What happens with your baby and your body each week of pregnancy — based on ACOG and NHS guidelines.
First Trimester (Weeks 1–13)
According to ACOG (American College of Obstetricians and Gynecologists), the first trimester begins from the first day of your last menstrual period. By week 4, the embryo implants in the uterus. By week 6, the heart begins to beat. By week 12, all major organs have formed.
Common Symptoms
Weeks 5–8: Morning sickness — affects 70–80% of pregnant women (ACOG)
Weeks 6–10: Pronounced fatigue due to high progesterone levels
Week 12: First ultrasound — confirms gestational age and number of fetuses
Second Trimester (Weeks 14–27)
According to the NHS, this is called the "golden period" of pregnancy. Nausea usually subsides and energy increases.
Week 16: The fetus begins to hear sounds — a study by Kisilevsky et al. (2009), Developmental Science showed the fetus responds to the mother's voice
Weeks 18–22: First fetal movements (quickening)
Week 20: Anomaly scan (anatomy scan) — checks organs, limbs, and development
Week 24: The fetus reaches "viability" — can survive outside the womb with intensive care
Third Trimester (Weeks 28–40)
According to the WHO, in the third trimester, the fetus gains about 200 grams per week.
Week 28: Eyes begin to open. Brain develops rapidly
Week 32: Bones harden but skull remains soft for delivery
Week 36: Fetus usually turns head-down (cephalic position)
Week 37: Considered "early term" — organs are nearly mature
Weeks 39–40: Full term — ideal time for delivery per ACOG
When to Contact Your Doctor
According to NICE (National Institute for Health and Care Excellence), contact your doctor immediately if you experience:
Kisilevsky BS et al. (2009). "Fetal sensitivity to properties of maternal speech." Developmental Science, 12(4), 550–556.
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When should you seek medical help?
If the child has a high temperature that does not go down, difficulty breathing, loss of consciousness, convulsions, signs of dehydration or other symptoms that concern you, do not rely only on the information in this article. Contact a doctor or emergency service immediately.
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Medical Disclaimer: This article is for informational purposes only and does not replace professional medical advice, diagnosis or treatment. Always consult your pediatrician or a qualified healthcare professional for any questions regarding your child's health. Never disregard professional medical advice or delay seeking it because of something you have read on SolKids.
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Caution: The information in this article is informative and educational in nature. It does not constitute medical advice, diagnosis or treatment and does not replace consultation with a doctor, pediatrician or other licensed health professionals. Any decision related to the health, development or well-being of the child should be made in consultation with a qualified professional. If the child shows worrying symptoms or is in an emergency situation, contact the emergency service immediately or go to the nearest health institution.
