AUSTIN (KXAN) — Texas and its controversial restrictive abortion law was top of mind on Saturday — as over 600 marches and rallies took place ahead of Supreme Court arguments Monday.

Protesters and state officials met at the Texas Capitol Saturday morning to denounce the passage of Senate Bill 8, which bans abortion once cardiac activity is detected, which is usually around six weeks into a pregnancy and before many people even realize they’re pregnant. The event was hosted by activist group Women’s March.

The polarizing GOP-led SB 8 snagged global headlines after going into effect Sept. 1, becoming the most restrictive abortion law in the U.S. While it’s faced praise from conservatives, opponents say it’s a full-on abortion ban disguised as a limitation. Moreover, many (including President Joe Biden) say it’s in direct violation of Roe v. Wade — and may even be the unraveling of the Supreme Court’s abortion-legalizing 1973 decision.

At least 35 Texas cities were expected to host marches, including Houston, San Antonio, El Paso, McAllen and Abilene.

Events were held in 49 other states, including in New York City, Los Angeles, Washington, D.C. and Chicago. One event will also be held overseas in Madrid, Spain.

Among its most condemned aspects, SB 8 also allows private citizens to sue abortion providers or anyone who helps someone get an abortion. Critics say this would put a bounty on people’s heads and encourage frivolous lawsuits. Citizens can be sued for $10,000 or more if an abortion is performed outside of the six-week period.

Notably, SB 8 does not include exceptions for victims of rape or incest. In response to detractors, Gov. Greg Abbott said the law gives rape victims the six-week period to get an abortion and thus “does not do that [force victims to have their assaulter’s child].” Instead, Abbott said Texas would “eliminate” rapists. The comments were widely ridiculed and debated, as many argue there’s not a realistic way to do this.

In September, U.S. Attorney General Merrick Garland promised the U.S. Department of Justice would protect those seeking abortions while it urgently works to protect access to abortion. The bill made it to the U.S. Supreme Court, who ultimately allowed the law to stand. On Monday, SCOTUS will take another look, though opponents worry the now-majority conservative court could set a Roe v. Wade overturn in motion.

Abbott also later banned the use of medication abortion after seven weeks, including a ban on sending prescription pills through the mail.

The so-called “Heartbeat Bill,” has also faced criticism as there’s speculation in the medical community whether activity often considered a heartbeat even is a heartbeat. Some medical experts argue there’s no fully developed heart at the six-week gestational period and that the sound referred to as a heartbeat is actually “electrically induced flickering” of fetal tissue, called a “pole.”

Ob-gyn Dr. Jen Gunter says that the “pole” is thickening at the end of the yolk sac — the circular blob seen on ultrasounds — is merely cardiac activity of cells but not an independent heart with a heartbeat. Gunter writes that while calling the “fetus” a “fetus” at this stage of pregnancy is technically correct, it’s merely “a 4 mm thickening next to a yolk sac.”