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Recording available 2/16-5/2
Recording available 2/16-5/2
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Poster Session 4

Category: Clinical Obstetrics

Poster Session 4

(1233) Birthweight discordancy and its direction: impact on cesarean risk during attempted vaginal twin delivery

Thursday, February 12, 2026
3:30 PM - 5:00 PM  

    Submitting Author and Presenting Author(s)

  • Roie Alter, MD (he/him/his)

    Hadassah Medical Center and Hebrew University of Jerusalem, Jerusalem, Israel
    Jerusalem, Yerushalayim, Israel

    • Coauthor(s)

  • IA

    Inbal Akavian, MD, MPH

    Hadassah Ein-karem hospital, Obstetrics and gynecology department, Jerusalem
    Jerusalem, Yerushalayim, Israel

  • SY

    Shlomo Yahalomy, MD

    Department of Obstetrics and Gynecology, Hadassah Hebrew University Medical Center, Ein Kerem
    Jerusalem, Yerushalayim, Israel

  • JR

    Joshua Isaac Rosenbloom, MD

    Hadassah Medical Center and Hebrew University of Jerusalem, Jerusalem, Israel
    Jerusalem, Yerushalayim, Israel

  • AT

    Aharon Tevet, MD

    Department of Obstetrics and Gynecology, Hadassah Hebrew University Medical Center, Ein Kerem
    Jerusalem, Yerushalayim, Israel

  • HR

    Hadar Rosen, MD

    Hadassah Ein-karem hospital, Obstetrics and gynecology department, Jerusalem
    Jerusalem, Yerushalayim, Israel

Objective:

To assess how birthweight discordancy influences the risk of urgent cesarean delivery during an attempted vaginal twin birth, and whether this risk varies based on discordancy direction, specifically, whether the larger twin is presenting (Twin A) or non-presenting (Twin B).

Study Design:

This retrospective cohort study included all diamniotic twin pregnancies at ≥32 weeks’ gestation with a cephalic-presenting first twin who underwent a trial of labor at a tertiary medical center between 1/2019-4/2025. Discordancy was defined as |Twin A – Twin B| ÷ larger twin birthweight >20%. Discordancy direction was categorized as "positive" (Twin B > Twin A) or "negative" (Twin A > Twin B). An SGA twin was defined as < 10th percentile by the Fetal Medicine Foundation birth weight charts. The Pearson correlation coefficient was employed to measure the linear correlation between discordancy and the mode of delivery. 

Results:

Of 1,017 women attempting vaginal twin delivery, 755(74.2%) achieved successful vaginal delivery of both twins, while 249 (24.5%) required cesarean delivery. Birthweight discordancy was associated with a significantly increased cesarean delivery rate compared to concordant twins (41.9% vs 23.7%, p< 0.001). When Twin A was larger, the cesarean delivery risk increased 87% (RR=1.87, 95% CI: 1.34-2.61, p< 0.001), whereas when Twin B was larger, risk was reduced by 39% though not statistically significant (RR=0.61, 95% CI: 0.35-1.07, p=0.085). Among discordant pairs, cesarean delivery was three times more likely when the presenting twin was larger (RR=3.07, 95% CI: 1.70-5.53, p< 0.001). Nearly all discordant cases involved at least one SGA infant.



Conclusion:

Birthweight discordancy increases the likelihood of urgent cesarean delivery in twin pregnancies undergoing a trial of labor. The increased risk may be influenced by the high rate of SGA fetuses in discordant pairs. This risk is notably higher when the presenting twin is the larger of the pair. Potential explanations include mechanical complications during labor or provider concern about the smaller second twin wellbeing during labor.