Outcomes of twin neonates and association with chorionicity and modes of conception

Abstract

Objective To investigate the pregnancy and neonatal outcomes in twin pregnancies and the association with chorionicity and modes of conception in order to provide evidence for early prevention and reduction of complications and life quality improvement of twin neonates. Methods This study retrospectively enrolled 756 women with twin pregnancies who gave birth at Peking University Third Hospital from January 1, 2014 to December 31, 2015. Clinical features of the mothers and newborns were collected, the pregnancy and neonatal outcomes were analyzed. Impacts of chorionicity and different modes of conception on the outcomes were also evaluated. Two independent-sample t test and Chi-square test were used as statistical methods. Results Twin pregnancies accounted for 6.7% (756/11 169) of all deliveries in the hospital during the study period and the preterm birth rate was 59.4% (449/756). Twenty five women underwent fetal reduction (3.3%, 25/756) and intrauterine death occurred in 85 pregnancies (11.2%, 85/756). Eventually 1 400 babies were born alive (92.6%, 1 400/1 512). Subgroup analysis suggested that compared with dichorionic diamniotic (DCDA) pregnancies, monochorionic diamniotic (MCDA) cases showed younger maternal age at conception [(30.5±4.2) vs (32.9±4.0) years, t=-7.412], smaller gestational age at delivery [(34.1±3.1) vs (35.7±2.2) weeks, t=-7.325] and higher preterm birth rate [78.4% (174/222) vs 51.5% (263/511), χ2=46.554], all P<0.05. Moreover, the incidence of neonatal complications, including respiratory distress syndrome [18.3% (40/219) vs 8.0% (21/261), χ2=11.210], neonatal pneumonia [18.3% (40/219) vs 8.8% (23/261), χ2=9.331] and sepsis [6.8% (15/219) vs 1.5% (4/261), χ2=8.854], etc. was higher in the MCDA group than those in the DCDA group, resulting in a higher mortality rate [7.8% (17/219) vs 1.1% (3/261), χ2=13.042] in the MCDA pregnancies, all P<0.05. Compared with spontaneously conceived twin pregnancies, women underwent in vitro fertilization-embryo transfer were older at conception [(33.4±3.8) vs (30.6±4.4) years, t=-6.095], delivered at a greater gestational age [(35.8±2.1) vs (35.2±2.6) weeks, t=-2.452] and had a lower preterm birth rate [49.2% (206/419) vs 63.5% (54/85), χ2=5.838] in the DCDA group, all P<0.05. No significant differences in the incidence of neonatal diseases were observed between the two subgroups. Conclusions The incidence of preterm birth is high in twin pregnancies. Compared with DCDA twin pregnancies, MCDA twin pregnancies are associated with more adverse outcomes due to higher incidence of neonatal diseases. In vitro fertilization-embryo transfer does not increase the incidence of preterm birth and the neonatal outcomes were comparable to those of spontaneously conceived ones. Key words: Pregnancy, twin; Pregnancy outcome; Premature birth; Infant, newborn, diseases; Incidence; Fertilization in vitro; Embryo transfer