Increasing fetal ovine number per gestation alters fetal plasma clinical chemistry values

Abstract

Intrauterine growth restriction (IUGR) is interconnected with developmental programming of lifelong pathophysiology. IUGR is seen in human multifetal pregnancies, with stepwise rises in fetal numbers interfering with placental nutrient delivery. It remains unknown whether fetal blood analyses would reflect fetal nutrition, liver, and excretory function in the last trimester of human or ovine IUGR In an ovine model, we hypothesized that fetal plasma biochemical values would reflect progressive placental, fetal liver, and fetal kidney dysfunction as the number of fetuses per gestation rose. To determine fetal plasma biochemical values in singleton, twin, triplet, and quadruplet/quintuplet ovine gestation, we investigated morphometric measures and comprehensive metabolic panels with nutritional measures, liver enzymes, and placental and fetal kidney excretory measures at gestational day (GD) 130 (90% gestation). As anticipated, placental dysfunction was supported by a stepwise fall in fetal weight, fetal plasma glucose, and triglyceride levels as fetal number per ewe rose. Fetal glucose and triglycerides were directly related to fetal weight. Plasma creatinine, reflecting fetal renal excretory function, and plasma cholesterol, reflecting placental excretory function, were inversely correlated with fetal weight. Progressive biochemical disturbances and growth restriction accompanied the rise in fetal number. Understanding the compensatory and adaptive responses of growth-restricted fetuses at the biochemical level may help explain how metabolic pathways in growth restriction can be predetermined at birth. This physiological understanding is important for clinical care and generating interventional strategies to prevent altered developmental programming in multifetal gestation.

Keywords: Fetal; nutrition; ovine; placenta.

Figure 1

Growth Parameters at GD130 on the vertical axis were examined based on fetal number per ewe with S (singletons blue), Tw (twins red), Tr (triplets green), and Q (quadruplets/quintuplets purple) on horizontal axis. Error bars represent Means ± SEM. Lower case letters indicate post hoc differences (s from singletons, tw from twins, tr from triplet, and q from quadruplets/quintuplets). Regression lines follow the same color scheme; S in squares, Tw in circles, Tr in triangles, and Q in diamonds. (A) Placentomes; as fetal number per ewe increased, a stepwise fall in placentome number was seen, P < 0.001. (B) Fetal Weight (kg); as fetal number per ewe increased, a stepwise fall in fetal weight was seen, P < 0.0001. Samples sizes were 14 singletons, 45 twins, 34 triplets, and 8 quadruplets+. (C) Fetal Kidney Weight (g); as fetal number per ewe increased, a stepwise fall in fetal kidney weight was seen, P < 0.0001. Sample sizes were 18 singletons, 58 twins, 42 triplets, and 14 quadruplets+. D. Fetal Kidney Weight (g) and Fetal Weight (kg). Kidney weight was directly related to fetal weight, P < 0.0001. (E) Fetal Liver Weight (g); as fetal number per ewe increased, a stepwise fall in fetal liver weight was seen, P < 0.0001. Sample sizes were 16 singletons, 56 twins, 42 triplets, and 14 quadruplets+. (F) Fetal Liver Weight (g) and Fetal Weight (kg). Liver weight was directly related to fetal weight, P < 0.0001. (G) Fetal Brain Weight (g) Relative to Fetal Weight (kg); Fetal brain weight was relatively spared, with stepwise increase observed when expressed relative to fetal weight, P < 0.0001. Sample sizes were 16 singletons, 52 twins, 40 triplets, and 8 quadruplets+. (H) Fetal Brain Weight (g) and Fetal Weight (kg). Brain weight was directly related with fetal weight, P < 0.0001.

