March 2009 Swingle Metanalysis
Hanes M. Swingle, Tarah T. Colaizy, M. Bridget Zimmerman & Frank H. Morriss, Jr., Abortion and the Risk of Subsequent Preterm Birth: A Systematic Review with Meta-analyses, 54 J. REPRODUCTIVE MED. 95-108 (2009)
This metanalysis included 12 induced and 9 spontaneous abortion studies showed an adjusted odds ratio for preterm birth following one abortion of 1.25 (25% increase), and following 2 or more abortions the odds ratio was 1.64, (64% increase). A very important finding is that women with prior induced abortions have a 64% higher relative risk of a VERY preterm delivery (less than 32 weeks) than women with zero prior Induced abortions.
AAPLOG comment:
Preterm birth (PTB) (delivery at <37 weeks), and especially VERY preterm birth (<32 wks) contributes to infant mortality and childhood morbidity, including chronic lung disease, sensory deficits, cerebral palsy, cognitive impairments and behavioral problems. Among very preterm newborns, the risk of cerebral palsy increases fifty-five fold (5500 percent) over full-term newborns. E. Himpens, C. Van den Broeck, A. Oostra, P. Calders & P. Vanhaesebrouck, Prevalence, type, and distribution and severity of cerebral palsy in relation to gestational age: a meta-analytic review, 50 Developmental Med. Child Neurology 334-40 (2008).