4 weeks pregnant: Key points

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Changes for mum

  • Your baby is starting its second week of growth and you may notice some early symptoms of pregnancy.
  • Your heart rate may increase slightly because your blood volume increases so that there is enough blood to support your baby.
  • You may feel tired because of all the extra work your body is doing to pump the extra blood through your system.
  • Your breasts may feel sore or tender and become darker around the nipples.
  • You may feel emotional as a result of all the hormonal changes of pregnancy, or because of anticipation or concerns related to pregnancy. Mood swings are normal so don’t worry if you experience them.
  • Your doctor may notice changes in the colour of your cervix.
  • The placenta which nourishes your baby during pregnancy has started producing hCG (human chorionic gonadotropin) the pregnancy hormone which pregnancy tests detect.

Changes for baby

  • Your baby, still known as a blastocyst, finishes the process of implanting into the lining of your womb this week.
  • Blood vessels which attach your baby and the placenta begin growing.
  • Your baby is still less than a millimetre in length- that’s about the thickness of eight sheets of paper.
  • The cells which make up the blastocyst separate into three layers from which all the different cells of your baby, for each of the different structures of your baby’s body (e.g. the nervous system, the eyes) are produced.
  • The amniotic sac with fluid which surrounds and protects your baby during pregnancy forms this week.

Doctor appointments and tests

  • If you have not yet visited your doctor for preconception care you should do so this week, to ensure you are healthy and ready to grow a healthy baby.
  • Although your body is producing pregnancy hormone hCG, it’s too early for a reliable pregnancy test result. Wait until you’re 5 weeks pregnant.
  • A pregnancy test this week won’t do any harm, but if the test is negative, check again next week as it’s possible you’re pregnant but your hCG levels are still too low to detect.

Health and lifestyle information

  • Ensure you’re eating a nutritious diet with plenty of fruit and vegetables and avoiding foods which may be harmful in pregnancy.
  • If you haven’t already, start exercising! It’s not only safe, staying active in pregnancy is good for you and your baby and if you start now, you’re more likely to keep it up throughout pregnancy.
  • Keep having sex if you’re in the mood. Unless your doctor has advised you shouldn’t as you’re a ‘high risk’ pregnancy, both intercourse and orgasm are safe and won’t do any harm to your baby.

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More information on the 4th week of pregnancy

For more information on the fourth week of pregnancy, see 4 weeks pregnant.
For more information on the pregnancy symptoms which occur before a woman even knows she’s pregnant, see Changes for mum this week.
For more information on the changes happening to growing babies in the fourth week of pregnancy, see Changes for baby this week.
For more information on doctor appointments and other lifestyle changes to adopt, see Pregnancy health and lifestyle information this week.
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Date Created: August 23, 2012 Date Modified: August 29, 2012