A comparison of spontaneously conceived twins and twins conceived by artificial reproductive technologies.

Evidence on pregnancy outcomes of twins conceived by artificial reproductive technology (ART) compared with those naturally conceived (NC) is conflicting. We retrospectively audited outcomes of ART and NC twin births at Royal Maternity Hospital, Belfast from 01.01.2002-31.12.2003. Of 202 twins, 53 (26%) were ART and 149 (74%) were NC. ART group had increased maternal age (p < 0.001), more primiparous mothers (p < 0.001), used more peri-conceptual folic acid (p = 0.01), booked earlier for antenatal care (p < 0.05), delivered by caesarean section (p = 0.035) more often at a later gestation (p = 0.048) with a higher birth weight (p < 0.05). The NC group had increased congenital anomalies (p = 0.005) and babies requiring neonatal intensive care (p = 0.003). Of confirmed cases, ART twins were all dichorionic compared with 81.7% of NC (p = 0.002). Most neonatal outcome differences disappeared when NC dichorionic twins were compared with ART twins. ART twins have fewer complications than NC twins. Chorionicity accounts for most of these differences.