MATERNAL VOLUME HOMEOSTASIS IN EARLY-PREGNANCY IN RELATION TO FETAL GROWTH RESTRICTION

Objective: To test the hypothesis that volume adaptation in pregnancie s complicated by fetal growth restriction (FGR) is already abnormal ve ry early in pregnancy. Methods: In six pregnancies later complicated b y FGR, volume homeostasis in the first 8 weeks was compared to that in ten normal pregnancies. Creatinine clearance, volume-dependent hormon es, hemodilution-related variables, and ultrasonic cardiovascular dime nsions were measured weekly between weeks 5 and 10, in the second and third trimesters, and postpartum. Differences between the two groups w ere analyzed by nonparametric tests. Results: Very early in pregnancy, pregnancies complicated by FGR differed from normal pregnancies in th e following ways: smaller left atrial diameter, smaller collapsible pa rt of the inferior vena cava, lower serum sodium concentration, and sm aller fall in serum creatinine and urea. Conclusion: Fetal growth rest riction is preceded by defective volume adaptation very early in pregn ancy. It appears that the maternal compensation mechanisms are unable to resolve the transient state of vascular underfill seen in this peri od in normal gestation.