Diagnostic ultrasound ( PDFDrive )

1224 PART IV Obstetric and Fetal Sonography
A
S
D
A
L5
B
FIG. 35.10 Posterior Longitudinal Scan Plane. (A) Diagram shows
the incident sound beam (arrows) relecting off the posterior surface
of the centrum. If there is no ossiication in the laminae near the midline,
the laminae will not be visible on the scan; only the centra will be seen.
If the laminar ossiication is present near the midline, the centra and
laminae will be seen as echogenic foci. The red structures are ossiied
portions of the vertebra. (B) Posterior longitudinal scan of the lumbosacral
spine at 15 weeks shows ossiication in the centra of the lower thoracic,
lumbar, and sacral spine (L5, centrum of vertebra). In this midline scan,
no ossiication is present posterior to the posterior surface of the dural
sac (D). S, Skin surface.
Folic Acid Fortiication
Another major factor in the decline of the incidence of NTDs
is the use of folic acid to prevent NTDs. Several clinical trials
have demonstrated a decreased risk of NTDs by at least 60%
with the maternal use of periconceptual folic acid supplements. 39-43
he reduction occurs in mothers with previously afected pregnancies
and in mothers without this risk. In 1992 the U.S. Department
of Health and Human Services 44 and the Expert Advisory Group
in the United Kingdom 45 recommended supplementation of
0.4 mg of folic acid for women in the general population trying
to conceive. Women who are at high risk because of a previously
afected fetus should take 4 mg of folic acid daily. 1 Routine folic
acid supplementation around the time of conception confers a
72% to 87% decrease in probability of NTDs. 3,40 However, this
B
FIG. 35.11 Posterior Angled Transaxial (Transverse) Scan
Plane. (A) Diagram shows the incident sound beam (arrows) relecting
off the posterior aspects of the laminae and portions of the pedicles.
The beam may also relect off the ossiied centrum. This scan plane
can depict the entire ring of ossiication of the spinal canal. The red
structures are ossiied portions of the vertebra. (B) Endovaginal scan
at 18 weeks in the midlumbar spine outlines the curvilinear structure
of each neural arch (short arrows, lamina plus pedicle) and the ossiied
centrum (long arrow). Together these structures form the ossiied ring
of the spinal canal.
knowledge and these recommendations have not translated into
a reduction of the incidence of NTDs in the general population, 46,47
largely because only a minority take folic acid routinely in the
reproductive years, and in those who do, supplementation may
not be taken at the proper time. Studies in the 1990s demonstrated
that less than 45% of pregnant women took folic acid before
conception. 48-50 In 2007, 40% of all U.S. women of reproductive
age (15-45 years) took daily supplements of folic acid. Daily
supplements could be one serving of breakfast cereal fortiied
with 100% of the recommended daily value of folic acid or a
supplement with 0.4 mg of folic acid daily. 4
Another strategy to increase folic acid levels is the systematic
fortiication of food stufs with folic acid. In March 1996 the