Week 5: The Heart Begins
Your baby's heart is starting to form and will begin beating this week! The neural tube, which becomes the brain and spinal cord, is also developing.
Medically reviewed by Samantha L. Fox, RN, BSN, MSN
Nursing Informaticist · United States Navy Nurse Corps · Last reviewed
Your baby is the size of a...
🫘 Sesame Seed!
👶 Baby Development
- ✓Heart begins to form and may start beating
- ✓Neural tube (future brain and spinal cord) develops
- ✓Arm and leg buds start to appear
- ✓Digestive system begins forming
- ✓Umbilical cord is developing
💊 Common Symptoms
- •Morning sickness may begin (nausea with or without vomiting)
- •Increased urination frequency
- •Food aversions or cravings
- •Heightened sense of smell
- •Continued breast tenderness
- •Fatigue and exhaustion
🩺Clinical Context — From a Nurse's View
By week 5, hCG should roughly double every 48-72 hours in a healthy early pregnancy. If your provider is drawing serial betas, that's the trajectory they're watching — not a single number. A slower rise doesn't automatically mean miscarriage, but it does mean closer follow-up. The embryonic heart starts forming this week and may begin a faint flicker on transvaginal ultrasound around 5w5d to 6w0d at roughly 90-110 BPM. If you scan this early and don't see cardiac activity, it usually just means timing was a few days off; the standard move is a repeat scan in 7-10 days, not panic. Nausea may begin this week, often worse on an empty stomach. Eat something small every 2-3 hours — even crackers — before the nausea peaks. The misnomer 'morning sickness' is unhelpful; for most people it's all-day. If you can't keep liquids down for more than 12 hours or you've lost more than 5% of your pre-pregnancy weight, that's hyperemesis territory and worth a call (ACOG, 2018).
Written by Samantha L. Fox, RN, BSN, MSN — Emergency Department nurse, US Navy Nurse Corps officer.
🚨 When to Call (or Go to the ER)
- !Heavy bleeding (more than a normal period) — ER
- !Severe one-sided pain or shoulder-tip pain — ER for ectopic workup
- !Vomiting more than 3-4 times a day with inability to keep fluids down for 12+ hours — call same day
- !Slowly-rising or falling hCG on serial labs — your provider will guide next steps
✅ Normal — Even If It Feels Worrying
- ✓Nausea that comes and goes throughout the day
- ✓Symptoms that feel stronger one day and milder the next
- ✓Mild cramps as the uterus starts to expand
- ✓Light brown spotting after a vaginal exam or sex
✅ To-Do This Week
- Confirm your pregnancy with a blood test at your doctor
- Research prenatal care providers and hospitals
- Start a pregnancy journal
- Eat small, frequent meals to help with nausea
- Stay hydrated — aim for 8-10 glasses of water daily
- Get plenty of rest
🩺 Questions for Your Doctor
- ?Is it normal not to have many symptoms yet?
- ?What can I do about morning sickness?
- ?When will we be able to hear the heartbeat?
- ?Should I be concerned about cramping?
- ?What genetic testing options are available?
- ?How much weight should I expect to gain?
📚 References
- [1]ACOG Practice Bulletin No. 189: Nausea and Vomiting of Pregnancy. Obstet Gynecol. 2018;131(1):e15-e30.
- [2]ACOG Practice Bulletin No. 200: Early Pregnancy Loss. Obstet Gynecol. 2018;132(5):e197-e207.
- [3]ACOG Practice Bulletin No. 193: Tubal Ectopic Pregnancy. Obstet Gynecol. 2018;131(3):e91-e103.
Editorial review: Samantha L. Fox, RN, BSN, MSN. Last reviewed: see footer.
Your baby is the size of a...