Angiodysplasias of the umbilical cord vessels have been little studied though they are an interesting and important aspect of foetal development. For example, when the vein and arteries are not of regular length, loops and kinks can form within them, usually in the vein, and these appear as knots in the cord within the Wharton jelly. They are known as false knots (Fig. 2.8) and are thought to have no clinical significance though, in fact, if the phlebectasia is significant and microthrombi form within the vein, these may arrive at the foetal heart [9].

Similar to the false knots which are circumscribed venous ectasias, there can also be a widespread phlebectasia in a varicose condition of the umbilical vein (Fig. 2.9) where repetitive significantly important phlebectasias can increase the probability of endovascular thrombosis. The vascular damage is limited to the part of the wall where the muscle layer is too thin without compensating elastic fibre or fibrous material. Unlike in the lower limbs, there is no inflammatory aspect so rendering the situation much less dangerous. Analogous aneurysmatic dilations of the arteries are much rarer.

A careful programme of coloration of the various parts of the funicular artery walls must be utilised to be able to identify the lesions (Fig. 2.10). The correct histochemical staining will identify the elastic components of the walls and the elastic layers and also the components of hyaluronic acid, collagen and acid or neutral polysaccharide mucins. Immunohistochemical staining with smooth muscle actin antibodies and desmin antibodies is indispensable to see the myofibroblasts and smooth muscle cells of the intima and the tunica media. In this way a series of elementary lesions can be identified which can be ascribed to four conditions.

The first of these is a hypertrophy of the intima which is not usually circumferential but involves only a segment of the internal circumference and is a proliferation of smooth muscle cells and myofibroblasts. The second condition is a concentric hypertrophy of the tunica media due to hyperplasia of the smooth muscle cells. The third is a non-muscular thickening of the wall from the tunica media due to reactive fibrosis and an increase of the collagen and elastic components. The fourth and last condition is a degeneration of the tunica media with a reduction in elastic fibres, delamination of the smooth muscle bundles and an accumulation of mucopolysaccharide acids and particularly hyaluronic acid. The lack of information in the literature, other than some case studies, does not allow any analysis or correlation with genetic diseases; however, it is clear that vascular lesions of this type cannot but reflect a pathology in placental circulation and, at the same time, indicate possible actual or latent similar alterations in the foetal circulatory system.

Unlike the vasculopathies of the previous paragraph, inflammations of the umbilical cord have been widely studied by clinicians and researchers. They can be associated or not with inflammation of the Wharton jelly including various types of funisitis. Inflammations of the umbilical cord are as a rule associated with a pervasive and serious chorioamnionitis. More frequently the problem is with the vein than with the arteries, probably due to two factors, the first being in the different histological characteristics of the two typologies of vessel with the arterial walls having an intrinsic resistance while the vein walls are much more vulnerable and the second being that the blood flows from the placental chorioamniotic structures to the foetus, indicating a progression gradient of diffusion and extension of inflammation and therefore indirectly of infection. Arterial inflammation may indicate an advanced infection of the cord vessels, but more likely it is a sign of a massive colonisation of the foetus itself, with the infection now being brought from the foetus in the blood flow towards the placenta. Bacterial agents are essentially responsible for cord vasculitides, most of which are common germs such as staphylococchi, streptococchi, Ureaplasma urealyticum, Escherichia and Enterobacteriaceae, while in the case of many chorioamnionitic and vascular infections, the causal agent cannot be identified, as is also the case in inflammatory states of the membranes. Except in extremely serious infections, the neonatal outcome does not depend on the seriousness of the lesion nor on its extent in any way. Many chorioamnionitic infections are reported in neonates without any clinical problems. However, there are times when the inflammation is correlated to an unfavourable or critical clinical progression and the guidelines for the prevention of perinatal streptococcal disease must be scrupulously followed. Additionally, it can happen that an inflammatory state of the vein is established in a condition of angiodysplasia or vasculopathy, in which case there is a significant increase in risk of thrombosis inside the phlebectasia and/or dysplasia.

This condition is present in an imprecise number of pregnancies, thought to be about 0.5–1.0 %; however, in a series of foetal malformation, the condition has been reported at 8.7–46 %, leading many authors to consider a missing artery as a marker for other congenital abnormalities. The artery could be missing because it was never originally formed or because it was absorbed after formation owing to a preponderance of flow in the other artery. This second hypothesis can be confirmed by findings of remains of smooth muscle fibres along the cord. Malformations which can induce the reabsorption of an artery are those connected to the abdominal wall such as hernia, persistent urachus, bladder exstrophy, etc. or those of the urinary apparatus with a consequent destruction of the part of the abdominal wall where the artery passes through. In the case of sirenomelia, where there is hypoplasia of the lower half of the body with fused legs and anogenital defects, we find the lack of formation of the umbilical arteries from the allantoid vessels with a single cord artery coming directly from the abdominal aorta below the superior mesenteric artery as an evolution of the primitive omphalomesenteric artery.

When the umbilical cord is abnormally positioned relative to the chorionic plate (Fig. 2.11) either marginally (Fig. 2.12) or even on the membranes (velamentous insertion) (Fig. 2.13), the blood vessels must run abnormally to reach their cotyledons. Such abnormalities can create critical conditions for placental circulation and thus for the foetus. In a velamentous cord insertion, the vessels run not in straight lines but freely over the membranes reaching lengths of 20–30 cm, even arriving at the opposite margin of the placenta. On some occasions they form minor branches that can have larger diameters than the original. Clearly, during foetal engagement or labour, a vessel can rupture and cause sudden and massive foetal exsanguination and death [10, 11]. Less dramatically, compression of these vessels can create stop and go alterations in blood flow with repercussions on the flow rates of the cord vessels and thus foetal perfusion, especially serious for the intracranial and cerebral regions. The incidence of velamentous insertion is higher in twin pregnancies, and therefore the risk is higher for anomalous conditions of the chorionic vessels. These conditions are more serious in twin pregnancies with fused placentas, whether monochorionic diamniotic or dichorionic diamniotic, as, at the dividing membrane, the vessels, unprotected by Wharton’s jelly, are more susceptible to pressure or squeezing by one or both of the twins.

Abnormal or unusual routes of the blood vessels on the chorionic surface (Fig. 2.14) are not limited to markedly eccentric or marginal cord insertion. Even when the cord is centrally inserted in a single placenta, routes can be complex and tangled. Vessels, both arteries and veins, can be found touching, crossing, overlapping or even plaited together, and at times dystrophic alterations of the walls can be observed. Clearly, in these conditions, narrowing takes place and bottlenecks are formed so altering blood flow.

Dysplasia of the walls of both veins and arteries can occur. In the veins we may observe ectasia either limited to small tract or extended to varicosity with a sudden increase of vessel calibre. As in the case of the funicular vessels, such lesions can give rise to wall thrombi just as can all phlebectasias or varicose states of the adult. These lesions may create a critical situation especially if associated with an inflammatory state of subamniotic or perivascular connective tissue (on the foetal side of the chorionic plate).