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Trimester 1

3 Weeks Pregnant

During week 3, 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
Your baby is the size of a vanilla bean seed
0.1 cm
Length
Less than 1 g
Weight
Week 1Week 13 - End of Trimester 1Week 27Week 42

Baby's Development This Week

During week 3, 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 fertilized egg (zygote) divides rapidly as it travels to the uterus.
  • By mid-week, the blastocyst implants into the uterine lining.
  • The placenta begins forming from the outer cells of the blastocyst.
  • The inner cell mass will become the embryo.

Your Symptoms at Week 3

You are still in the early stages of your journey at week 3. 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.

Implantation spotting
Light spotting is normal; use a panty liner. (mild)
Mild cramping
Rest and use a warm compress. (mild)
Slight fatigue
Get extra sleep when possible. (mild)

When to Call Your Doctor

  • Heavy bleeding (more than spotting)
  • Severe cramping or one-sided pain (could indicate ectopic pregnancy)
  • High fever

Week 3 Checklist

  • Continue prenatal vitamins (essential)
  • Avoid alcohol, smoking, and recreational drugs (essential)
  • Eat folate-rich foods (leafy greens, beans, citrus) (recommended)
  • Get 7-9 hours of sleep per night (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.