Using Journal Citation Reports: Science Edition (2008) and the Social Sciences Citation Index database Brandt et al report the 100 most frequently cited journal articles in obstetrics and gynecology over the last 50 years.
We suggest that this type of analysis may well depend on the database that is selected. For example using Google Scholar we find:
Bump RC et al, The standardization of terminology of female pelvic organ prolapse and pelvic floor dysfunction. Am J Obstet Gynecol 1996;175:10-7 cited 1488 times.
Liggins GC and RN Howie, A controlled trial of antepartum glucocorticoid treatment for prevention of the respiratory distress syndrome in premature infants. Pediatrics 1972;50:515-25 cited 1210 times.
Olsen AL et al, Epidemiology of surgically managed pelvic organ prolapse and urinary incontinence. Obstet Gynecol 1997;89:501-6 cited 1143 times.
This is not a comprehensive list, but points out that such reports may do well by choosing a number of databases.