Week 21 of pregnancy (Days 147-153)

Your growing baby now measures 27cm from crown to heel and weighs approximately 300g. Around this week you will have your Anomaly Scan

Trimester Chart
A Guide to each week of your pregnancy, with details on your baby’s growth, your body and symptoms to look out for.
  • 4

    Your baby is no longer a zygote or a single cell. The cells have multiplied rapidly and now the embryo is taking shape.

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  • 9

    From week 9 you can have Non-Invasive Prenatal Screening, to assess your risk of Down's Syndrome and other conditions.

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  • 13

    This week marks the end of the first trimester, and the risk of miscarrage reduces dramatically.

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1st Trimester

 

 

 
  • 14

    Your baby now measures around 8cm, from crown to rump and weighs around 40g.

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  • 22

    Your growing baby now measures 28cm from crown to heel and weighs approximately 350g.

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  • 28

    Your growing baby now measures 38cm from crown to heel and weighs approximately 1kg.

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2nd Trimester

 

 

 
  • 29

    Your growing baby now measures 39cm from crown to heel and weighs approximately 1.1kg.

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  • 36

    Your growing baby now measures up to 47.5cm from crown to heel and weighs approximately 2.7kg.

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  • 40

    Your baby is now considered full term and will not normally gain much weight at this point.

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3rd Trimester

 

 

 

 

Baby

At week 21 of pregnancy, the fetus measures approximately 27cm from crown to heel. From this point, the fetus is measured from crown to heel, rather than from crown to rump. Fetal weight is around 300g at this stage. The digestive system is now fully formed and the fetus is able to swallow amniotic fluid.

The amniotic fluid provides some nutrition, hydration and also helps to practice digestion. This also means that the fetus is able to taste some of the foods that you eat.

If the fetus is female, the uterus is fully formed now and the vaginal canal is also starting to develop and form. If the fetus is male, the testicles are now formed and are beginning to descend from the abdomen. They will descend fully when the scrotal sac has completed its development in the coming weeks. Although the reproductive systems are not fully formed, the external genitals may be visible on an ultrasound scan, making it possible to determine the sex of the fetus. Both the eyebrows are eyelids are now fully developed.

You

You may be feeling fetal movement by now and it is likely that the movements are becoming stronger and more purposeful, feeling more like kicks and nudges than fluttering. You may also be starting to notice a pattern of resting and activity in the movements.

Around this time, some women start to experience colostrum leaking from their breasts. This substance looks like milk, and is indeed the first form of milk that your body produces. You may also be starting to notice the appearance of stretch marks on your belly and/or breasts. Stretch marks occur when the tissue under the skin is torn when the skin is stretched. Stretch mark creams are available to buy, although there is no evidence of their benefit in reducing stretch marks.

Many women suffer from hot flushes during mid-pregnancy. This is caused by increased blood flow and is perfectly normal. If you are struggling with hot flushes, it may help to wear loose fitting clothing and avoid synthetic fabrics. Some women also notice changes in skin, hair and fingernails and toenails. Hair and nails may grow more quickly during pregnancy due to increased blood circulation bringing extra nutrients to hair follicles. Inflamed and/or bleeding gums are another common symptom during pregnancy and are, once again, the results of pregnancy hormones leading to an enriched blood supply. Avoiding sticky, sweet foods can help to reduce the amount of bacteria in the mouth and help to reduce inflammation.

If you haven’t already had your second scheduled scan, you may have it this week. The scan will check fetal growth and also look at the development of the spine and internal organs.

At this time in the pregnancy there is often a sense of wellbeing and an absence of symptoms. However there may be troublesome aches and pains in the bones and muscles. These come and go. There should be no bleeding or significant abdominal pain. The fetal movement may be felt later with a first baby than if you have had one before. The sensation starts as initial flutterings and develop gradually into discrete movements.

What is routinely offered on NHS

The NHS offers an anomaly scan between 18 and 22 weeks. A better and more detailed view of the baby will be seen at 20 to 22 weeks. This provides better detail about organs such as the heart. If the baby is not in an ideal position the sonographer may find it difficult to assess the full detail and you may be asked to move around or come back later. If the sonographer has any difficulty or there are abnormal findings then you will be asked to return to see a specialist doctor. After this scan you will have an appointment with the midwife or, if there are any problems, the consultant.

What other care is available

If you want additional advice you can refer yourself to a private clinic. There you can have an appointment with a midwife, specialist and you can have a high quality ultrasound scan. If you do not have confidence in the NHS scan for whatever reason it can be repeated. In a private clinic there should be more time, often better equipment and access to highly skilled expertise. If you have had a previous late miscarriage or carry twins then a cervical scan is readily available.

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