Pregnancy plasma amino acid concentrations

Plasma amino acid concentrations are high during the first days of life, especiaUy in premature neonates, but they tend to be low in infants with birth weights low for their gestational age because of placental insufficiency. Maternal values are low in the first half of pregnancy. In adults, increased plasma levels of homocysteine have been hnked to increased risk of heart disease (see Chapters 26 and 44). ... 

Table 13.5 Plasma amino acid concentrations during pregnancy in unaffected women (pmol/L) [7]...

Maintain Plasma Amino Acid Concentrations Within the Normal Range and Anticipate a Higher Intact Protein Tolerance as Pregnancy Progresses... 

Plasma amino acid concentrations were monitored one to two times per week. Goals for the pregnancy included maintaining leucine and isoleucine concentrations between 100 and 300 tmol/L and valine concentrations between 200 and 400 pmol/L. Prealbumin, albumin, and... 

Blood concentrations of many amino acids decrease as pregnancy progresses with the increase in placental uptake and other changes in matemal/fetal metabolism [23]. Normal values for pregnancy need to be considered in interpretation of plasma amino acid profiles. Plasma amino acids need to be monitored frequently, and, if low, an increase in the amount of intact protein is prescribed to maintain the restricted amino acids in the normal range. 

Because of increases in plasma volume and cardiac output, renal blood flow increases. The GFR ri.ses early in pregnancy, and creatinine clearance may be 150 ml/min or more by. 10 weeks. Serum urea and creatinine concentrations fall. Tubular function alters and. in particular, there is a reduction in the renal threshold for glucose. Glycosuria may be present in up to 70% of pregnancies. Tubular reabsorption of uric acid and amino acids alters, and their excretion in urine increases. 

Overrestriction of amino acids may contribute to the poor fetal growth that has been noted in the second and third trimester in MSUD and MMA pregnancies [1, 12]. If a single amino acid is supplemented as part of treatment, additional supplementation may be required to prevent low plasma concentrations, even with the increase in intact protein tolerance as pregnancy progresses. 

The patient was able to restart medical food by 12 h after delivery, and by postpartum day 2, she was consuming as much medical food as she consumed at the end of pregnancy. Leucine levels remained within the normal range. Thus, she was weaned off of parenteral solutions over a 2-day period, and her leucine prescription was incrementally increased to her prepregnancy leucine prescription of 550 mg/day. However, her plasma leucine began to increase on Day 5 after delivery, so intact protein was removed from the diet, and additional energy was provided by reintroduction of IV dextrose and lipid solutions. However, the plasma leucine continued to increase. It was only after reintroduction of protein from the BCAA-free parenteral amino acid solution that the plasma leucine concentration decreased. On Day 6,... 

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