**5. Conclusion**

We studied a group of 53 fetuses with malformations of varying clinical expression and severity, and measured in the fetal blood essential biochemical parameters which may be associated with fetal well-being; the results obtained were compared with those from a group of 73 fetuses with normal growth and morphology.

The disparity in the populations studied make the interpretation of the results difficult. Around 20% of the pathological pregnancies are accompanied by a state of fetal distress with acid-base balance alterations. Gaseous acidosis is present in the cardiac malformations; acidosis is mixed in the malformations of the central nervous system and pulmonary malformations, and is essentially metabolic in the case of fetoplacental anasarca.

The gasometric anomaly most frequently encountered is hypoxemia, present in around 40% of observations and in almost all types of pathology.

The reduction in the umbilical venous pO2 probably reflects an impaired transplacental transfer of respiratory gases and placental dysfunction; it may also be related to a maternal cause (such as an episode of hypoxemia), or a properly fetal cause such as fetal anemia.

Metabolic anomalies, often less common, are associated with acid-base anomalies. The decrease in umbilical venous glucose, found in 18% of the pathologies studied, leads to a suspicion of a reduced transplacental passage of glucose, in parallel to the reduced diffusion of oxygen.

Conversely, the umbilical venous hyperglycemia present in some cases, is secondary to a maternal hyperglycemia and probably associated with a diabetic or pre-diabetic state in the mother.

Changes to concentrations of lactate, free fatty acids, ketone bodies and cholesterol are markers of a disrupted fetal metabolism. Hyperlactatemia is associated with impaired oxygenation conditions and inadequate placental clearance.

The reduction in umbilical venous cholesterolemia found in some pregnancies reflects defective metabolic conditions in the fetus. It has possible consequences on fetal growth and is possibly linked to the morphological anomalies found, with cholesterol being an essential constituent for the development of the embryo.

The results obtained are however a reflection of an instantaneous measurement and the biochemical anomalies found may be a consequence of the malformations.

Moreover, in nearly 50% of cases, the blood chemistry and the in utero living conditions of the fetus with congenital malformations are not very disrupted compared with those of the normally constituted fetus.
