"The various sections specifying prohibitions on abortions at various weeks prior to viability cannot be allowed to go into effect on August 28, as scheduled," US District Judge Howard Sachs wrote on Tuesday in an 11-page opinion, CNN reported.
"However formulated, the legislation on its face conflicts with the Supreme Court ruling that neither legislative or judicial limits on abortion can be measured by specified weeks or development of a fetus; instead, 'viability' is the sole test for a State's authority to prohibit abortions where there is no maternal health issue," Sachs wrote.
Tuesday's ruling comes after two other federal judges blocked similar abortion restrictions in Arkansas and Ohio earlier this summer, as a slew of state laws looking to challenge Roe vs. Wade, the 1973 landmark ruling legalising abortion nationwide, make their way through the courts.
The Missouri law in question would penalise medical professionals who perform abortions after eight weeks into a pregnancy before many women know that they are pregnant, and well before the 24-week viability standard established by Roe with up to 15 years in prison.
The law does not include exceptions for instances of rape or incest, only for instances of "medical emergency," such to prevent a pregnant woman's death or "substantial and irreversible physical impairment."
Alexis McGill Johnson, acting president and CEO of Planned Parenthood, praised the ruling and vowed to continue to fight the law in court.
"Today's decision blocks a harmful law that bans abortion before many know they're pregnant," she wrote in a statement. "What little abortion access in Missouri is left, will stay in place for the time being."
"Let's be very clear: these severe restrictions on abortion access do nothing to address disability rights or discrimination," Johnson added. "They only stigmatise abortion and shame the people who seek that care."
Planned Parenthood, the American Civil Liberties Union and Paul, Weiss the law firm that argued in support of legalizing same-sex marriage in a landmark Supreme Court case filed the case last month.
The law would ban abortion outright should the Supreme Court overturn Roe. It also includes bans on abortion at 14, 18 and 20 weeks, which could go into effect if a court finds the eight-week ban invalid.
( With inputs from IANS )