What to expect the first trimester of pregnancy

From what's going on your body and your baby's development to whether it's OK to drink caffeine

By: Peter Klemin, MD .

First trimester, what you need to know
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When is the first prenatal visit?

Most first visits happen between 10 and 12 weeks, but could be sooner in high-risk situations. If you are experiencing problems such as severe morning sickness, bleeding, pain or have complex medical problems that could affect your pregnancy, you may need to be seen sooner.

What symptoms can be expected during this time?

Common symptoms include:

  • Nausea and vomiting, any time of day, not just morning sickness
  • Fatigue
  • Bloating
  • Constipation
  • Breast tenderness
  • Heartburn
  • Cramping
  • Vaginal bleeding/spotting occurs with relative frequency (must be evaluated)
  • Headaches

How long will the fatigue last?

For most women, the extreme fatigue of the first trimester is soon forgotten with the glow and boost in energy that comes with the second trimester. So if it seems like all you’re doing these first few weeks is lying around, dozing, or napping, don’t worry. It’s normal. Although fatigue often returns in the third trimester because of disrupted sleep and increasing discomforts, this too will pass in time.

What can you do to feel better?

  • Eating small, frequent, healthy meals can keep you going and can also help with nausea.
  • If you’re at work and fighting back drooping eyelids, try some stretches or deep breathing exercises. Or get up and walk around the office or take a break outside.
  • When you can, go for a brisk walk around the block. A little exercise can energize you and may help you rest better when you do get to sleep.
  • Adapt your sleep habits. Take naps, if possible, during the day. You may also want to try going to bed earlier.
  • Drink enough fluids during the day and little several hours before bedtime. This may help you avoid having to get up to urinate during the night.

What should you avoid?

Squelch the urge to drink coffee or other caffeinated drinks to stay alert, as the caffeine really isn’t good for your developing baby. Instead, drink plenty of water.

It’s easy to feel guilty about not being able to do everything like you’re used to. It’s OK to pamper yourself. By reducing any extra job or social commitments during these first few weeks, you can be as productive as possible in your regular responsibilities.

What changes in the mother’s body?

Aside from some of the symptoms mentioned above, here are a few additional changes:

  • Heart rate may increase
  • Some women, even early on, notice decreased exercise/activity tolerance
  • Respiratory rate may increase
  • Some women notice hair and nail changes such as thicker hair and stronger nails
  • Some women develop acne
  • Breast enlargement begins for some

What fetal development is happening?

  • The majority of the first trimester is the embryonic stage. It begins with the fertilized egg implants in the uterus and develops the blood supply (placenta).
  • The embryo is experiencing basic growth, with the beginning development of the brain, spinal cord, heart and gastrointestinal tract.
  • By weeks 4 and 5, arm and leg buds are visible. The heart is now beating at a steady rhythm. The early structures of the eyes and ears are forming.
  • Week 6 begins formation of lungs, jaw, nose and palate. The hand and feet buds have webbed structures that will become the fingers and toes. The brain is continuing to form.
  • At 7 weeks, every essential organ has begun to form. The hair and nipple follicles are forming, and the eyelids and tongue have begun formation. The elbows and toes are more visible.
  • In week 8, the ears are continuing to form externally and internally. Everything that is present in an adult human is now present in the small embryo. The bones are beginning to form, and muscles can contract. Facial features continue to mature, and the eyelids are now more developed.
  • At 10 weeks, the genitalia have clearly formed into male or female, but still cannot be seen clearly on an ultrasound. The eyelids close and will not reopen until the 28th week of pregnancy. The fetus can make a fist, and the buds for baby teeth appear. The head is nearly half the size of the entire fetus.

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