Risk for one or two very low birth weight twins: A population study

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 ana 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). Conclusion: Nulliparas are at significantly increased risk of delivering one or two VLBW twins. (Obstet Gynecol 2000;96:400-2. (C) 2000 by The American College of Obstetricians and Gynecologists.).