Twin discordance: dogma or disease?

OBJECTIVE: We sought to investigate the research question: What is the impact of twin discordance on perinatal outcome? METHODS: 982 consecutive twin pregnancies (1964 infants) were evaluated for ohstetrical and neonatal characteristics. Discordance was denned as birth weight difference >20%. Birth weight discordancy categories were further stratified into 5 categories: Low-9 (n = 532); 10-20 (n = 313); 21-25 (n = 55); 26-30 (n = 32); 31-high (n = 50). RESULTS: Maternal characteristics such as age (24 ±6 yrs), parity, and gestational age at deliver)' (36 ±4 wks) were comparable between [he groups. Complications such as preeclampsia were similar for the discordant and non-discordant groups (24% vs. 17%, respectively), clinical polyhydramnios (2.9% vs. 1.7%, respectively), c-section (34% vs. 44% ns, respectively). When the discordant (>20%) and nondiscordant (<20%) groups were compared, a significantly higher rate of stillbirth was found in the discordant group (odds ratio 5.6; 95% confidence interval 2.3-11.7); fetal distress in labor (OR 2.08; 95% CI 1.2-3.8); Apgar score at 5 min. <7 (OR 2.3; 95% CI 1.4-4.1 ). No significant difference was found in the rates of anomalies, neonatal death and pulmonary complications (RDS, hyalin membrane disease, and respiratory support). Patients were further stratified to evaluate the association between neonatal outcome and larger degrees of discordancy: Discordancy Rates (%) Low- 9 10-20 27-25 26-30 31 -high Stillbirths 1.3% 2.5% 5.5% 3.1%, 10% Neonatal Death 3.5% 3.8% 1.8% 0 0 Fetal Distress 8.4% 9.4% 14.6% 15.4% 17.9% Apgar 5min <7 6.2% 7.3% 9.1% 9.4% 18.0% Anomalies 5.6% 6.6% 9.8% 11.5% 10.7% Lung Comp. 14.5% 11.8% 14.6% 11.5% 17.9% Complications (Apgar, metabolic, birth defects, fetal distress, stillbirth rate) were two-fold higher in the discordant group (OR 1.74; 95% CI, 1.2-2.7). CONCLUSION: Our data suggests that birth weight discordancy is a clinical entity with an increased impact on neonatal morbidity and fetal mortality. The larger the discordancy, the greater the negative impact on outcome.