Pregnancy Guide

Photos originally published by BabyCenter, L.L.C.


First Trimester

Week 1:
Fetal Developments:
• Conception has not yet occurred.

Maternal Changes:
• Menstrual period has just started
• If you have not yet begun to use healthy eating and living habits, start now.

Week 2:
Fetal Developments:
• Still nothing

Maternal Changes:
• Eggs are ripening
• Uterus is replenishing its lining with new vascularized tissue

Week 3:
Fetal Developments:
• Conception occurs by the uniting of the male sperm fertilizing the female egg in one of the woman’s fallopian tubes

Maternal Changes:
• A ripened egg is released into one of your fallopian tubes

Week 4:
Fetal Developments:
• The blastocyte, which forms the placenta and the baby, implants into the lining of the uterus

Maternal Changes:
• Fatigue
• Breast soreness
• Mood swings

Week 5:
Fetal Developments:
• Has 3 layers
      • Ectoderm (top layer)- the neural tube, which will grow into the nervous system, is formed
      • Mesoderm (middle layer)- the circulatory system is presently formed here
      • Endoderm (inner layer)- the pancreas, liver, intestines, and bladder are formed from the endoderm tube

Maternal Changes:
• Increased frequency of urination
• Swollen breasts (from enlarging mammary glands)
• Breast tenderness
• Hunger
• Nausea

Week 6:
Fetal Developments:
• 1/17 of an inch long
• Now considered an embryo
• Umbilical cord develops
• Ears, eyes, and opening for the mouth begin to form
• 1st heartbeats
• Heart begins pumping blood
• Most organs have begun forming
• Buds, that will eventually become the arms and legs, form on the body

Maternal Changes:
• Morning sickness
• Avoid substances that could harm the baby
      • i.e. alcohol, drugs, and treatments with harsh chemicals (perms, hair coloring, and manicures)

Week 7:
Fetal Developments:
• 1/3 of an inch long
• Arms and legs continue to develop
• Fingers and toes have not yet formed
• Eyes, brain, nostrils, bronchi, intestines, and pancreas continue to grow

Maternal Changes:
• Symptoms from Week 6
• Slight weight change
      •Loss of a few pounds
      •Gain of a few pounds
• You are still not “showing”

Week 8:
Fetal Developments:
• Elbows and fingers begin to develop
• The leg buds start to form feet with notches for the toes
• Ears, eyes, and tip of the nose appear making the face more defined
• Teeth develop under the gums
• Intestines form in the umbilical cord

Maternal Changes:
• Waistline may be slightly expanding as your uterus is approximately the size of an orange
• Because of changing hormones, you may experience oily skin and acne

Week 9:
Fetal Developments:
• Bones and cartilage begin to form
• Eye continues to form
• Tongue begins to develop
• Intestines move from umbilical cord to abdomen
• Fingers and thumb form but are short and webbed

Maternal Changes:
• Breasts are fuller and more sensitive
• Waistline is growing
• Heartburn
• Indigestion

Week 10:
Fetal Developments:
• Baby begins moving
• Most of the joints are now formed

Maternal Changes:
• Morning sickness may abate
• Moodiness
• Veins might become more prominent due to increased blood flow

Week 11:
Fetal Developments:
• The baby (now considered a fetus) will grow from approximately one inch to approximately two inches
• Eyelids fuse shut
• Irises begin to develop
• Placenta starts to function as blood is circulated between the baby and the uterus

Maternal Changes:
• Appetite may be better
• Uterus is approximately the size of a grapefruit

Week 12:
Fetal Developments:
• Fingers and toes separate
• Hair and nails begin to grow
• Genitals begin forming
• As the baby’s kidneys excrete urine, amniotic fluid accumulates
• Peristalsis begins in the intestines

Maternal Changes:
• Because the uterus moves up and forward, less pressure will be on your bladder, which means you will most likely have less trips to the bathroom
• Fatigue may subside
• Headaches and light-headedness result from an increased blood volume

