Twin birth weight standards.
OBJECTIVE
The aim of this study was to present customized twin-specific birth weight standards. The relative contribution of gestational age, maternal factors, twin factors and placental factors to the birth weight was evaluated in a multivariate approach.


METHODS
Perinatal data were obtained from 10,177 live-born twins from the East Flanders Prospective Twin Survey. Of 8,454 twins (4,227 pairs), of whom all data were available, the birth weights at different gestational ages were analyzed using a non-linear multivariate gaussian regression.


RESULTS
All considered covariates influenced birth weight of twins significantly, with the exception of sex of the co-twin and mode of conception and delivery. At 37 weeks of gestation, a difference of >1 kg existed between favourable and adverse prenatal environment. Up to 40 weeks, sex, site of the umbilical cord, parity, and birth order had a greater influence on birth weight than zygosity, chorionicity and fusion of the placentas. From 34 weeks on, the birth weight of the second-born twin deviated and after 40 weeks, birth weight of monozygotic monochorionic twins dropped, while the other twins continued to grow.


CONCLUSIONS
Customized twin-specific birth weight standards, which take these covariates into account, offer the opportunity for a better assessment of the influence of birth weight of the twin on neonatal health in future research. Already the Developmental Origins of Health and Disease hypothesis showed that these prenatal conditions might also be important for the follow-up of the twin.
Gielen
Marij
M
Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Department of Population Genetics, Genomics and Bioinformatics, Maastricht University, Maastricht, The Netherlands. marij.gielen@gen.unimaas.nl
Lindsey
Patrick J
PJ
Derom
Catherine
C
Loos
Ruth J F
RJ
Derom
Robert
R
Nijhuis
Jan G
JG
Vlietinck
Robert
R
D001724:Birth Weight; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D011446:Prospective Studies; D012015:Reference Standards; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic