Reduction of soft tissue deposition in normal triplets

In a previous study, birth weight projections obtained with Rossavik growth models were systematically greater than actual birth weights in triplets but not in singletons. To investigate the cause of this overestimation, average mean percent deviations for head circumference (HC), abdominal circumference (AC), thigh circumference (ThC), and weight (WT) at different times in the third trimester were studied in 13 normal triplet and 20 normal singleton fetuses using individual growth curve standards. Average mean percent deviation values for HC in both singletons and triplets were close to zero throughout the third trimester. Average mean percent deviation values for AC in both singletons and triplets were similar, and remained relatively constant. Average mean percent deviation values for ThC in triplets decreased toward the end of the third trimester, but those for singletons increased. Average mean percent deviation values for estimated weight did not change during the third trimester in singletons whereas those in triplets decreased. The difference in average mean percent deviation values for estimated weight between singletons and triplets in the 32- to 36-week interval was statistically significant. There were no significant differences between actual and predicted measurements for HC in both singletons and triplets at birth. However, actual birth measurements were systematically less than predicted birth measurements for AC and ThC in singletons, and for AC, ThC, and WT for triplets. These systematic differences were significantly larger in triplets for ThC and WT. Nutrition Score values, direct measures of subcutaneous tissue, were significantly lower in triplets compared to singletons.(ABSTRACT TRUNCATED AT 250 WORDS)