title: Development of customized fetal growth charts in twins.
abstract: Twin gestations are at significantly higher risk of fetal growth restriction in comparison with singletons. Using fetal biometric charts customized for obstetrical and parental characteristics may facilitate an accurate assessment of fetal growth.
  
  
  
  The objective of the study was to construct reference charts for the gestation of fetal biometric parameters stratified by chorionicity and customized for obstetrical and parental characteristics.
  
  
  
  Fetal biometric measurements obtained from serial ultrasound examinations in uncomplicated twin pregnancies delivering after 36 weeks of gestation were collected by 19 Italian fetal medicine units under the auspices of the Società Italiana di Ecografia Ostetrica e Ginecologica. The measurements acquired in each fetus at each examination included biparietal diameter, head circumference, abdominal circumference, and femur length. Multilevel linear regression models were used to adjust for the serial ultrasonographic measurements obtained and the clustering of each fetus in twin pregnancy. The impact of maternal and paternal characteristics (height, weight, ethnicity), parity, fetal sex, and mode of conception was also considered. Models for each parameter were stratified by fetal chorionicity and compared with our previously constructed growth curves for singletons.
  
  
  
  The data set included 1781 twin pregnancies (dichorionic, n = 1289; monochorionic diamniotic, n = 492) with 8923 ultrasonographic examinations with a median of 5 (range, 2-8) observations per pregnancy in dichorionic and 6 in (range, 2-11) monochorionic pregnancies. Growth curves of twin pregnancies differed from those of singletons, and differences were more marked in monochorionic twins and during the third trimester. A significant influence of parental characteristics was found.
  
  
  
  Curves of fetal biometric measurements in twins are influenced by parental characteristics. There is a reduction in the growth rate during the third trimester. The reference limits for gestation constructed in this study may provide a useful tool for a more accurate assessment of fetal growth in twin pregnancies.
authors.affiliation: Department of Obstetrics and Gynecology, University of Parma, Italy.
authors.forename: Tullio
authors.initials: T
authors.lastname: Ghi
authors.affiliation: Department of Obstetrics and Gynecology, University of Brescia, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Prefumo
authors.affiliation: Department of Obstetrics and Gynecology, University of Brescia, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Fichera
authors.affiliation: Department of Obstetrics and Gynecology, University of Milan, Buzzi Children's Hospita, Italy.
authors.forename: Mariano
authors.initials: M
authors.lastname: Lanna
authors.affiliation: Department of Obstetrics and Gynecology, Presidio Ospedaliero Centro Piero Palagi, Firenze, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Periti
authors.affiliation: Department of Obstetrics and Gynecology, L. Mangiagalli, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Persico
authors.affiliation: Department of Obstetrics and Gynecology, Ospedale Sant'Anna, Turin, Italy.
authors.forename: Elsa
authors.initials: E
authors.lastname: Viora
authors.affiliation: Department of Obstetrics and Gynecology, University of Rome Tor Vergata, Rome, Italy. Electronic address: giuseppe.rizzo@uniroma2.it.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Rizzo
mesh_terms: D000005:Abdomen / Q000000981:diagnostic imaging / Q000254:growth & development; D000328:Adult; D001827:Body Height; D001835:Body Weight; D002508:Cephalometry; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000254:growth & development; D047109:Fetal Development; D057238:Growth Charts; D006801:Humans; D010290:Parents; D011247:Pregnancy; D059285:Pregnancy, Twin; D012189:Retrospective Studies; D012737:Sex Factors; D016216:Ultrasonography, Prenatal
keywords: fetal biometric parameters; fetal growth; fetal growth restriction; parental characteristics; twin pregnancies