First trimester · 5 weeks pregnant
Week 5: the heart begins
The neural tube forms and the tiny heart starts to beat.
The embryo now looks like a tiny tadpole. The groove that becomes the brain and spinal cord is closing, and a simple heart tube starts to contract by the end of the week.
Size and weight
About the size of
a sesame seed
Length
1.5–2.5 mm
Weight
—
Averages from standard growth charts. Measured crown to rump until week 20 and head to heel afterwards.
How your baby is developing
- The neural tube forms along the back; it will become the brain and spinal cord.
- A primitive heart and circulation form; the heart begins to beat around day 22 after conception.
- Early buds for the arms appear, and the placenta begins to form in earnest.
How you may feel
- Nausea, with or without vomiting, which can start now
- Needing to pass urine more often
- Exhaustion
- Food aversions and a sharpened sense of smell
- Mood swings
Nausea is caused by rising hormones and usually peaks around 9 to 10 weeks. Eating small amounts often helps more than large meals.
What's next
Tests and appointments
- A blood test can confirm the pregnancy if there is any doubt.
- Register at your polyclinic's prenatal office if you have not done so; aim for the first visit by 10 weeks.
What to do this week
- Eat small, frequent snacks: plain crackers by the bed, ginger tea, cold foods if smells bother you.
- Drink plenty of water, in sips if large amounts make you nauseous.
- Rest when you can; early fatigue is normal and temporary.
- Ask a doctor before taking any medicine, including herbal remedies.
Call your doctor or maternity hospital if
- Bleeding that is heavier than light spotting, or bleeding with cramps
- Severe pain on one side of your lower abdomen, or pain with dizziness or fainting
- Vomiting so often that you cannot keep fluids down for 24 hours
- A temperature of 38 °C or higher, or pain when you pass urine
If something feels wrong, trust yourself and call 103 or your maternity hospital. You will never be wasting anyone's time.
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