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Trimester 1

13 Weeks Pregnant

During week 13, your baby is undergoing rapid organogenesis. Every day, millions of new cells are forming the foundations of the brain, heart, and limbs. They are safely tucked away in the amniotic sac, receiving all their nutrition through the developing umbilical cord.

8 min read Medically Reviewed Updated 2024-05-01
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Your baby is the size of a Peapod
7.4 cm
Length
23 g
Weight
Week 1Week 13 - End of Trimester 1Week 27Week 42

Baby's Development This Week

During week 13, your baby is undergoing rapid organogenesis. Every day, millions of new cells are forming the foundations of the brain, heart, and limbs. They are safely tucked away in the amniotic sac, receiving all their nutrition through the developing umbilical cord.

  • The vocal cords are forming.
  • Intestines move from the umbilical cord into the abdomen.
  • The fetus has unique fingerprints.
  • The head is about one-third the body's total length.
  • The fetus can make facial expressions.
  • About 7.4cm — the size of a peach.

Your Symptoms at Week 13

You are still in the early stages of your journey at week 13. Your body is working overtime to produce the hormones needed to support the pregnancy, which can lead to symptoms like fatigue and nausea. It's important to prioritize rest and stay hydrated during this demanding time.

Increased energy
Take advantage of the energy boost! (mild)
Round ligament pain
Stretch gently; avoid sudden movements. (mild)
Visible veins
Normal — your blood volume is significantly higher. (mild)
Constipation
Eat fiber-rich foods, drink water, and stay active. (moderate)
Occasional headaches
Stay hydrated and rest; acetaminophen is safe. (mild)

When to Call Your Doctor

  • Regular cramping or contractions
  • Bleeding
  • Fluid leaking from the vagina
  • High fever

Week 13 Checklist

  • Celebrate entering the second trimester! (optional)
  • Start sleeping on your side (left is ideal) (recommended)
  • Begin applying stretch mark cream or oil (optional)
  • Research second-trimester screening tests (recommended)
  • Continue moderate exercise (recommended)

Frequently Asked Questions

Medical Disclaimer: This content is for informational purposes only and is not a substitute for professional medical advice. Always consult your healthcare provider for personalized guidance about your pregnancy.