In the second half of pregancy, we've traditionally learned that the gravid uterus compresses the inferior vena cava and therefore decreases cardiac output when patient is in a supine position. Therefore, we've learned that patients in the second half of pregnancy the patient should be placed in a left lateral tilt position.
However, it is difficult to perform good quality chest compressions when the patient is in a titled position.
Therefore, the optimal position for chest compressions on the patient in cardiac arrest in the second half of pregnancy is to have the patient in a supine position; and have another rescuer manually deflect the uterus to the patient's left side. This provides optimal compressions + optimal venous return.
References
Vanden Hoek TL, Morrison LJ, Shuster M, et al. Part 12: cardiac arrest in special situations. 2010 American Heart Association Guidelines for cardiopulmonary resuscitaiton and emergency cardiovascular care. Circulation 2010;122[suppl 3]:S829-S861.
