PHOENIX (Reuters) – A federal judge refused on Monday to block an Arizona law banning most abortions after 20 weeks of pregnancy, clearing the way for the statute to take effect this week.

District Judge James Teilborg ruled that the measure, passed by the Republican-controlled state legislature and signed into law in April by Republican Governor Jan Brewer, is in keeping with standards that federal courts have set on limits to late-term abortions.

The new statute, due to take effect on Thursday, bars healthcare professionals from performing abortions after 20 weeks of pregnancy, except in the case of a medical emergency. Only a small number of such abortions are performed in the state each year.

Siding against abortion-rights advocates who had challenged the law, Teilborg said Arizona’s ban “does not impose a substantial obstacle” to abortions generally and that Arizona has the right to pass such legislation.

Two groups, the Center for Reproductive Rights and the American Civil Liberties Union, filed suit earlier this month on behalf of three Arizona abortion providers seeking to prevent the ban from being implemented.

The suit was believed to mark the first court test brought by physicians against similar abortion restrictions that have surfaced in a growing number of states since Republicans gained greater statehouse clout in the November 2010 elections, Center for Reproductive Rights officials said.

Six states have put laws into effect in the past two years banning most or all late-term abortions, based on hotly debated medical research suggesting that a fetus feels pain starting at 20 weeks of gestation. North Carolina enacted its own such ban decades ago.

Arizona and two other states – Georgia and Louisiana – have enacted similar bans that have not yet taken effect, center officials said.

The Supreme Court legalized abortion in 1973 but allowed states to place restrictions on the procedure from the time when a fetus could potentially survive outside the womb, except when a woman’s health was at risk.

(Editing by Steve Gorman and Will Dunham)