The pregnancy loss iceberg: an overview of the outcome of spontaneous human conceptions. It is estimated that 70% of conceptions are lost prior to live birth. The majority of these losses occur prior to implantation or before the missed menstrual period, and since they are not revealed to the woman they are termed preclinical. In the pregnancy loss ‘iceberg’, they are therefore below the ‘waterline’. Figure reproduced with permission from Oxford University Press .