Figure 2

Macronutrients and Minerals at GD130 on the vertical axis were examined based on fetal number per ewe with S (singletons blue), Tw (twins red), Tr (triplets green), and Q (quadruplets/quintuplets purple) on horizontal axis. Error bars represent Means ± SEM. Lower case letters indicate post hoc differences (s from singletons, tw from twins, tr from triplet, q from quadruplets/quintuplets). Regression lines follow the same color scheme, S in squares, Tw in circles, Tr in triangles, and Q in diamonds. (A) Fetal Plasma Glucose levels (mg/dL); as fetal number per ewe increased, a stepwise fall in glucose was seen, P < 0.0001. Sample sizes were 18 singletons, 58 twins, 42 triplets, and 8 quadruplets+. (B) Plasma Glucose Levels (mg/dL) and Fetal Weight (Kg). Glucose was directly related to fetal weight, P < 0.0001. (C) Fetal Plasma Triglyceride levels (mg/dL); triglyceride differed, with lowest values in quads/quints, P < 0.0015. Sample sizes were 18 singletons, 58 twins, 40 triplets, and 8 quadruplets+. (D) Fetal Plasma Triglyceride levels (mg/dL) and Fetal Weight (kg). Plasma triglyceride was directly proportionate to fetal weight, P < 0.005. (E) Fetal Plasma Alkaline (Alk) Phosphatase levels (U/L); Alk Phosphatase was lower in triplets and quadruplets/quintuplets than other groups, P < 0.002. Sample sizes were 18 singletons, 58 twins, 42 triplets, and 8 quadruplets+. (F) Fetal Alk Phosphatase levels (U/L) and Fetal weight (kg). Alk Phosphatase was directly proportionate to fetal weight, P < 0.01.

Figure 3

Liver Enzymes at GD130 on the vertical axis were examined based on fetal number per ewe with S (singletons in blue), Tw (twins red), Tr (triplets green), and Q (quadruplets/quintuplets purple) shown on the horizontal axis. Error bars represent Means ± SEM. Letters indicate post hoc differences from other groups (s from singletons, tw from twins, tr from triplets, q from quadruplets/quintuplets). Regression lines follow the same color scheme; S in squares, Tw in circles, Tr in triangles, and Q in diamonds. (A) Fetal Plasma AST levels (U/L); AST was increased in quadruplets/quintuplets, P < 0.0001. Sample sizes were 14 singletons, 56 twins, 42 triplets, and 14 quadruplets+. (B) Fetal Plasma AST levels (U/L) and Fetal Weight (kg). AST was not related to fetal weight. (C) Fetal Plasma LDH levels (U/L); LDH was lower in triplets and quadruplets/quintuplets, P < 0.0001. Sample sizes were 14 singletons, 56 twins, 36 triplets, and 14 quadruplets+. (D) Fetal LDH levels (U/L) and Fetal weight (kg). LDH was directly related to fetal weight (kg), P < 0.025.

Figure 4

Placental and Fetal Excretory Function at GD130 on the vertical axis was examined based on fetal number per ewe with S (singletons in blue), Tw (twins in red), Tr (triplets in green), and Q (quadruplets/quintuplets in purple) shown on the horizontal axis. Error bars represent Means ± SEM. Letters on bar graphs indicate post hoc differences from other groups (s = differs from singletons, tw = differs from twin, tr = differs from triplet, q = differs from quad group). Regressions of growth parameters use the same color scheme, inset with S in squares, Tw in circles, Tr in triangles, and Q in diamonds. (A) Fetal Plasma Cholesterol levels (mg/dL); as fetal number per ewe increased, cholesterol rose, P < 0.0001. Sample sizes were 18 singletons, 58 twins, 42 triplets, and 8 quadruplets+. (B) Plasma Cholesterol Levels (mg/dL) and Fetal Weight (kg). Cholesterol was indirectly related to fetal weight, P < 0.0001. (C) Fetal Plasma Blood Urea Nitrogen (BUN) levels (mg/dL); as fetal number per ewe increased to triplets, BUN rose slightly, P < 0.015, with post hoc differences shown. Sample sizes were 18 singletons, 58 twins, 30 triplets, and 8 quadruplets+. (D) Fetal Plasma BUN levels (mg/dL) and fetal weight (kg). BUN was inversely related to fetal weight, P < 0.001. (E) Fetal Plasma Creatinine levels (mg/dL); as fetal number per ewe increased, creatinine rose, P < 0.0001. Sample sizes were 18 singletons, 58 twins, 30 triplets, and 8 quadruplets+. (F) Creatinine Levels (mg/dL) and Fetal Weight (mg/dL). Creatinine was inversely related to fetal weight, P < 0.0001. (G) Ratio of Fetal:Maternal Plasma BUN; although minimal change was appreciated by fetal number, (H) Ratio of Fetal:Maternal Plasma Creatinine rose, P < 0.0001.