In this photograph taken Thursday, Nov. 21, 2013, Ken Ernst, left, and his wife Abigail Ernst, right, pose for The Associated Press with their 2-month-old daughter, Lucy, in their Oldwick, N.J. home. The couple conceived Lucy by using only one embryo through in vitro fertilization. With nearly half of all babies born using advanced fertility help being multiple births, doctors are now urging more couples to attempt pregnancy with just a single embryo. (AP Photo/Julio Cortez)BOSTON (AP) — In the 5 years because the "Octomom" case, giant more than one births have gone way down however the twin fee has barely budged. Now fertility experts are pushing a new intention: One.