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Evidence for Routine Ultrasound Screening for Fetal Abnormalities in the Second and Third Trimesters

Key Points The main objective of routine midtrimester ultrasonography (US) is to provide accurate diagnostic information for the delivery of optimised antenatal care, including delivery planning. Routine early US is beneficial because of better estimates of gestational age. Routine US examination leads to earlier detection of clinically unsuspected fetal malformations and earlier detection of multiple pregnancies. Individuals who routinely perform obstetrics scans should have specialised training…

Ultrasound Screening for Fetal Abnormalities in the First Trimester

Key Points Early diagnosis of structural anomalies is increasingly possible. About half of the congenital anomalies can be diagnosed in the late first trimester. Severe and often lethal anomalies can be diagnosed, allowing parents the options of continuing with the pregnancy or, if acceptable, termination of pregnancy. Women appreciate the opportunity of early reassurance or early diagnosis, making this scan an essential first step in screening…

Ultrasound and Biochemical Screening for Fetal Aneuploidy

Key Points First trimester screening for Down syndrome (DS) with a combination of ultrasound, nuchal translucency and two maternal serum markers (combined test) has a much better performance than second trimester screening with four serum markers (quad test). Combined test performance can be improved by the addition of serum markers such as placental growth factor (PlGF) and ultrasound markers such as nasal bone determination. Quad test…

Conveying Information About Screening and Diagnosis

Key Points Good practice in information giving is essential as choosing to have a prenatal screening test can have far-reaching consequences. To be of good quality, information must be up to date and evidence-based. It should as a minimum include the purpose of the test; information about the tested-for condition(s), what the test procedure involves, any risks associated with the test, implications of the possible test…

Principles of Screening

Key Points Screening is the identification of unrecognised disease or defect found by testing an asymptomatic population. Prenatal screening detects conditions that are deleterious to the mother, fetus or both. Prenatal screening allows for diagnostic testing and subsequent pregnancy options, including termination of the pregnancy, preparation for the birth of a child with chronic or fatal illness or the use of advanced reproductive technology to avoid…

Epidemiologic and Research Methods in Fetal Medicine

Key Points The randomised controlled trial (RCT) is the least biased method of assessing the effectiveness of clinical interventions. It has been little used in fetal medicine, but reports are increasing. The details of good clinical trial methodology are now well established. It is critically important to avoid selection bias by ensuring allocation concealment at randomisation. Research synthesis allows the reader to review the totality of…

The Perinatal Postmortem Examination

Key Points Perinatal autopsy (examination after death) fulfils several roles, including determination or clarification of the underlying diagnosis, answering specific questions raised by parents and clinicians, quality assurance, governance and public health aspects, and improved understanding of disease mechanisms through research. Examination after death may involve a spectrum of investigations, including placental pathology, genetic testing, postmortem imaging and internal organ examination or sampling. Parents should be…

Development of the Kidneys and Urinary Tract in Relation to Renal Anomalies

Key Points Development of the kidneys (nephrogenesis) occurs between the 5th and 32nd weeks of human gestation when the ureteric bud interacts with metanephric mesenchyme, which undergoes mesenchymal–epithelial conversion to form glomeruli and tubules and renal stroma, with coordinated vascular development and signalling being critical. Nephron number is the major factor determining long-term kidney function. The development of the nephrons is finalised by the 32nd week;…

Lung Growth and Maturation

Key Points Survival at birth depends upon the lung attaining an adequate size and degree of structural maturity during fetal life. This chapter deals with mechanisms underlying normal and impaired lung growth and lung maturation before birth. The airways of the fetal lung contain a liquid that is actively secreted by the epithelium; this ‘lung liquid’ causes the lung to develop in an expanded state, which…

Development of the Heart and Cardiovascular System in Relation to Cardiac Abnormalities

Key Points The heart is largely derived from mesoderm. A single heart tube forms with venous and arterial connections. It elongates by addition of cells at either end from the surrounding mesenchyme. The tube folds to the right and lies in the pericardial cavity. The atria and ventricles form by ballooning from the tube; septation of the atria and ventricles is largely achieved by this method.…

Placental Pathology and Implications for Fetal Medicine

Key Points Pathological examination of the placenta may provide useful information regarding the underlying mechanisms of a range of pregnancy complications that may guide future management and improve understanding of disease pathophysiology. Placentas should be submitted for examination by specialist pathologists in all complicated pregnancies according to national and local guidelines. Interpretation of the clinical significance of many placental histologic changes remains difficult, and novel approaches…

Placental Function in Maternofetal Exchange

Key Points Maternofetal exchange across the placenta provides the solutes and water needed for fetal development and growth and enables the waste products of fetal metabolism to be transferred to the maternal circulation. The placental exchange barrier consists of the syncytiotrophoblast epithelial cell layer, basement membrane and connective tissue, and the fetal capillary endothelium. All contribute to the barrier, but the syncytiotrophoblast is probably the most…

Development of the Placenta and Its Circulation

Key Points The development and structure of the human haemochorial placenta The development of the uteroplacental and fetoplacental circulations Introduction This chapter highlights areas in which developmental placental biology directly impinges on clinical practice. Pregnancies complicated by the pathologies of stillbirth, severe preeclampsia and intrauterine growth restriction (IUGR), especially those that deliver before 34 weeks, are associated with significant gross and microscopic placental pathology (covered in…

The Immunology of Implantation

Key Points The extravillous pathway of trophoblast differentiation is essential for the development of the fetoplacental blood supply. As they invade into the maternal decidua, extravillous trophoblast cells express a unique array of human leukocyte antigen (HLA) class I molecules, HLA-G, HLA-E and HLA-C. The main population of maternal immune cells in the decidua during placentation are uterine natural killer (uNK) cells. Interaction between polymorphic killer…

Early Pregnancy Failure

Key Points Miscarriage and ectopic pregnancy are the commonest early pregnancy complications. The diagnosis of early pregnancy failure should be made on transvaginal ultrasound scan given its high diagnostic sensitivity and specificity. Sporadic chromosomal abnormalities are the overriding cause of miscarriage. Early pregnancy failure should be managed in a dedicated early pregnancy unit. Management of early pregnancy failure can be expectant, medical or surgical depending on…

Teratology

Key Points At baseline, each pregnancy has a 2% to 4% risk for a congenital anomaly diagnosed at birth. The adverse effects of exposures on embryo-fetal development depend on the agent, dose, and timing of exposure. Resources are available for up-to-date information on specific exposures during pregnancy. Introduction A teratogenic exposure is one that has the ability to interfere with normal development of the fetus. Some…

Staging Embryos in Development and the Embryonic Body Plan

Key Points This chapter presents the concepts and timing of embryonic development. The problems of using staging systems to describe a continuous process are discussed. The method behind staging of animal development is presented. A revision of the timing of early human development is presented. Embryonic and obstetric stages of development are presented. The embryonic body plan, main embryological stages and their approximate times are presented.…

Cellular Mechanisms and Embryonic Tissues

Key Points This chapter describes the tissue types present in early embryos and the interactions between these tissues. The membrane systems and cytoskeletal elements within a typical cell are reviewed. Early embryos contain only epithelial and mesenchymal populations. Each tissue type produces specialised extracellular matrix molecules and proteins which permit and encourage tissue interactions. Specific interactions between developing epithelia and mesenchyme are presented, and the common…

Early Concepts and Terminology

Key Points This chapter considers the language used within embryological research and how it is evolving. The terms used to describe embryos, cells and tissues derive from the social constructs of science during the time they were created. Newer terms have been added as scientific methods have increased, although there may not be a consensus on the definition of some terms. The application of computer sciences…