Fetal blood sampling during pregnancy: risks and diagnostic advantages

A review is provided on the use of fetal blood sampling during pregnancy. Informations on the technique, its indications, risks and benefits are provided. In addition, the application of fetal blood sampling in cases of intrauterine growth retardation as well as some metabolic features of intrauterine life are discussed

The impact of gestational age and fetal growth upon the maternal-fetal glucose concentration difference

Objective: To test whether the human fetus accommodates to the increasing glucose requirements of late pregnancy with an increased maternal-fetal glucose concentration gradient and whether there are differences in pregnancies with fetal growth restriction (FGR) according to clinical severity. Methods: Umbilical venous glucose concentration was measured in 77 normal pregnancies (appropriate for gestational age [AGA]) and 42 pregnancies complicated by FGR at the time of fetal blood sampling. In 40 AGA and in all FGR cases, a maternal 'arterialized' blood sample was collected simultaneously. Growth-restricted fetuses were subdivided into three groups according to fetal heart rate (FHR) recordings and Doppler measurements of the umbilical artery pulsatility index (PI): group I (normal FHR and PI; 12 cases), group 2 (normal FHR, abnormal PI; 17 cases) and group 3 (abnormal FHR and PI; 13 cases). Results: In normal pregnancies with increasing gestational age, there was a significant decrease IP < .001) of umbilical venous glucose concentration and a significant increase of the maternal-fetal glucose concentration difference (P < .001). In addition, there was a significant relation between fetal and maternal glucose concentrations (P < .001). In FGR pregnancies, the maternal-fetal glucose concentration difference was significantly higher in fetuses of groups 2 and 3 compared with normal pregnancies and FGR pregnancies of group 1. Conclusion: In human pregnancy, the fetal glucose concentration is a function of both gestational age and the maternal glucose concentration. In FGR pregnancies, as an accommodation of the fetus to a restricted placental size and placental glucose transport capacity, the maternal-fetal glucose concentration difference is increased, and this increase is a function of the clinical severity

Maternal concentrations and fetal-maternal concentration differences of plasma amino acids in normal and intrauterine growth restricted pregnancies

OBJECTIVES: Our purpose was to determine whether maternal amino acid concentration changes during gestation in pregnancies with intrauterine growth restriction as in normal pregnancies and to verify whether these changes are related to changes in fetal-maternal differences. STUDY DESIGN: Amino acid concentrations were measured in 5 nonpregnant women, in 11 second- trimester and 10 third-trimester pregnant women with appropriate-for- gestational-age fetuses, and in 23 pregnant women with intrauterine growth restriction. Umbilical venous amino acids were measured at the time of fetal blood sampling. The severity of intrauterine growth restriction was assessed by Doppler velocimetry and fetal heart rate and by evaluation of oxygenation and acid-base balance. RESULTS: In normal pregnant women the maternal concentration of most amino acids was significantly lower in both the second and third trimesters compared with nonpregnant women. In intrauterine growth restriction the maternal concentrations of most essential amino acids were significantly higher than in appropriate-for-gestational-age pregnancies. This observation, coupled with lower fetal amino acid concentrations in intrauterine growth restriction, leads to significantly lower fetal-maternal differences. CONCLUSIONS: Normal pregnant women have a significant decrease in amino acid concentrations compared with nonpregnant women, whereas in intrauterine growth restriction maternal amino acids are reduced less. Significantly lower fetal-maternal concentration differences are present in intrauterine growth restriction, independent of the degree of severity

In vivo placental transport of glycine and leucine in human pregnancies.

L-[1-13C]Glycine and L-[1-13C]leucine were infused as a bolus into 12 pregnant patients carrying normal fetuses before fetal blood sampling at gestational ages ranging from 20 to 37 wk. Maternal venous samples were obtained every 2-3 min for 15 min after the bolus infusion. Fetal samples were obtained from the umbilical vein within 15 min of the bolus. Amino acid plasma enrichments (molar percent enrichment) were determined by gas chromatography-mass spectroscopy and their concentrations by ion exchange chromatography. The ratios of glycine and leucine transfer were assessed from fetal/maternal enrichment ratios for each amino acid. We now report that over the gestational age range of 20-37 wk, under relatively undisturbed fetomaternal conditions (fetal blood sampling), human placental glycine transfer is limited, with a glycine/leucine ratio = 0.16 \ub1 0.02. We hypothesize that, in human pregnancies, the relative rates of in vivo transplancental transport of amino acids can be assessed indirectly utilizing fetal blood sampling and stable isotope methodology. The application of this approach to leucine and glycine demonstrates that the transfer of leucine is rapid (demonstrable in seconds), whereas that of glycine is more limited