Prior fetus or neonate with a structural or genetic/chromosomal abnormality
Current pregnancy with known or suspected fetal abnormality or confirmed growth abnormality
Maternal diabetes diagnosed before 24 weeks' gestation Assisted repr0ductive technology to achieve conception Matenal prepregnancy body mass index >30 kg/m2 Multifetal gestation (Chap. 45, p. 864)
Nuchal translucency measurement ::3.0 mm
Parental carriage of genetic/chromosomal abnormality
Maternal age ::35 at delivery
Nuchal translucency measurement ::3.0 mm
Other condition affecting the fetus
Congenital infection (Chaps. 64 and 65)
Alloimmunization (Chap. 15, p. 301)
Amnionic fluid abnormality (Chap. 11l, p. 227)
Modified from Jax, 2014, 2015.
gestational age. Oligohydramnios indicates an amnionic fluid volume below normal range, and subjective crowding of the fetus is often noted. Hydramnios-also calledpoyhydramniosdefines a volume above a given normal threshold. Amnionic luid volume is usually assessed semiquantitatively. Measurements include either the single deepest vertical luid pocket or the sum of the deepest vertical pockets from each of four equal uterine quadrants-the amnionic luid index (Phelan, 1987). Reference ranges have been established for both measurements from 16 weeks' gestation onward. he single deepest vertical pocket is normally between 2 and 8 cm, and the amnionic luid index normally ranges between 8 and 24 cm. A further discussion and images are provided in Chapter 11 (p. 227).
Evaluation of the relationship between the placenta and the internal cervical os is an essential component of the standard sonogram. Abnormalities of the placenta and umbilical cord are reviewed in Chapter 6 (p. 111). Although the cervix may be imaged transabdominally (Fig. 10-4), this is often limited
FIGURE 10-4 A. Transabdominal image of the cervix depicting the internal os and external as. B. Transvaginal imaging a more accurate evaluation of the cervix and should be used for medical decision-making. In this image, arrowheads mark the endocervical canal. (Used with permission from Dr. Emily Adhikari.)
TABLE 10-8. Criteria for Transvaginal Evaluation of the Cervix
Imaging the Cervix
Maternal bladder should be empty.
Transducer is inserted under real-time observation, identiying midsagittal intenal os, and then extenal os, while keeping the internal os in view.
Internal os, external os, and entire endocervical canal should be visible. The internal os may appear as a small triangular indentation at the junction of the amnionic cavity and endocervical canal.
Image is enlarged so that the cervix fills approximately 75% of the screen.
Anterior and posterior width of the cervix should be approximately equal.
Transducer is pulled back slightly until the image begins to blur, ensuring that pressure is not placed on the cervix, then inserted only enough to restore a clear image.
and without fundal or suprapubic pressure, to assess for dynamic change-or shortening on real-time imaging.
Measuring the Cervix
Calipers are placed where anterior and posterior walls of cervix meet.
Endocervical canal appears as a faint, linear echodensity.
If canal has a curved contour, a straight line between the internal and external os will deviate from the path of the endocervical canal.
If midpoint of the line between the internal and external canal deviates by �3 mm from the endocervical canal, measure the cervical length in two linear segments.
Funneling, sludge (debris), or dynamic change is noted.
At least three separate images are measured during a period of at least 3 minutes to allow for dynamic change.