Mississippi residents have rejected a proposed constitutional amendment to define a fertilized human egg as a person. The measure would have conferred rights on an embryo from the moment of conception, effectively outlawing abortion, even in rape or incest cases. More than 55% voters rejected the so-called personhood initiative. Mississippi already has tough abortion regulations and only one clinic which performs the procedure. Correspondents say that even if the amendment had passed then it would have likely faced legal challenges, as it contradicts the right to abortion established by the Roe v Wade Supreme Court ruling of 1973. Strong support\' Voters on Tuesday were asked: \"Should the term \'person\' be defined to include every human being from the moment of fertilization, cloning, or the functional equivalent thereof?\" Backers of the amendment to the state\'s constitution collected more than 100,000 signatures from registered voters to introduce it to the ballot. Pro-choice campaigners outside Capitol Hill in Washington DC on 7 April 2011 Critics warn of major legal repercussions if an embryo is granted equal rights to its mother \"Personhood is the key to all human rights,\" said Keith Mason, president of Personhood USA. \"We believe that by legally changing the definition of what a person is, it can undermine Roe v Wade and outlaw abortion.\" Tuesday\'s vote could have also led to the banning of some birth control methods in Mississippi. The amendment has attracted strong support in the conservative and religious state. A poll taken before the vote found that 45% of voters in Mississippi backed the measure, 44% were against, and 11% undecided. The state\'s Democratic and Republican candidates for governor, who are also running for election on Tuesday, have both come out in favour of the amendment. But opponents say that there could be wide-ranging legal repercussions if an embryo has equal rights to its mother. Dr Randall Hines, a Mississippi infertility specialist, said: \"This amendment represents the greatest moment of government interference in the delivery of health care that we\'ve ever seen.\" The initiative will probably pass but will not survive anticipated legal challenges, according to one commentator. Marty Wiseman, director of the John C Stennis Institute of Government at Mississippi State University, told Reuters news agency: \"Mississippi can\'t negate Roe v Wade, which this would do.\" \"Who knows the twists and turns it is going to take before it is shot down by the Supreme Court,\" he added. Personhood campaigners are also hoping to put the question to voters in the US states of Ohio, Florida, and South Dakota in 2012. But similar measures have been rejected twice by wide margins by voters in Colorado in 2008 and 2010.