20. See . Shah and J. Zao, “ Induced termination of pregnancy and low birthweight and preterm birth: a systematic review and meta-analysis ,” BJOG 116(11): 1425-1442 (2009); . Swingle et. al., “ Abortion and the Risk of Subsequent Preterm Birth: A Systematic Review and Meta-Analysis ,” Journal of Reproductive Medicine 54:95-108 (2009); and Ankum WM, Lemmers M, Vershoor MAC, Hooker AB, Opmeer BC. Does dilation and curettage (D & C) increase the risk of preterm birth in subsequent pregnancies? A systematic review and meta-analysis .