Judge Clears Way for Arizona Abortion Ban to Start Law would block abortions beginning at 20 weeks By Mary Papenfuss, Newser User Posted Jul 31, 2012 1:06 AM CDT Updated Jul 31, 2012 1:21 AM CDT 90 comments Comments Arizona Gov. Jan Brewer was happy to sign the law. (AP Photo/The Arizona Republic, Nick Oza) (Newser) – Arizona's new law banning abortions beginning at what the state defines as 20 weeks of pregnancy is constitutional, a US district judge has ruled, setting the stage for the law to go into effect this week. The new law may force some pregnant women to opt for an abortion earlier, but the measure is constitutional because it doesn't ban abortions outright, determined Judge James Teilborg. He also said the state provided "substantial and well-documented" evidence that a fetus can feel pain by at least 20 weeks gestation, reports AP. The ban is set to go into effect for all women except in cases of medical emergencies on Thursday. The New York-based Center for Reproductive Rights has filed a notice that it plans to appeal the decision to the 9th US Circuit Court of Appeals, but it's not clear if that will hold up the law. The law will complicate "fetal defect" cases in which a number of babies with fatal problems must now be carried to term but will likely die in minutes or days after birth, reports the Arizona Republic. The new law forbids doctors from aborting most fetuses with a gestational age of 20 weeks or older, even in situations where the doctor discovers the fetus has such a defect. But the law defines gestational age as beginning with the first day of a woman's last period, which means most fetuses will typically have an actual gestational age of 18 weeks when abortions can no longer be performed. That's about the time ultrasound tests are conducted to detect abnormalities, notes the Republic.