Coasting, embryo development and outcomes of blastocyst transfer: a case-control study.

This study compared the effect on blastocyst development and clinical outcome of coasting in women at increased risk of moderate-severe ovarian hyperstimulation syndrome (OHSS; n=389) with a control group matched for age and basal FSH that did not undergo coasting (n=386) in IVF/intracytoplasmic sperm injection (ICSI) cycles. The main outcome measures were rate of blastocyst development and live birth. More cycles progressed to the blastocyst stage in the coasted group (n=169) compared with the control group (n=83; 43.4% versus 21.5%; P<0.001). The biochemical pregnancy, clinical pregnancy and live birth rates were similar (46.5% versus 42.0%; 40.6% versus 37.8%; 31.6% versus 30.1%). The duration of coasting up to 4 days did not affect progression to blastocyst stage. The multivariate model showed that coasting (OR 1.73, P=0.004) and the number of oocytes retrieved (OR 1.17, P=0.001) were positively correlated with blastocyst formation. Coasting, a measure to reduce the risk of OHSS, does not impair blastocyst development or clinical outcome. Coasting should remain an effective measure to prevent OHSS.