Folic acid supplementation.

Neural tube defects represent one of a limited number of congenital conditions for which primary prevention strategies are available. Despite strong clinical evidence to support the preventive effect of supplementary folic acid given prior to conception and continued throughout the first 12 weeks of pregnancy, there is limited recent epidemiological data to support the effectiveness of national folic acid supplementation programs. Whether folic acid fortification of staple foods will provide a more effective means of achieving further reductions in the prevalence rates for this condition remains open to question. Recent advances associating folic acid supplementation, hyperhomocysteinaemia and neural tube defects provide a new insight into the possible pathological mechanism of this and possibly other related congenital conditions.

The obstetric experience of carriers of haemophilia.

OBJECTIVE: To review the obstetric problems, pregnancy outcome and management of carriers of haemophilia. DESIGN: Retrospective review of haemophilia and maternity unit records. SETTING: Haemophilia Comprehensive Care Centre. PARTICIPANTS: Thirty-two carriers of haemophilia (24 haemophilia A, eight haemophilia B) who had their obstetric care at the Royal Free Hospital over a 10-year period (1985-1995). MAIN OUTCOME MEASURES: Uptake and results of prenatal diagnosis, changes in factor levels during pregnancy, effect of knowledge of fetal gender on obstetric management and neonatal outcome, and maternal haemorrhagic complications. RESULTS: There were 82 pregnancies and 32 resulted in miscarriage or social abortion. The option of prenatal diagnosis was taken up in only 35% (17/48) of pregnancies. There were five affected male fetuses diagnosed prenatally but only three women opted for termination of the pregnancy. Knowledge of fetal gender was unavailable to the attending obstetrician in 46% (21/46) of pregnancies. A fetal scalp electrode was applied in eight, fetal blood sampling was performed in four, and ventouse delivery was conducted in one of these pregnancies. No adverse effects were reported from the first two procedures, but the ventouse delivery was associated with a huge cephalhaematoma requiring blood transfusion. On the other hand, in five cases fetal blood sampling was withheld because fetal gender was unknown. Four of the eight caesarean sections performed might have been avoided if the gender had been known. The incidence of primary and secondary postpartum haemorrhage was high, 22% (including two cases with massive haemorrhage) and 11%, respectively. CONCLUSION: Carriers of haemophilia A and B require special obstetric care with close liaison with the haemophilia centre, and management guidelines should be available and observed. Knowledge of fetal gender is very valuable for management in labour and should be determined antenatally even if the mother declines prenatal diagnosis.

Metabolic and endocrine findings in appropriate and small for gestational age fetuses.

The oxygenation and metabolism in appropriate (AGA) and small for gestational age (SGA) fetuses has been investigated by cordocentesis. The umbilical venous and arterial pO2 and pH decrease with gestational age while pCO2 increases and blood lactate concentration does not change. The mean umbilical venous blood glucose concentration is higher than in the umbilical artery indicating that there is fetal glucose uptake from the placenta. Similarly, the maternal glucose concentration is higher than the fetal and the levels in the two compartments are significantly correlated. The plasma insulin concentration increases exponentially with gestation reflecting the progressive maturation of the fetal pancreas. The fetal plasma cortisol does not change but the fetal plasma ACTH increases with gestation. Fetal plasma triglyceride concentration decreases exponentially with gestation and this is likely to be the result of increased utilization by the fetus for deposition into adipose tissue. There is a high correlation between fetal and maternal levels for individual amino acids and the concentration in the fetus is higher than in the mother, supporting the active transport of amino acids by the placenta. Some SGA fetuses are compromised by hypoxemia, hypercapnia, hyperlacticemia and acidosis, are starved of glucose and amino acids, and are hypertriglyceridemic. Furthermore, some of these fetuses are hypoinsulinemic and the degree of hypoinsulinemia is disproportional to the degree of hypoglycemia suggesting pancreatic dysfunction. In SGA fetuses the plasma cortisol is increased and the plasma ACTH decreased. Knowledge of human fetal oxygenation and metabolism may help in deciding the optional timing of delivery but may also constitute a basis for future fetal therapy in the form of oxygen and nutrient supplementation.