title: Risk for one or two very low birth weight twins: a population study.
abstract: OBJECTIVE
  To calculate the frequencies of very low birth weight (VLBW) neonates among twins in a large population database.
  
  
  METHODS
  The database comprised 12,567 live-born twin pairs delivered from 1993 to 1998 in Israel. Low birth weight (LBW) and VLBW were defined as less than 2500 and 1500 g, respectively. We counted the number of pairs with VLBW neonates in three combinations: VLBW-VLBW, VLBW-LBW, and VLBW-over 2500 g. We compared the subsets of nulliparas and multiparas and the frequency of like- versus unlike-sex twins.
  
  
  RESULTS
  The frequency of at least one VLBW twin was significantly higher among nulliparas than multiparas (odds ratio [OR] 2.3; 95% confidence interval [CI] 2.1, 2.6; P <.001). For pairs with VLBW-VLBW and VLBW-LBW combinations, a significantly higher frequency was found among nulliparas than multiparas (OR 2.0; 95% CI 1.7, 2.8; P <.001 and OR 2.6; 95% CI 2.2, 3.1; P <.001, respectively). The risk seemed to be accentuated in like-sex twins. Overall, the risk of having at least one VLBW infant was 1:5 among nulliparas and 1:12 among multiparas. The risk of having two VLBW twins among nulliparas (1:11) was double that of multiparas (1:22).
  
  
  CONCLUSIONS
  Nulliparas are at significantly increased risk of delivering one or two VLBW twins.
authors.affiliation: Department of Obstetrics and Gynecology, Kaplan Medical Center, (affiliated with the Hadassah-Hebrew University School of Medicine, Jerusalem), Rehovot, Israel. blick@netvision.net.il
authors.forename: I
authors.initials: I
authors.lastname: Blickstein
authors.forename: R D
authors.initials: RD
authors.lastname: Goldman
authors.forename: R
authors.initials: R
authors.lastname: Mazkereth
mesh_terms: D003430:Cross-Sectional Studies; D005260:Female; D005317:Fetal Growth Retardation / Q000453:epidemiology*; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D019102:Infant, Very Low Birth Weight; D007557:Israel; D008297:Male; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000706:statistics & numerical data*; D012306:Risk; D012737:Sex Factors