 According to the Nielsen ratings system , " Rosemary 's Baby " was viewed by an average of 6 @.@ 5 million American viewers . The episode achieved a 3 @.@ 1 / 8 in key 18 – 49 demographic . The 3 @.@ 1 rating refers to 3 @.@ 1 % of all 18- to 49 @-@ year @-@ olds in the U.S. , and the 8 share refers to 8 % of all 18- to 49 @-@ year @-@ olds watching television at the time of the broadcast . In the U.S. , " Rosemary 's Baby " was up by 19 % in the rating demographic compared to the previous episode , " The Collection , " receiving its highest result since the second season premiere episode , " SeinfeldVision , " on October 4 , 2007 . 
 According to the Nielsen ratings system , " Rosemary <a href='null_genetive' title='1'><mark>'s</mark></a>Baby " was viewed by an average of 6 @.@ 5 million American viewers . The episode achieved a 3 @.@ 1 / 8 in key 18 – 49 demographic . The 3 @.@ 1 rating <a href='uninflect' title='2'><mark>refers</mark></a> to 3 @.@ 1 % of all 18- to 49 @-@ year @-@ olds in the U.S. , and the 8 share <a href='uninflect' title='3'><mark>refers</mark></a> to 8 % of all 18- to 49 @-@ year @-@ olds watching television at the time of the broadcast . In the U.S. , " Rosemary <a href='null_genetive' title='4'><mark>'s</mark></a>Baby "<a href='been_done' title='5'><mark></mark></a> was up by 19 % in the rating demographic compared to the previous episode , " The Collection , " receiving its highest result since the second season premiere episode , " SeinfeldVision , " on October 4 , 2007 . 
According to the Nielsen ratings system , " Rosemary  Baby " was viewed by an average of 6 @.@ 5 million American viewers . da episode achieved a 3 @.@ 1 / 8 in key 18 – 49 demographic . Tda3 @.@ 1 rating refer to 3 @.@ 1 % of alll 18- to 49 @-@ year @-@ olds in thda.S. , and the 8 share refer to 8 % of all 18- to 49 @-@ year @-@ olds watchin television at the time of thedaoadcast . In the da. , " Rosemary  Baby " done was up by 19 % in the rating demographic compared to the pdaious episode , " The Collection , " receiving its highest result since the sedad season premiere episode , " SeinfeldVision , " on October 4 , 2007 .