Pregnancy-related venous thrombosis: comparison between spontaneous and ART conception in an Italian cohort

OBJECTIVE: To evaluate in an Italian cohort the incidence of venous thromboembolic events (VTE) in pregnancies after assisted reproductive technologies (ART). SETTING: Thrombosis and Haemostasis Unit at I.R.C.C.S. ‘Casa Sollievo della Sofferenza’, S. Giovanni Rotondo. PARTICIPANTS: A prospective cohort of 998 women advised to undergo ART was referred by local fertility clinics from April 2002 to July 2011. Follow-up information was obtained during the check-up and/or by phone interviews. In a cohort of women who consecutively gave birth (n=3339) after spontaneous conception in our Institution, information on the diagnoses of pregnancy-related venous thromboses was obtained by linkage to a patient administrative register. PRIMARY AND SECONDARY OUTCOME MEASURES: We calculated the incidence of VTE and superficial venous thrombosis in successful ART cycles and compared it with that of the general population conceiving spontaneously. RESULTS: Overall, 684 ART cycles were carried out by 234 women, who achieved a clinical pregnancy; in case of more than one successful cycle, only the first pregnancy was considered. Three vein thromboses (two VTE and one superficial vein thrombosis) were recorded. An antithrombotic prophylaxis with LMWH alone or combined with low-dose aspirin was prescribed in 23/234 (9.8%) women. In the reference cohort of 3339 women, a total of 11 vein thromboses were observed: six VTE and five SVT. The two-tailed Fisher exact test showed a trend towards statistical significance (p: 0.06, OR: 3.9, 95% CI 0.87 to 15.3). After the exclusion of superficial thromboses in both the groups, we found that the incidence of VTE in our population of women who had undergone ART was 2/234 pregnancies (8.5 ‰), whereas that in our reference population was 6/3339 (1.8 ‰) (p: 0.09). CONCLUSIONS: Our data show a slightly higher incidence of vein thromboses in pregnancies after ART than in those after natural conception.