Читать книгу Infants and Children in Context - Tara L. Kuther - Страница 118

In your view, what are the most important challenges internationally adopted children and their families face? Identify sources and forms of support that might help adopted children and their parents.

The most widespread and routine diagnostic procedure is ultrasound, in which high-frequency sound waves directed at the mother’s abdomen provide clear images of the womb represented on a video monitor. Ultrasound enables physicians to observe the fetus, measure fetal growth, judge gestational age, reveal the sex of the fetus, detect multiple pregnancies (twins, triplets, etc.), and determine physical abnormalities in the fetus. Many deformities can be observed, such as cardiac abnormalities, cleft palate, and microencephaly (small head size). At least 80% of women in the United States receive at least one prenatal ultrasound scan (Sadler, 2018). Three to four screenings over the duration of pregnancy are common to evaluate fetal development (Papp & Fekete, 2003). Repeated ultrasound of the fetus does not appear to affect growth and development (Stephenson, 2005).

Ultrasound technology enables health care professionals to observe the fetus, measure fetal growth, detect physical abnormalities, and more.

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Fetal MRI applies MRI technology to image the fetus’s body and diagnose malformations (Griffiths et al., 2017). Most women will not have a fetal MRI. It is often used as a follow-up to ultrasound imaging to provide more detailed views of any suspected abnormalities (Milani et al., 2015). Fetal MRI can detect abnormalities throughout the body, including the central nervous system (Saleem, 2014). MRI in the obstetrical patient is safe for mother and fetus in the second and third trimesters but is expensive and has limited availability in some areas (Patenaude et al., 2014).

Amniocentesis is a prenatal diagnostic procedure in which a small sample of the amniotic fluid that surrounds the fetus is extracted from the mother’s uterus through a long, hollow needle that is guided by ultrasound as it is inserted into the mother’s abdomen (Odibo, 2015). The amniotic fluid contains fetal cells, which are grown in a laboratory dish to create enough cells for genetic analysis. Genetic analysis is then performed to detect genetic and chromosomal anomalies and defects. Amniocentesis is less common than ultrasound, as it poses greater risk to the fetus. It is recommended for women aged 35 and older, especially if the woman and partner are both known carriers of genetic diseases (Vink & Quinn, 2018a). Usually amniocentesis is conducted between the 15th and 18th weeks of pregnancy. Conducted any earlier, an amniocentesis may increase the risk of miscarriage (Akolekar et al., 2015). Test results generally are available about 2 weeks after the procedure because it takes that long for the genetic material to grow and reproduce to the point where it can be analyzed.

During amniocentesis, ultrasound is used to guide the insertion of a long, hollow needle into the mother’s abdomen in order to extract a sample of the amniotic fluid that surrounds the fetus. The amniotic fluid contains fetal cells, which are grown in a laboratory dish and tested for genetic and chromosomal anomalies and defects.

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Chorionic villus sampling (CVS) also samples genetic material and can be conducted earlier than amniocentesis, between 10 and 12 weeks of pregnancy (Vink & Quinn, 2018b). CVS requires studying a small amount of tissue from the chorion, part of the membrane surrounding the fetus. The tissue sample is obtained through a long needle inserted either abdominally or vaginally, depending on the location of the fetus. Results are typically available about 1 week following the procedure. CVS is relatively painless and, like amniocentesis, has a 100% diagnostic success rate. Generally, CVS poses few risks to the fetus (Beta, Lesmes-Heredia, Bedetti, & Akolekar, 2018; Shim et al., 2014). However, CVS should not be conducted prior to 10 weeks’ gestation, as some studies suggest an increased risk of limb defects and miscarriages (Shahbazian et al., 2012).

Noninvasive prenatal testing (NIPT) screens the mother’s blood to detect chromosomal abnormalities. Cell-free fetal DNA (chromosome fragments that result in the breakdown of fetal cells) circulates in maternal blood in small concentrations that can be detected and studied by sampling the mother’s blood (Warsof, Larion, & Abuhamad, 2015). Testing can be done after 10 weeks, typically between 10 and 22 weeks. Given that the test involves drawing blood from the mother, there is no risk to the fetus. The use of NIPT has increased dramatically in the United States and other countries (Hui, Angelotta, & Fisher, 2017). However, NIPT cannot detect as many chromosomal abnormalities as amniocentesis or CVS and does so with less accuracy (Chan et al., 2013; National Coalition for Health Professional Education in Genetics, 2012). Researchers have identified the entire genome sequence using NIPT, suggesting that someday, NIPT may be as effective as other, more invasive techniques (Tabor et al., 2012). Pregnant women and their partners, in consultation with their obstetrician, should carefully weigh the risks and benefits of any procedure designed to monitor prenatal development.