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Families with birth defects: is birth weight of nonmalformed siblings affected?
Kari Klungsøyr Melve1, Rolv Skjaerven
1Section for Medical Statistics, Department of Public Health and Primary Health Care, University of Bergen, Norway. Kari.Melve@isf.uib.no
Insights
Congenital malformations in infants are linked to lower birth weight, but this reduction is specific to the affected pregnancy. Non-malformed siblings of affected infants do not show significantly different birth weights compared to those in unaffected families.
Area of Science:
- Perinatal epidemiology
- Medical genetics
- Public health
Background:
- Infants with congenital malformations typically exhibit lower birth weights.
- Recurrence of preterm delivery and low birth weight within families is a known phenomenon.
Purpose of the Study:
- To compare birth weights of siblings of malformed infants with those in unaffected families.
- To investigate if reduced birth weight associated with congenital anomalies affects non-malformed siblings.
Main Methods:
- Utilized data from the Medical Birth Registry in Norway (1967-1998).
- Linked births to mothers via unique personal identification numbers to create sibship files.
- Grouped families based on the presence and birth order of congenital malformations.
Main Results:
- Non-malformed siblings of infants with congenital malformations showed no significant difference in mean birth weight compared to infants in unaffected families.
- The malformed infant itself had a significantly reduced birth weight.
- Adjusted analyses confirmed these findings, indicating the effect is specific to the affected pregnancy.
Conclusions:
- Reduced birth weight in infants with congenital anomalies is specific to the pregnancy with the malformation.
- The findings suggest that congenital malformations do not inherently impact the birth weight of subsequent non-malformed siblings.
Abstract:
Infants with congenital malformations have on average lower birth weight than do infants without malformations. Preterm delivery and low birth weight are known to recur in sibships. The aim of the study was to compare the birth weight of siblings to malformed infants with the birth weight of infants in families without malformed infants. Data were from the Medical Birth Registry in Norway from 1967 to 1998. Births were linked to their mothers through the unique personal identification number, providing sibship files with the mother as the observation unit. The study was based on 551,478 mothers with at least two singleton infants and 209,423 mothers with at least three singletons. The authors grouped the families according to whether and in which birth order an infant had a registered congenital malformation and compared birth weight and gestational age between infants of the same birth order in families with malformations and without. Overall, in families where one or two infants had a congenital malformation, the crude and adjusted mean birth weight of nonmalformed siblings did not differ from that of infants in unaffected families, whereas it was significantly reduced for the malformed infant itself. We conclude that reduced birth weight associated with congenital anomalies is specific to the affected pregnancy.