Pregnancy Week-By-Week Guide: The First Trimester

The First Trimester: What To Expect?

Weeks 1 and 2

Baby: Your baby is still just a glimmer in your eye. It’s difficult to know exactly when conception occurred, so doctors calculate your due date from the beginning of your last menstrual cycle. That’s right – for calculation purposes, you’re “pregnant” before you even conceive!  your already weeks into the first trimester!

Mum-to-be: At the beginning of your period, about 20 eggs called ova occupy fluid-filled sacs called follicles. If you typically have your period every 28 days, then about 14 days later, you ovulate: One of these follicles releases an egg, and it travels down your fallopian tube where it awaits fertilisation. This time — 14 days after your period started and a day or so longer — is when you’re the most fertile. If you want to get pregnant, this is the best time to try. Once the egg is fertilised, it moves into the uterus.

Week 3

Baby: Congratulations! If your egg and your partner’s sperm have joined successfully, your embryo is really there, although it’s very small — about the size of the head of a pin. It doesn’t look like a fetus or baby; it’s just a group of about 100 cells multiplying and growing rapidly. The outer layer of cells will become the placenta, and the inner layer will become the embryo.

Mum-to-be: You won’t notice any changes in your body at this point. Remember, you haven’t even missed your period yet.

Week 4

Baby: Now that your egg is fertilised, it burrows into the lining of your uterus. This is called implantation.

Mum-to-be: You’re probably expecting your period this week, and if it doesn’t occur, it might be one of the first signs that you’re pregnant. You may also notice light spotting as the embryo implants itself in your uterus. You might not feel any different yet, but the amniotic cavity, which will be filled with fluid, and the placenta, which will bring oxygen and nutrients to nourish your baby, are forming in your uterus.

Whats happening at the end of week 4 of the first trimester? 

The First Trimester

The fertilised egg grows, and a water-tight sac forms around it, gradually filling with fluid. This is called the amniotic sac, and it helps cushion the growing embryo.

The placenta also develops. It is a round, flat organ that transfers nutrients from you to the baby and transfers baby’s wastes.

A primitive face takes form with large dark circles for eyes. The mouth, lower jaw, and throat are developing. Blood cells are taking shape, and circulation will begin.

Week 5

Baby: Your baby is still tiny, but its heart, brain, spinal cord, muscle, and bones are beginning to develop. The placenta, which nourishes your baby, and the amniotic sac, which provides a warm and safe environment where your baby can move easily, are still forming, too. The umbilical cord forms and connects your baby to your blood supply.

Mum-to-be: You might suspect by now that you’re pregnant. You may also notice some early symptoms of pregnancy:

  • Feeling nauseous (called morning sickness, although it can happen at any time of day or night)
  • Tingling or soreness in your breasts and darkening of your nipples
  • Needing to urinate more often
  • Feeling more tired than usual

Week 6

Baby: Your baby is shaped like a tadpole, and it’s about the size of a BB pellet. The eyes and limb buds are forming. During an ultrasound, your doctor may be able to hear a heartbeat. Between days 17 and 56 is a vulnerable time, because that’s when the baby is most susceptible to anything that can affect normal growth.

Mum-to-be: You may have gained a few pounds by now. Or if you’re having morning sickness you may have lost weight — that’s normal, too. You may start noticing some changes in your body: clothes getting a little tighter around your waist, fuller legs and breasts. With a pelvic exam, your doctor will notice a change in the size of your uterus.

Week 7

Baby: Your baby is growing. Limb buds appear that will grow into hands and feet. Many parts continue to develop: heart, lungs, intestines, appendix, brain, spinal cord, nostrils, mouth, and eyes.

Mum-to-be: You’re still not “showing,” but by now you’re really feeling the changes in your body. You may still have morning sickness, and your breasts probably still feel tingly and tender.

Week 8

Baby: Your baby is now about in its sixth week of development. It’s a big week for growth. Eyelid folds and ears are forming. Your baby develops little webbed fingers and toes and can even swim around in your womb.

Mum-to-be: Your blood volume is increasing, and your heart is pumping 50% more blood per minute for your baby. Common symptoms for this week are moodiness and queasiness from certain smells.

What Takes Place At The End Of This Period?

Your baby’s facial features continue to develop. Each ear begins as a little fold of skin at the side of the head. Tiny buds that eventually grow into arms and legs are forming. So are fingers and toes.

9 Weeks Pregnant

Baby: Your baby is about the size of a peanut. The head is more erect, and the neck is more developed. During an ultrasound, you might see how your baby moves, even though you can’t feel it yet.

Mum-to-be: Your uterus is continuing to grow, and you may notice your waistline thickening. Unless you tell people your special news, however, your pregnancy still won’t be noticeable to others. You shouldn’t have gained much weight yet, especially if you’re having food aversions, cravings, heartburn, indigestion, nausea, or bloating.

10 Weeks Pregnant

Baby: Your baby is still small but looks and acts like a baby. Arms and legs are longer and can bend at the elbows and knees.

Mum-to-be: Once the size of your fist, your uterus is now the size of a grapefruit. You still probably don’t show much, but you may feel more comfortable in looser clothes. You may continue to feel tired and moody, but take heart: These symptoms shouldn’t last too much longer. The first trimester is nearly over!

11 Weeks Pregnant

Baby: It’s another big growth week. When your doctor uses a Doppler stethoscope now, she can hear the rapid “swooshing” noises of the heartbeat. Your baby’s genitals are developing, but the sex can’t be determined yet by ultrasound.

Mum-to-be: Pregnancy hormones show their good and bad effects. You may notice that your hair, fingernails, and toenails are growing faster. But you may also notice oily skin and acne.

12 Weeks Pregnant

Baby: All parts of your baby are developing, from tooth buds to toenails. Your baby will keep developing and getting larger and stronger for the rest of your pregnancy. By the end of this week, the chance of miscarriage drops considerably.

Mum-to-be: You’ll feel more energetic for the next few weeks. The typical weight gain by now is from 1.5 to 5 pounds. Fathers-to-be might also experience pregnancy symptoms, called couvade, or “hatching,” during the third month and at delivery, including nausea, abdominal pain, appetite changes, and weight gain.

What’s Happening Inside You At The End Of The First Trimester?

By the end of the first trimester, your baby is fully formed, with arms, hands, fingers, feet, and toes. Little hands can open and close. Fingernails and toenails are beginning to develop, and the external ears are formed. Teeth are starting to form. Your baby’s reproductive organs also develop, but the baby’s sex is difficult to distinguish on ultrasound. The circulatory and urinary systems are working, and the liver produces bile.

The First Trimester

 

Below you can view the second and third trimester pregnancy guides.

The Second Trimester: Week-by-week guide

The Third Trimester: Week-by-week guide