Second Trimester

Week 13:
Fetal Developments:
• Eyes move closer together from the sides of the head
• Ears move to a typical position of the head
• Vocal cords begin forming
• Liver starts to secrete bile
• Pancreas begins producing insulin
• Intestines migrate farther into the baby’s body

Maternal Changes:
• Abdominal achiness from the stretching uterus
• Round ligament pain from the stretching of the ligaments that keep the uterus in place

Week 14:
Fetal Developments:
• 3 1/2 inches long
• 1-2 ounces
• Inhaling and exhaling movements are practiced
• Face continues to develop as eyes and ears move and develop
• Neck elongates
• The baby’s chin no loner rests on his/her chest
• The functioning of the hands improves
• Placenta nourishes the baby

Maternal Changes:
• Decrease of early pregnancy symptoms
• Constipation
• Changing breasts
• Dilated veins in the chest/breast area
• Darkened and growing areolas

Week 15:
Fetal Developments:
• The skin is thin and transparent
• The bones are getting harder
• Lanugo covers the baby’s body

Maternal Changes:
• Your uterus is about 3-4 inches below your navel

Week 16:
Fetal Developments:
• Fetal movement may be felt by the mother, due to the hardening of the baby’s bones
• Legs are longer than the arms
• Fingernails and toenails are growing

Maternal Changes:
• Stuffy nose
• Nosebleeds
• Abdominal pain and achiness

Week 17:
Fetal Developments:
• Reflexes are now in place
• Fat accumulates under the skin
• Baby’s heart pumps about 25 quarts of blood per day

Maternal Changes:
• Your uterus is approximately 1 1/2-2 inches below your navel
• At this point, the average weight gain for the mother is 5-10 pounds

Week 18:
Fetal Developments:
• Around half a pound
• On the fingertips and toes, pads are formed
• Rather than looking to the sides, the eyes begin to look forward
• The baby’s first bowel movement, meconium, is gathering in the bowel

Maternal Changes:
• Your uterus is right under your navel

Week 19:
Fetal Developments:
• Vernix Caseosa, which is a cheesy substance that protects the baby’s skin from the aquatic environment of the womb, forms on the skin

Maternal Changes:
• Skin changes
      • Blotchy patches on chin, cheeks, nose, and forehead
      • Itchy skin
      • Dry and flaky skin
      • Rashes
      • Stretch marks

Week 20:
Fetal Developments:
• If a girl, the baby’s uterus begins developing
• Hair on the scalp starts to grow
• The baby is asleep and awake in the womb for the same amounts as it will once born

Maternal Changes:
• Your uterus now reaches your navel
• The line between your belly button and pubic hair, linea nigra, has now darkened

Week 21:
Fetal Developments:
• The baby’s legs are continuing to grow to their normal proportions
• His/her heart grows stronger

Maternal Changes:
• At this point, the average weight gain for the mother is between 10 and 15 pounds
• Your uterus is approximately 1/2 inch above your belly button
• Swelling in the ankles and feet

Week 22:
Fetal Developments:
• Weight is close to a pound
• Brain undergoes rapid growth
• Eyelids and eyebrows are now formed
• If a boy, his testes begin to descend to the scrotum from the pelvis

Maternal Changes:
• Weight will steadily be gained as your baby gains weight
• Your uterus is about an inch above your belly button
• Back pain/strain

Week 23:
Fetal Developments:
• Bones of middle ear are hardening
• Baby’s body is becoming better proportioned

Maternal Changes:
• Your uterus is approximately 1 1/2 inches above your uterus
• You may feel movement from the baby
• Extreme mood swings

Week 24:
Fetal Developments:
• Because the baby’s body is filling out at this stage, about 6 ounces will be gained
      •This weight will come from muscle, bone mass, and growing tissues and organs

Maternal Changes:
• Your uterus is somewhere between 1 1/2-2 inches above the navel

Week 25:
Fetal Developments:
• The various structures of the spine begin to form
• Nostrils start opening
• The lungs’ blood vessels begin to develop

Maternal Changes:
• The pressure of the uterus may cause shooting pains in your legs and lower back

