First-trimester inter- and intrafetal size discrepancies in bichorionic twins conceived by in vitro fertilization: can it predict pregnancy outcome?

In first-trimester bichorionic twin pregnancies conceived by in vitro fertilization, a discrepancy between the actual and estimated gestational age in the smaller fetus may be associated with adverse pregnancy outcomes.

Volume 108, Issue 2, Pages 296–301


Ron Bardin, M.D., Galia Oron, M.D., Yael Levy, M.D., Onit Sapir, Ph.D., Israel Meizner, M.D., Benjamin Fisch, M.D., Ph.D., Arnon Wiznitzer, M.D., Eran Hadar, M.D.



To evaluate the association between first-trimester inter- and intrafetal size discrepancies and pregnancy outcome, among bichorionic-biamniotic twins conceived by IVF.


A retrospective study design was used.


Tertiary university-affiliated medical center.


All women with a viable first-trimester bichorionic-biamniotic twin gestation, who conceived after IVF in 2007–2015.



Main Outcome Measure(s)

The association between fetal size differences and pregnancy outcome was analyzed. Intrafetal size discordance was defined as a difference between the actual gestational age calculated by ovum pickup (OPU) date and the evaluated gestational age by crown–rump length (CRL), for each twin. Intertwin size discrepancy was defined as a difference in CRL between the twins. The primary outcome was the number of live-born fetuses; the secondary outcome measures were gestational age at birth, birth weight percentile, and birth weight discordancy.


A total of 277 women met the study criteria and were divided into three groups by outcome: 218 (78.7%) live-born twins, 41 (14.8%) live-born singleton, and 19 (6.5%) non–live-born pregnancy. Among the smaller than expected twin, the association of CRL-OPU differences with the primary outcome was significant for twin live-born delivery (−1.43 day), singleton live-born delivery (−4.12 days), and non–live-born pregnancy (−6.72 days). For the relatively larger twin, the association was significant for non–live-born pregnancy (−4.33 days) compared with any live-born delivery, either singleton (−0.95 days) or twin (−0.21 days).


Among IVF conceived twin gestations, a CRL-OPU gap was associated with an increased risk of a negative pregnancy outcome.

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