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FAQ: Prenatal Screening for Birth Defects and Common Genetic Conditions
Prenatal testing is a way to measure a pregnancy's risk for several common genetic conditions, 包括唐氏综合症. 是否进行这些测试取决于个人. The conditions that can be detected are typically caused by genetic changes that occur during a pregnancy rather than conditions inherited from either biological parent. Prenatal testing can also assess the risk of certain birth defects.
The screening options described on this page are considered noninvasive. They are performed using either a blood test or an ultrasound exam.
- Down syndrome. 也叫21三体, Down syndrome happens when a fetus has an extra copy (full or partial) of chromosome 21. Babies born with this condition have a higher chance of certain birth defects, 比如心脏或肠道异常. People with Down syndrome have a distinct physical appearance and mild to moderate intellectual disability. 大多数都能活到成年. 了解更多关于 唐氏综合症的产前检测选择.
- 18三体和13三体. These chromosomal disorders cause severe intellectual disability and medical issues in many parts of the body. Most babies born with one of these conditions don't survive past the first year.
- 神经管缺损. These neurological birth defects affect the brain or spinal cord. The most common neural tube defects are spina bifida (a spinal malformation) and anencephaly (parts of the brain or skull are missing).
- Some prenatal screening tests can assess the risk of certain other birth defects, 包括腹壁发育的问题.
加州所有孕妇都可以使用 加州产前筛查(CA PNS). The process for this noninvasive screening, known as sequential integrated screening, has two parts:
- 无细胞DNA筛选. 这个血液测试, 至少在怀孕10周后进行, 如何评估患唐氏综合症的风险, 18三体和13三体. 该测试还可以预测胎儿的性别.
- 母体血清甲胎蛋白(MSAFP)筛查. 这个血液测试, 在怀孕15到21周之间进行, 能否评估神经管缺损的风险, 以及腹壁的缺陷.
UCSF also offers and recommends an additional screening option:
- 颈部半透明(NT)筛查. 这种超声波, 在怀孕11到14周之间进行, 测量胎儿颈部后方的空间, which can indicate possible chromosomal changes or birth defects.
大多数孕妇都有资格. However, those who fit any of the following categories are ineligible, 由于测试精度降低:
- 怀两个以上胎儿的
- Vanishing twin syndrome (the loss of one twin) affecting the current pregnancy
- Individuals who have had an organ transplant or currently have active cancer
- Positive. 胎儿患某种特定疾病的风险会增加.
- Negative. 胎儿患病的风险并不会增加.
- Indeterminate. The test didn't reveal enough information to show whether the fetus has an increased risk for the condition. 如果发生这种情况,您的提供者可以重新执行测试.
产前检查有助于评估风险,但不是诊断. A positive or negative result doesn't definitively indicate whether a pregnancy has a specific condition.
Prenatal screening is optional, and your provider will support your decision either way. Some patients opt for prenatal screening because learning about possible risks for genetic conditions would help them prepare or make decisions about the pregnancy.
No test can detect all possible health and developmental concerns in a pregnancy.
产前筛查测试不是100%准确的. 会出现假阳性和假阴性. These tests are also not diagnostic: They show the risk of a specific condition, 而不是胎儿是否受到某种特殊情况的影响.
其他基因测试,包括 绒毛取样 and amniocentesis, may provide more definitive information about genetic risks in a pregnancy. Talk to a genetic counselor to learn more about your options.
The tests described on this page are blood tests or ultrasound exams that don't pose any physical risk for the pregnancy.
Though it happens rarely, a prenatal genetic test could reveal information about your own health. For example, you might find out that you have a chromosome abnormality.
如果检查显示你怀孕的风险增加, you will be referred to a genetic counselor to discuss your options. 你的遗传咨询师可能会建议你做进一步的检测.
If you have questions about prenatal genetic screening and testing, or you'd like to schedule an appointment with a genetic counselor, 请与 UCSF产前诊断中心.
UCSF Health medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your provider.