Studies comparing UFH and LMWH in medical patients, plus a large review of LMWH treatment during pregnancy. Tests of significance are by Fisher exact test (2-tailed). RCT indicates randomized controlled trial; DVT, deep-vein thrombosis; NA, not applicable; and NR, not reported. *Combined short- and long-term–treated LMWH groups. †Endpoint shown is symptomatic thrombosis associated with antibody formation (as per Table 2 in Lindhoff-Last et al³ ); for true HIT endpoint (defined as thrombocytopenia plus positive antibody), values are LMWH = 0/762 vs UFH = 1/375 (0.3%);P = .33. ‡Per Table 2 in Lindhoff-Last et al.³ Illustration by A. Y. Chen.