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Diagnosis of Spina Bifida and Other Dysraphisms in the Fetus

Introduction Anomalies of the fetal spine, particularly spina bifida, are amongst the commonest fetal malformations detectable. Anencephaly and spina bifida are the commonest neural tube defects (NTDs), accounting for up to 95% of all NTDs, and they occur with a nearly equal frequency of 1 in 1000 births though there is some variation depending on geographic location and sex of the fetus. Historically the UK and…

Cranial Abnormalities

Embryology Introduction The rate of change in the appearances of the developing fetal brain is quite remarkable and ultrasound has undoubtledly opened a new window into developing embryology. However it is important to realize that normality of the brain can only be determined if the gestational age is accurately known, and with knowledge and appreciation of the evolution and development of the human brain. It is…

Fetal Growth

Introduction Fetal size and weight at birth are functions of genetic potential and substrate supply. Genetic factors are largely responsible for growth control in the first half of pregnancy, whereas environmental factors are more important in the second half of pregnancy. Normal fetal growth relies on three things; normal implantation, trophoblastic invasion of maternal spiral arterioles and development of chorionic villi. Fetal growth is important because…

Assessment of Twin Gestation

Introduction About 1 in 89 spontaneous conceptions results in the birth of twins. However, with the widespread use of artificial reproductive technologies, the incidence of twinning has increased dramatically worldwide, so that in some countries twins now occur once in every 30 pregnancies. Of spontaneously conceived twins, 55% are dizygotic, whereas 45% are monozygotic. Monozygotic cleavage therefore occurs in about 1 of 200 spontaneous conceptions. Dizygotic…

Diagnosis of Hydrops and Multiple Malformation Syndromes

Introduction Multiple malformation syndromes may be identifiable by ultrasound following the identification of one abnormality and associated investigations. There are thousands of malformation syndromes, many too rare for the scope of this book and many not amenable to ultrasound identification. However, identification of any malformation should immediately alert the sonographer to look for further abnormalities. This chapter will be a guide for possible syndrome diagnosis following…

Fetal Anomalies – The Geneticist’s Approach

Introduction The geneticist's approach to the unexpected finding of fetal structural malformations is to determine whether they constitute a recognizable abnormal pattern of morphogenesis. The pattern and nature of the anomalies can often suggest the timing and cause of an embryological insult and, together with information gleaned from family and parental medical histories, may be helpful in determining whether the insult was environmental or genetic. The…

Prenatal Diagnosis of Fetal Infections

Introduction Viral infections are a concern to practitioners in prenatal diagnosis, particularly in the interpretation of an abnormal fetal ultrasound examination. It must be emphasized that the risks of transplacental transmission and fetal damage are pathogen- and gestation-specific. An optimal approach requires understanding of: the expected teratogenicity of infection; its potential appearance on ultrasound; the dynamics of the progress of maternal–fetal infection; the anticipated progression of…

Disorders of the Placenta: Localization and Placental Attachment Disorders

Background Placenta praevia and placenta accreta are a source of maternal and fetal morbidity and mortality. They are associated with increasing healthcare costs. Their incidence is rising as the number of Caesarean sections and maternal age increase. The importance of these conditions is reflected by the provision of management guidelines by the Royal College of Obstetricians and Gynaecologists. Development and Structure The human placenta has a…

Amniotic Fluid

Introduction Amniotic fluid (AF) is an essential complex and dynamic environment that changes in nature and amount as pregnancy progresses. Amniotic fluid surrounds the fetus during intrauterine development and normal levels are essential to fetal well-being. The presence of normal amniotic fluid throughout gestation not only allows for normal development of the fetal respiratory and musculoskeletal systems, development and maturation of the gastrointestinal and urinary tracts…

Routine Fetal Anomaly Scan

Introduction Since the introduction of ultrasound scanning into obstetric practice in UK in the 1980s, there has been a considerable change to the role of this test in antenatal care, which has been driven largely by developments in technology. In most units, it is now part of routine screening in pregnancy and its main purpose is considered to be the detection of fetal structural anomalies. However,…

