Twining's Textbook of Fetal Abnormalities E-Book

Anne Marie Coady, Sarah Bower

• Publisher: Churchill Livingstone
• Year: 2014
• ISBN:
  9780702054075
• Edition: 3
• Topic: Medicine
• Subtopic: Radiology, Radiotherapy & Nuclear Medicine

Access practical guidance on the radiologic detection, interpretation, and diagnosis of fetal anomalies with Twining's Textbook of Fetal Abnormalities. With fetal scanning being increasingly done by obstetricians, this updated medical reference book features a brand-new editorial team of radiologist Anne Marie Coady and fetal medicine specialist Sarah Bower; these authorities, together with contributions from many other experts, provide practical, step-by-step guidance on everything from detection and interpretation to successful management approaches. Twining's Textbook of Fetal Abnormalities is a resource you'll turn to time and again!

• Consult this title on your favorite e-reader, conduct rapid searches, and adjust font sizes for optimal readability.
• Quickly access specific information with a user-friendly format.
• Deliver a rapid, reliable diagnosis thanks to a strong focus on image interpretation, as well as the correlation of radiographic features with pathologic findings wherever possible.
• Clearly visualize a full range of conditions with help from more than 700 images.

• Stay abreast of the latest developments in detecting fetal abnormalities with 4 brand-new chapters: Fetal Growth; Haematological Disorders; Fetal Pathology; and Fetal Tumours.
• Access increased coverage of fetal growth, first trimester anomalies, DDX, and clinical management.
• Understand the major advances in today's hottest imaging technologies, including 3-D Ultrasound, Fetal MRI, and Colour Doppler.
• Effectively interpret the images you encounter with highly organized coordination between figures, tables, and imaging specimens.

Chapter 1

First-Trimester Detection of Fetal Anomalies

Raffaele Napolitano, Aris T Papageorghiou

Chapter Outline

Introduction

Viability, Multiple Pregnancy and Gestational Age Assessment

Diagnosis of Fetal Abnormalities

Considerations of Embryological Development

First-Trimester Screening for Fetal Abnormalities

Nuchal Translucency Screening for Fetal Abnormalities

Normal Appearances (Sonoembryology)

Gestational Sac, Yolk Sac and Fetal Pole

Central Nervous System

The Heart

Urinary Tract

The Abdomen

Extremities

The Face

Fetal Abnormalities

Central Nervous System Anomalies

Urinary Tract Abnormalities

Abnormalities of the Gastrointestinal Tract

Thoracic Abnormalities

Skeletal Abnormalities

Abnormalities of the Hands and Feet

Abnormalities of the Face and Neck

References

Introduction

The first trimester of pregnancy is generally considered to be the first 13 completed weeks. In the past, first-trimester ultrasound has mainly been used to confirm fetal viability, establish pregnancy location, count the number of fetuses and assess gestational age by measurement of fetal crown rump length (CRL). A major breakthrough in screening for fetal abnormalities was the finding that fetal nuchal translucency is increased in cases of chromosomal abnormalities and other fetal anatomical defects, and this forms the basis of screening for chromosomal abnormalities in many countries. With further improvements in ultrasound technology it has become increasingly feasible to examine the fetal anatomy in the first trimester. It is advisable to perform the scan at 11 + 0 to 13 + 6 weeks' gestation as this allows confirmation of viability, accurate assesment of gestational age and number of viable fetuses in addition to evaluation of anatomy and calculation of risk of aneuploidy.¹ There are a number of differences and advantages to screening for abnormalities in the first trimester over the second trimester (Table 1-1). The recently published guidelines on the first trimester scan by the International Society of Obstetrics and Gynaecology lists the structures which it should be possible to visualize and assess in the first-trimester routine screening examination.² (Table 1-2).

TABLE 1-1

Advantages and Disadvantages to Screening for Abnormalities in the First Trimester Over the Second Trimester

Advantages of First-Trimester Scanning	Disadvantages of First-Trimester Diagnosis of Fetal Anomalies
Establishing fetal viability and excluding early pregnancy complications	Difficulties in technique of transvaginal fetal scanning
Confirming multiple pregnancy and determining chorionicity	Inability to detect all abnormalities due to the natural history of some anomalies
Accurate dating for estimated date of delivery and as a baseline for both first- and second-trimester biochemical screening	Significance of minor anomalies unclear at present
Early detection of fetal abnormalities	Pitfalls in first-trimester diagnosis of fetal anomalies
Termination of pregnancy may be carried out as a suction curettage	No pathological confirmation of diagnosis
Nuchal translucency measurement for the detection of chromosomal disease, and as a marker for other syndromes and structural abnormalities, especially cardiac anomalies	High spontaneous loss rate in fetuses with major abnormalities

TABLE 1-2

Suggested Anatomical Assessment at Time of 11 to 13+6-week scan

Organ/Anatomical Area	Present and/or Normal?
Head	Present
	Cranial bones
	Midline falx
	Choroid-plexus-filled ventricles
Neck	Normal appearance
	Nuchal translucency thickness (if accepted after informed consent and trained/certified operator available)
Face	Eyes with lens*
	Nasal bone*
	Normal profile/mandible*
	Intact lips*
Spine	Vertebrae (longitudinal and axial)*
	Intact overlying skin*
Chest	Symmetrical lung fields
	No effusions or masses
Heart	Cardiac regular activity
	Four symmetrical chambers*
Abdomen	Stomach present in left upper quadrant
	Bladder*
	Kidneys*
Abdominal wall	Normal cord insertion
	No umbilical defects
Extremities	Four limbs each with three segments
	Hands and feet with normal orientation*
Placenta	Size and texture
Cord	Three-vessel cord*

^* Optional structures.

Viability, Multiple Pregnancy and Gestational Age Assessment

About 2.8% of pregnancies will be non-viable at 10–13 weeks of gestation and chromosomal abnormalities may be present in 45–70% of these.³ First-trimester ultrasound is highly accurate in diagnosis of non-viable pregnancies, but it is important to ensure that missed miscarriage is distinguished from a very early viable pregnancy where the fetal heartbeat is simply not seen. This should be of particular concern within the first 6–8 weeks. Recent studies suggest that a mean sac diameter (MSD) cut-off of over 25 mm and a CRL of over 7 mm minimizes the risk of a false-positive diagnosis of miscarriage⁴ (Figures 1-1 and 1-2). In cases where these measurements are below the threshold for a one-stop diagnosis a further scan should be arranged in 7 days to assess embryonic or sac growth in that interval.

FIGURE 1-1 A large gestation sac MSD >25 mm lacking an embryo which is consistent with early pregnancy failure. (Courtesy of Dr Anne Marie Coady.)

FIGURE 1-2 An embryo of CRL over 7 m...