STUDY QUESTION: Is there an association between discordance in embryonic growth and fetal loss at the time of the 11-14-week scan in twin pregnancies? SUMMARY ANSWER: Regardless of the chorionicity, crown rump length (CRL) discordance at 7(+0)-9(+6) weeks is predictive of subsequent single fetal demise in the first trimester. WHAT IS KNOWN ALREADY: Previous small studies have reported a variable association between discordance in embryonic growth and subsequent fetal loss. STUDY DESIGN, SIZE, DURATION: Retrospective study of all twin pregnancies of known chorionicity from a large regional cohort over a 10-year period. A total of 1356 twin pregnancies (288 monochorionic and 1068 dichorionic) were included in the study. PARTICIPANTS, SETTING, METHODS: Women presenting to the early pregnancy unit were included in the study. Logistic regression, ROC curve and Kaplan-Meier analyses were performed to evaluate the association between CRL discordance at 7(+0)-9(+6) weeks and spontaneous single fetal loss diagnosed at the 11-14-week scan. A systematic review was also performed using MEDLINE, EMBASE, Cinahl and the Cochrane Library in order to explore the relationship between early growth discordance and single fetal loss in twin pregnancies. MAIN RESULTS AND THE ROLE OF CHANCE: There were 111 (8.2%) single fetal losses diagnosed at 11-14 weeks in this cohort. At multivariate analysis, CRL discordance percentile [odds ratio (OR) 1.20; 95% confidence interval (CI), 1.12-1.63, P < 0.0001] and CRL <5th centile of at least one twin (OR, 2.21; 95% CI 1.23-4.24, P = 0.023), but not chorionicity (P = 0.486) or maternal age (P = 0.283) was independently associated with the loss of one fetus at the 11-14-week scan. The predictive accuracy of CRL discordance for single fetal loss was high (AUC = 0.93; 95% CI = 0.91-0.94). A significant association was found between the increase in the degree of embryonic discordance and the likelihood of early fetal loss (P < 0.0001). LIMITATIONS, REASONS FOR CAUTION: Only a high-risk population was analysed. Therefore, the patients studied were not a representative sample from the population of women pregnant with twins. WIDER IMPLICATION OF THE FINDINGS: Twin pregnancies, in particular those resulting from assisted conception, are scanned frequently, particularly during the early stages of pregnancy. The findings of this study are likely to prove important in counselling parents about the short-term outcome of the pregnancy when an embryonic discordance is present. STUDY FUNDING/COMPETING INTEREST(S): No external funding was sought for this study. None of the authors has any conflicts of interest to declare.
STUDY QUESTION: Is there an association between discordance in embryonic growth and fetal loss at the time of the 11-14-week scan in twin pregnancies? SUMMARY ANSWER: Regardless of the chorionicity, crown rump length (CRL) discordance at 7(+0)-9(+6) weeks is predictive of subsequent single fetal demise in the first trimester. WHAT IS KNOWN ALREADY: Previous small studies have reported a variable association between discordance in embryonic growth and subsequent fetal loss. STUDY DESIGN, SIZE, DURATION: Retrospective study of all twin pregnancies of known chorionicity from a large regional cohort over a 10-year period. A total of 1356 twin pregnancies (288 monochorionic and 1068 dichorionic) were included in the study. PARTICIPANTS, SETTING, METHODS:Women presenting to the early pregnancy unit were included in the study. Logistic regression, ROC curve and Kaplan-Meier analyses were performed to evaluate the association between CRL discordance at 7(+0)-9(+6) weeks and spontaneous single fetal loss diagnosed at the 11-14-week scan. A systematic review was also performed using MEDLINE, EMBASE, Cinahl and the Cochrane Library in order to explore the relationship between early growth discordance and single fetal loss in twin pregnancies. MAIN RESULTS AND THE ROLE OF CHANCE: There were 111 (8.2%) single fetal losses diagnosed at 11-14 weeks in this cohort. At multivariate analysis, CRL discordance percentile [odds ratio (OR) 1.20; 95% confidence interval (CI), 1.12-1.63, P < 0.0001] and CRL <5th centile of at least one twin (OR, 2.21; 95% CI 1.23-4.24, P = 0.023), but not chorionicity (P = 0.486) or maternal age (P = 0.283) was independently associated with the loss of one fetus at the 11-14-week scan. The predictive accuracy of CRL discordance for single fetal loss was high (AUC = 0.93; 95% CI = 0.91-0.94). A significant association was found between the increase in the degree of embryonic discordance and the likelihood of early fetal loss (P < 0.0001). LIMITATIONS, REASONS FOR CAUTION: Only a high-risk population was analysed. Therefore, the patients studied were not a representative sample from the population of women pregnant with twins. WIDER IMPLICATION OF THE FINDINGS: Twin pregnancies, in particular those resulting from assisted conception, are scanned frequently, particularly during the early stages of pregnancy. The findings of this study are likely to prove important in counselling parents about the short-term outcome of the pregnancy when an embryonic discordance is present. STUDY FUNDING/COMPETING INTEREST(S): No external funding was sought for this study. None of the authors has any conflicts of interest to declare.