This detailed ultrasound scan, sometimes called the mid-pregnancy or anomaly scan, is usually carried out when you're between 18 and 21 weeks pregnant.
The 20-week screening scan is offered to everybody, but you do not have to have it if you do not want to.
The scan checks the physical development of your baby, although it cannot pick up every condition.
The 20-week screening scan is carried out in the same way as the12周扫描. It produces a 2D black and white image that gives a side view of the baby. The NHS screening programme does not use 3D or colour images.
The scan is a medical examination. You'll be asked to give your permission for it to be carried out.
Make sure you understand what's going to happen, and feel free to ask any questions.
扫描要寻找什么？
为期20周的筛查扫描详细介绍了婴儿的骨头，心脏，大脑，脊髓，脸部，肾脏和腹部。
它允许超声检查员寻找11种罕见情况。扫描只能寻找这些条件，找不到所有可能是错误的条件。
您可以在gov.uk的这些传单中找到有关每种情况（包括治疗选择）的更多信息：
- anencephaly
- open spina bifida
- cleft lip
- diaphragmatic hernia
- 胃肠道
- exomphalos
- serious cardiac abnormalities
- bilateral renal agenesis
- lethal skeletal dysplasia
- Edwards' syndrome, or T18
- Patau's syndrome, or T13
在大多数情况下，扫描将表明婴儿似乎正在按预期发展，但有时超声检查员会发现或怀疑一些不同的东西。
如果有条件，扫描会找到吗？
某些条件比其他条件更清晰。例如，有些婴儿有一个称为开放的疾病spina bifida，影响脊髓。
This can usually be seen clearly on a scan, and will be detected in around 9 out of 10 babies who have spina bifida.
其他一些情况，例如心脏缺陷，更难看到。扫描将发现有心脏缺陷的婴儿中约有一半（10个）。
Some of the conditions that can be seen on the scan, such ascleft lip，将意味着婴儿出生后可能需要治疗或手术。
在少数情况下，发现了一些非常严重的疾病，例如，婴儿的大脑，肾脏，内部器官或骨骼可能无法正常发展。
In some very serious, rare cases where no treatment is possible, the baby will die soon after they're born or may die during pregnancy.
在20周的扫描中会发生什么？
大多数扫描是由特殊培训的员工进行的，称为超声师。扫描是在昏暗的房间中进行的，因此超声检查员可以获得婴儿的良好图像。
您会被要求躺在沙发上，将裙子或裤子放到臀部，然后将顶部抬到胸部，以便发现腹部。
The sonographer or their assistant will tuck tissue paper around your clothing to protect it from the gel, which will be put on your tummy.
然后，超声检查员将手持式探针通过您的皮肤检查婴儿的身体。凝胶确保探针和皮肤之间有良好的接触。婴儿的黑白图像将出现在超声屏幕上。
Having the scan does not hurt, but the sonographer may need to apply slight pressure to get the best views of the baby. This might be uncomfortable.
The sonographer needs to keep the screen in a position that gives them a good view of the baby. The screen may be directly facing them, or at an angle.
Sometimes the sonographer doing the scan will need to be quiet while they concentrate on checking your baby. But they'll be able to talk to you about the pictures once they've completed the check.
The appointment for the 20-week screening scan usually takes around 30 minutes.
有时，如果婴儿躺在尴尬的位置或四处移动，或者您的体重高或身体薄纸密集，则很难获得好照片。这并不意味着有什么可担心的。
You may need to have a full bladder when you come for the appointment. The doctor or midwife looking after you will let you know before you come. If you're not sure, you can contact them and ask.
我可以找出婴儿的性别吗？
If you want to know your baby's sex, you should ask the sonographer at the start of the scan, so they know that they need to check.
一些医院可能拒绝告诉您婴儿的性爱。与您的超声医生或助产士交谈以了解更多信息。
Can my partner or a friend come to the scan with me?
Yes. The 20-week screening scan can sometimes find the baby has a health condition. You may like someone to come with you to the scan appointment.
Most hospitals do not allow children to attend scans as childcare is not usually available. Ask your hospital about this before your appointment.
扫描会伤害我还是我的孩子？
There are no known risks to the baby or you from having an ultrasound scan, but it's important to think carefully about whether to have the scan or not.
它可能会提供可能意味着您必须做出一些重要决定的信息。例如，您可能会为您提供有流产风险的进一步测试，并且您需要决定是否要进行这些测试。
Do I have to have this scan?
No – it's your choice whether to have it or not. Some people want to find out if their baby has a condition, and some do not.
如果您选择不进行扫描，那么您的怀孕护理将保持正常状态。
When will I get the results of the scan?
The sonographer will be able to tell you the results of the scan at the time.
如果扫描显示一些东西怎么办？
Most scans show that the baby seems to be developing as expected.
如果发现或怀疑任何条件，超声检查员可能会要求其他工作人员看扫描并发表第二意见。
扫描找不到所有条件，而且总是有可能出生的婴儿出生，因为扫描看不见的健康问题。
Will I need any further tests?
如果扫描显示可能有些东西，可能会为您提供另一项测试以确定。
If you're offered further tests, you'll be given more information about the tests so you can decide whether or not you want to have them.
您将可以与您的助产士或顾问讨论这一点。如有必要，您可能会在另一家医院转介专家。