MULTIFETAL PREGNANCY REDUCTION IS NOT ASSOCIATED WITH AN INCREASED RISK OF INTRAUTERINE GROWTH RESTRICTION, EXCEPT FOR VERY-HIGH-ORDER MULTIPLES

OBJECTIVE: Our purpose was to investigate whether multifetal pregnanci es reduced to twins have an increased risk of intrauterine growth rest riction and discordant birth weight. STUDY DESIGN: This retrospective cohort study investigated the rates of birth weight discordance >20% a nd intrauterine growth restriction using both twin and singleton birth weight curves in 441 twin deliveries after multifetal pregnancy reduc tion (233 reduced from triplets, 156 from quadruplets, and 52 from qui ntuplets or greater) compared with 136 nonreduced dichorionic twins. R ESULTS: No significant difference was found in the frequency of birth weight discordance and in the overall incidence of intrauterine growth restriction by both twin and singleton birth weight curves when pregn ancies that underwent multifetal pregnancy reduction were compared wit h the control group. There was, however, an almost twofold increase in the rate of intrauterine growth restriction in pregnancies with a sta rting fetal number of 5 or more (23.1%) compared with that in those re duced from triplets or quadruplets (12.1%) when the twin curve standar d was used (P=.03). This difference disappeared when these groups were compared with a singleton nomogram. CONCLUSION: This study suggests t hat multifetal pregnancy reduction is not associated with an increased risk of intrauterine growth restriction unless the starting fetal num ber is greater than or equal to 5. This finding provides a further rat ionale to avoid transferring excessive numbers of preembryos after in vitro fertilization.