Fetal Aneuploidies

Introduction * Acknowledgement: This study was supported by a grant from the Fetal Medicine Foundation (Charity No: 1037116). Aneuploidies are major causes of perinatal death and childhood disability. Consequently, the detection of chromosomal disorders constitutes the most frequent indication for invasive prenatal diagnosis. However, invasive testing, by amniocentesis or chorionic villus sampling (CVS), is associated with a risk of miscarriage and therefore these tests are carried…

First-Trimester Detection of Fetal Anomalies

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…

Fetal Skeleton

Objectives On completion of this chapter , you should be able to: Describe in detail the embryology of the fetal skeleton Describe the variety of musculoskeletal anomalies that can occur in the fetus Differentiate sonographically among the most common skeletal dysplasias List limb abnormalities and the anomalies that are associated with and unique to specific defects Key Terms Achondrogenesis Achondroplasia Craniosynostosis Heterozygous achondroplasia Homozygous achondroplasia Hypophosphatasia…

Fetal Urogenital System

Objectives On completion of this chapter, you should be able to : Discuss the development of the urogenital and genital system Describe the sonographic appearance of the fetal kidneys and bladder Detail the complications of renal agenesis Describe the sonographic findings associated with abnormalities of the kidney Differentiate renal cystic disease Distinguish between different types of urinary obstruction Identify congenital malformations of the genital system Key…

The Fetal Abdomen

Objectives On completion of this chapter, you should be able to: Describe the development of the digestive system and list the unique features of the fetal abdomen Describe normal development of the stomach and the importance of its sonographic visualization Define abnormalities of the fetal gastrointestinal tract and hepatobiliary system and describe their sonographic findings Key Terms Anorectal atresia Asplenia Choledochal cyst Cholelithiasis Cystic fibrosis Duodenal…

The Fetal Anterior Abdominal Wall

Objectives On completion of this chapter, you should be able to: Describe the embryology of the abdominal wall Define and describe the anterior abdominal wall abnormalities discussed in this chapter List the sonographic findings for an omphalocele and for a gastroschisis Identify the fetal anomalies in pentalogy of Cantrell Explain the sonographic findings in a fetus with amniotic band syndrome Key Terms Amniotic band syndrome Beckwith-Wiedemann…

The Fetal Thorax

Objectives On completion of this chapter, you should be able to: Describe the development of the thoracic cavity List the normal sonographic features of the thorax and diaphragm Describe the development and consequences of pulmonary hypoplasia Differentiate between solid and cystic lesions of the lung Discuss the sonographic findings in a diaphragmatic hernia Key Terms Asphyxiating thoracic dystrophy Bronchogenic cyst Congenital bronchial atresia Congenital cystic adenomatoid…

Fetal Neural Axis

Objectives On completion of this chapter, you should be able to : Describe the embryology of the neural tube fetal brain development Discuss the anomalies that can occur in the fetal head and spine Recognize the sonographic appearance of fetal head and spine anomalies Key Terms Acrania Alobar holoprosencephaly Anencephaly Anomaly Cebocephaly Cyclopia Cystic hygroma Holoprosencephaly Hydranencephaly Hydrocephalus Macrocephaly Meningocele Meningomyelocele Myeloschisis Spina bifida Spina bifida…

Fetal Face and Neck

Objectives On completion of this chapter, you should be able to: Discuss basic embryology of the face Describe how to sonographically evaluate the fetal face and neck for normal features Define the most common face and neck congenital anomalies discovered sonographically in utero Key Terms Agnathia Anotia Anophthalmia Arhinia Beckwith-Wiedemann syndrome Branchial cleft cyst Cebocephaly Cephalocele Craniosynostosis Cyclopia Cystic hygroma (CH) Dacryocystocele Epignathus Encephalocele Ethmocephaly Exophthalmia…