The First Trimester: Changes In Mom And Baby

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Some of the changes brought on by pregnancy are quite pleasant. Who would complain if they had glowing skin and warm toes? However, some changes are not as pleasant, like nausea and feeling tired all the time.

This chart shows the changes you and your baby will go through during the first trimester (from the first day of your last menstrual period to 13 weeks).

Changes in mom

Changes in baby

0 to 4 weeks

  • Your body begins to provide for your baby.
  • Your breasts may feel tender (or you may not notice any changes at all).
  • You may know that your menstrual period is late.
  • Your baby is called an embryo and is about 0.6 cm (¼ inch) long or about the size of a grain of rice.
  • The embryo sticks to (implants in) the wall of your uterus.
  • The placenta, amniotic sac and fluid begin to form.
  • The early structures of the brain have started to form.

5 to 8 weeks

  • You have missed your menstrual period.
  • You may feel tired.
  • You may feel strong emotions.
  • You may feel sick to your stomach or vomit (this can happen any time of the day, not just first thing in the morning).
  • You might not feel like eating.
  • The embryo is about 2.5 cm (1 inch) long and weighs less than a grape.
  • The heart starts beating.
  • The head and brain are taking shape.
  • Internal organs are forming.
  • Teeth begin to develop.
  • Arm and leg buds are beginning to show.
  • The spine starts to show and bones begin growing.
  • The spinal cord starts to develop nerve connections (synapses) that will allow your baby to move his limbs and fingers, hiccup, stretch and yawn.

9 to 13 weeks

  • You may be able to feel the top of your uterus, just above your pubic bone (it’s about the size of an orange).
  • You may notice changes to your skin and hair (e.g., skin problems may clear up or you may develop a rash).
  • You may feel sick (this can happen any time of the day, not just first thing in the morning).
  • You might not feel like eating, and you may vomit.
  • You might crave certain foods.
  • You might crave other things, like chalk or dirt (this is called pica—talk to your health care provider).
  • You may have constipation.
  • You may have yellow or white discharge from your vagina (this is normal).
  • You may have slight bleeding from your vagina (more common in women who have already had a baby). A little bleeding can happen; a lot of bleeding, or continued bleeding, needs to be checked.
  • Your gums may look redder than usual. They may be swollen, tender to touch and bleed easily.
  • You may feel tired often.
  • Your emotions may quickly change, from happy one moment to weepy the next.
  • Your baby, now called a fetus, is about 7.6 cm (3 inches) long and weighs about as much as a tube of lipstick.
  • The eyes, ears and nose have formed.
  • The mouth has formed, with lips, tongue and tooth buds.
  • The hands, fingers and fingerprints, knees, ankles and toes have formed.
  • The sex organs (male or female) have formed.
  • Your baby has started to kick (you can’t feel it yet).
  • Your baby sucks his thumb and makes breathing motions.
  • At around 12 weeks, you may be able to hear your baby’s heartbeat through a fetal Doppler.
  • Your baby’s basic brain cells (neurons) are developing very quickly, becoming more organized and are starting to connect to each other.

© Lennart Nilsson/SCANPIX

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