Morning sickness
Why nausea and vomiting happen in pregnancy, when they ease, what helps and when to call a doctor.
3 min read
First trimester
Week 5 of pregnancy
Your baby is the size of a sesame seed. The neural tube, which becomes the brain and spine, is forming, and the tiny heart starts to beat.
Your baby is the size of a sesame seed
- Length, head to bottom
- ≈ 2 mm
Your baby this week
- The neural tube forms; the brain, spinal cord and nerves will develop from it.
- The heart, still a simple tube, starts to beat towards the end of this week.
- The embryo is shaped like a tiny spoon and is about 2 millimetres long.
Your body this week
- Nausea, usually called morning sickness even though it comes at any time of day, may start this week.
- You may need to wee more often, because your blood volume rises and your kidneys work harder.
- Your breasts may feel swollen and tender, and your mood can change quickly.
- Some women notice a metallic taste or go off certain foods and smells.
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General information written by the mam.al editors. Every pregnancy is different and sizes are averages; it does not replace advice from your doctor or midwife. Sources include the NHS week-by-week guide to pregnancy. NHS. Contains public sector information licensed under the Open Government Licence v3.0.