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Follow-up study of physical growth of monozygous twins with discordant within-pair birth weights
Insights
Intrauterine growth-retarded twins often achieve normal growth by age 30 months. However, birth weight below the tenth percentile may indicate persistent growth issues, influenced by factors like child-rearing differences.
Area of Science:
- Pediatrics
- Neonatology
- Human Growth and Development
Background:
- Intrauterine growth retardation (IUGR) affects fetal development, leading to varied birth weights even in identical twins.
- Understanding long-term growth trajectories of IUGR infants is crucial for clinical management.
Purpose of the Study:
- To investigate the long-term growth patterns of monozygous twins with significant birth weight discordance.
- To identify factors influencing catch-up growth in smaller, growth-restricted twins.
Main Methods:
- Prospective follow-up of 14 monozygous twin pairs with birth weight differences (11%-48%).
- Bi-annual measurements of weight, length, and head circumference for 3 years, then annually up to 9 years.
- Analysis of growth concordance and identification of growth-retarded individuals.
Main Results:
- Significant within-pair birth weight, length, and head circumference differences at birth.
- Insignificant differences in head circumference, length, and weight by 12, 24, and 30 months, respectively.
- Most catch-up growth occurred within the first two years; however, some smaller twins remained growth-retarded.
Conclusions:
- While many twins with IUGR achieve normal growth, persistent deficits can occur, especially if birth weight is below the tenth percentile.
- Environmental factors, such as child-rearing, can impact growth outcomes.
- A normal ponderal index in smaller twins was associated with poorer growth outcomes in this cohort.
Abstract:
In an attempt to determine the future growth of intrauterine growth-retarded babies, 14 pairs of monozygous twins, showing within-pair birth weight differences of 11% to 48% (median 28%), were followed prospectively for 3 to 9 years. Weight, length, and head circumference were measured biannually for the first 3 years of life and thereafter annually. At birth, the median within-pair percentage differences of weight (28%), length (6.2%), and head circumference (5.2%) were all significant (P less than .01). At 12, 24, and 30 months of age, these median within-pair percentage differences became insignificant for head circumference, length, and weight, respectively. The most rapid catch-up growth of the lighter twins occurred during the first 2 years of life. Analysis of individual pairs, however, showed suboptimal growth in both members of two pairs, although growth became concordant. In four other pairs, the lighter birth weight member remained growth retarded in comparison with the cotwin and showed within-pair differences in weight varying between 8% and 19%, in height between 1% and 6%, and in head circumference between 1.9% and 7%. All children with birth weights above the tenth percentile grew up normally, regardless of the extent of within-pair birth weight differences, with one exception. This exception was a pair in whom there were within-pair differences in child rearing. In the six pairs in which the smaller twin's birth weight was below the tenth percentile, only three pairs showed normal growth. In these six pairs a normal ponderal index in the lighter twin members was associated with poorer growth than a low ponderal index.(ABSTRACT TRUNCATED AT 250 WORDS)