Nearly, two thirds of all pregnancies are affected by serious abnormalities which lead to spontaneous abortion in the first 3–4 weeks of gestation, often before the pregnancy has been confirmed. Half of these have a chromosomal abnormality. Almost 10 % of pregnancies abort in the embryonic stage, from inborn errors of metabolism or gross malformations. The surviving fetuses now represent about 30 % of the original number of fertilized ova, but a few still harbour a defect such that 3–4 % of babies born have an abnormality (Fig. 2.1).

There are four main groups of congenital lesions: inborn errors affecting the fertilized ovum, ­abnormalities occurring at the time of the three germ layers, abnormalities of organogenesis and defects in fetal movement or compression (Fig. 2.2). Genetic or chromosomal anomalies are present from the one-cell stage, and cellular or germ layer defects occur between 1 and 3 weeks after conception. These two groups account for the enormous drop in survival during the early weeks of pregnancy. Only a small percentage of conceptuses with these defects survive to birth. Between three and 10 weeks’ gestation, the basic shape and organs of the embryo form and this is when most surgical malformations arise. Anomalies occurring during embryogenesis may be caused by innate genetic defects or by extrinsic teratogens (e.g. rubella or other congenital infections, x-rays, drugs, chemicals or maternal dietary abnormalities).

Knowledge of the causation of many surgical malformations is poor because the embryonic stage is the most difficult phase of pregnancy to study. Despite this limitation, there are several important principles of surgical anomalies which are essential if the clinical situation at birth is to be understood:

Yes! Where one major anomaly is observed, the presence of others must be sought. Dysmorphism may indicate that the child has a number of malformations which may be well enough known to be called a ‘syndrome’. A syndrome is a collection of features or defects which is recognized as belonging to the one entity. Individual syndromes are rare and may carry unwieldy eponymous names which make them an anathema to the average student or clinician, although obsessive/compulsive learners seem drawn to them. Their real importance is that definitive diagnosis of the syndrome will allow other features of the syndrome not yet identified to be actively sought, usually after consultation with a geneticist or database. Moreover, the prognosis will be predicted more readily than in complex cases without recognized syndromes, since outcome usually has been well defined by previously reported cases. This information is essential in the perinatal period so that the parents can be given a realistic outline of the future. The inevitable fatality of certain syndromes may enable proper discussion about the most appropriate treatment to be offered. In many cases, accurate syndrome identification also permits the cause and risk to future pregnancies to be determined. This can be supported by specific tests in some cases where the genetic defect leading to the syndrome has been identified.

The principles required by the average clinician are simple, although consultation with an expert colleague is advisable for confirmation. Where a baby has several obvious malformations, the clinician should be alerted to the possibility of a syndrome being present and seek further evidence of this. The areas of the body in which minor abnormalities occur frequently are easily accessible in the neonate and should be carefully scanned (Fig. 2.4). Facial features obviously need to be assessed in the context of the appearance of the parents. Minor anomalies are important because their presence has a strong correlation with the existence of major malformations.

The finding of a number of minor anomalies in addition to major defects adds weight to the possibility that a syndrome is present.

It is important that the clinician is not daunted by a lack of detailed knowledge of individual syndromes. A search for time-related internal defects, space-related defects and minor anomalies of the face and hands will usually yield significant information, even when performed by inexperienced examiners.