First trimester
Week 4 It begins, quietly
About the size of a poppy seed1 mmunder 1 g
Your baby
Your baby is a tiny ball of cells settling into the lining of your womb, and the placenta is starting to form.
You
Your period is late. Some people notice sore breasts, tiredness or light spotting.
This week
Take a home test, and start folic acid (400 micrograms a day) if you have not already.




