Difficult embryo transfers or blood on catheter and assisted reproductive outcomes: a systematic review and meta-analysis

We performed a systematic review and meta-analysis to examine whether a difficult embryo transfer or the presence of blood on the transfer catheter affects assisted reproduction outcomes. We searched the following databases: Cochrane Central Register of Controlled Trials (CENTRAL), Database of Abstracts of Reviews of Effects (DARE), MEDLINE, Embase, PsycINFO, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Literatura Latino-Americana e do Caribe em Ciências da Saúde (LILACS). We aimed to determine the risk ratio (RR) associated with difficult embryo transfer or the presence of blood on the transfer catheter for the following outcomes: live birth, clinical pregnancy, and miscarriage. We identified 3066 papers, of which 194 were reviewed and nine were included. The outcome of live birth was not reported in any of the included studies and the effect on miscarriage was too imprecise for any conclusions. Pooled analysis of five studies demonstrated lower clinical pregnancy rates following a non-easy embryo transfer (RR = 0.75; 95% CI = 0.66–0.86). This included three studies showing subjectively difficult transfers reducing clinical pregnancies (RR = 0.67; 95% CI = 0.51–0.87) and two studies in which the need for additional manoeuvers reduced clinical pregnancies (RR = 0.78; 95% CI = 0.67–0.91). The presence of blood on the transfer catheter did not affect clinical pregnancy rates (RR = 0.96; 95% CI = 0.82–1.14) in five studies. We concluded that low quality evidence suggests that a difficult embryo transfer but not a bloody catheter reduces the chance of achieving a clinical pregnancy. More good quality studies are needed to evaluate the effect of difficult embryo transfer and the presence of blood on the catheter on the main outcomes of assisted reproduction.