive if born at this time, and fetus now weighs around 2 pounds
Twenty-Nine	Check off your list for baby equipment and clothing to ensure you have everything needed	Eyebrows, hair, and eyelashes have grown in
Thirty	Not as much kicking due to limited space	Fetus is now consuming most of the uterine space and to get comfortable, will cross its arms and legs while drawing itself up
Thirty-One	Watch for warning signs of Preeclampsia	Brain is growing rapidly, fetus will respond to pain and touch, and the skin is starting to smooth out
Thirty-Two	You will feel the fetus turning and rolling rather than kicking as it positions itself for birth	Fetus has twisted itself head down in preparation for delivery and weighs around 3.5 pounds (if fetus has not positioned itself head down, this is a Breach birth and generally requires a C-Section birth)
Thirty-Three	Heartburn can be significant and if horribly uncomfortable, consult your doctor	Fingernails have formed, lungs are almost completely developed, and the fetus is now inhaling and exhaling at a regular rate
Thirty-Four	Although the fetus is still gaining weight, your weight gain has slowed down	If the fetus is a male, the testicles have dropped, fetus is responding more to outside stimulus, and the weight is up to 4.5 pounds
Thirty-Five	Mood swings, fear, and bouts of crying are typical	Fetus is now approaching 5 pounds
Thirty-Six	Total weight gain is generally between 25 and 30 pounds	Central nervous system is reaching full maturity and toenails are now complete
Thirty-Seven	Doctor will perform a pelvic examination to check on the position of the fetus	Lanugo (soft, protective hair) begins to diminish
Thirty-Eight	A sense of depression and being overwhelmed is common as hormones fluctuate and you will start to feel a tugging low in your abdomen as the fetus drops	Body fat has developed under the skin to protect and insulate the fetus and weight is now around 6.5 pounds
Thirty-Nine	Discomfort from the weight gain is now quite evident with increased lower back pain	If fetus is born now, it would be considered as a “full-term” baby
Forty	Contractions will be felt, intensifying, as you get closer to delivery. If contractions do not begin, your doctor may want to check the progress to include the thinning of the cervical wall and position of the fetus	Fetus is generally head down, knees pulled up to check, waiting to make its entrance