Week 26:
Fetal Developments:
• Approximately two pounds
• From head to rump, about nine inches long
• Alveolar air sacs begin to develop, as well as the surfactant that covers the lining of these air sacs
• Brain wave activity begins for the auditory and visual systems

Maternal Changes:
• Your uterus is approximately 2 1/2 inches above your navel
• “Braxton Hicks” Contractions

Week 27:
Fetal Developments:
• Brain and lungs continue to grow and develop
• Retinas start forming
• Eyelids start the process of opening
• 1/2 an inch of growth

Maternal Changes:
• Shortness of breath

Third Trimester

Week 28:
Fetal Developments:
• Eyelashes have formed
• Scalp hair continues to grow
• Eyes are formed
• Eyelids open
• Muscle mass grows
• Baby’s body is filling out
• Lungs now have the capability to breathe air

Maternal Changes:
• Your uterus is approximately 3 inches above your navel
• At this point, the mother’s average weight gain is somewhere between 17 and 24 pounds

Week 29:
Fetal Developments:
• Primitive thinking and body temperature control are now under the control of the brain
• Fat accumulates under the skin
• The baby’s head is in proper proportion with the rest of its body
• Eyes have the ability to move in the sockets
• Light, smell, taste, and sound are sensed

Maternal Changes:
• Itchy skin
• Hemorrhoids
• Leg cramps
• Achy muscles
• Continued shortness of breath
• Indigestion
• Heartburn

Week 30:
Fetal Developments:
• About 3 pounds
• Disappearance of lanugo
• Bone marrow controls red blood cell production
• Eyelids open and close
• Growth of toenails

Maternal Changes:
• Trouble sleeping

Week 31:
Fetal Developments:
• Brain undergoes rapid development

Maternal Changes:
• Aching abdomen
• Stretching uterus
• Your uterus is approximately 4 1/2 inches above your navel

Week 32:
Fetal Developments:
• Weighs 4 pounds
• Baby uses all five senses
• Hair on head continues to grow
• Toenails are fully formed

Maternal Changes:
• Your uterus is around 5 inches above your navel
• Heartburn
• Indigestion
• Shortness of breath
• Constipation

Week 33:
Fetal Developments:
• amniotic fluid is at its highest level for the pregnancy
• rapid brain growth causes the baby’s head to grow 3/8 of an inch
• the accumulation of fat under the skin changes the skin color from red to pink

Maternal Changes:
• You will start gaining a pound per week
• Mild edema

Week 34:
Fetal Developments:
• Developing immunities
• Eyes open when the baby is awake and close when the baby is asleep

Maternal Changes:
• Intensified Braxton Hicks Contractions

Week 35:
Fetal Developments:
• Approximately 5 1/2 pounds
• Arms and legs plump
• If a boy, the testes have fully descended
• Less room for the baby to move around in the uterus

Maternal Changes:

Week 36:
Fetal Developments:
• Fat increases on the elbows, knees, wrists, and neck
• Rigid gums

Maternal Changes:
• Average weight gain for the mother is somewhere between 25 and 30 pounds

Week 37:
Fetal Developments:
• Approximately 6 1/2 pounds
• Develops firm grasp
• Begins turning toward light

Maternal Changes:
• Increase in vaginal discharge and cervical mucus

Week 38:
Fetal Developments:
• An ounce per day might be gained
• Meconium is accumulating in the intestines
• The head and abdomen’s circumferences are about the same

Maternal Changes:
• False labor

Week 39:
Fetal Developments:
• Lungs are maturing
• Lung surfactant production increases
• Average weight is 7 pounds

Maternal Changes:
• Easier to breathe
• Increased frequency of urination
• Your uterus is 6 1/2 to 8 inches above your belly button

Week 40:
Fetal Developments:
• Approximately 7 1/2 pounds and 20 inches long
• Most of the Vernix Caseosa is gone
• Chest sticks out
• Baby’s body is 15% fat

Maternal Changes:
• Possible cervix changes to prepare for labor