Abortion after week six is now allowed only if the woman's life is in danger.
The new law was signed by Texas Gov. Greg Abbott in May.
Despite diligent attempts by abortion rights activists to stop the law, it came into force on Wednesday.
- Our Creator blessed us with the gift of life.
Despite this, millions of children lose the right to their lives every year due to abortion.
In Texas, we work to protect those lives, the governor said when he signed the law.
According to abortion law groups, 85-90 percent of all abortions in Texas are performed after week six, which means that many clinics may be forced to close.
Private individuals can report
The new law also means that anyone can report and sue people who are suspected of having helped a woman perform an abortion after the new time limit.
Opponents of abortion claim that what they call "fetal heartbeat" can be heard in week six.
However, the term has been condemned as severely misleading by medical authorities as a human embryo in that week is as large as a grain of rice.
Despite the law's entry into force, a court can still suspend the ban, according to legal experts.
Contrary to the Constitution
The new law in Texas is clearly in violation of the Constitution - the US Constitution, according to President Biden, who promises to defend the right to abortion.
"Texas law will significantly impair women's access to the health care they need, especially in communities with blacks and low-income earners," Biden said in a statement on Wednesday.
"My administration is deeply committed to the constitutional right established in the Roe v. Wade case five decades ago and will protect and defend it," he added.
In the case of Roe v. Wade, the Supreme Court of the United States ruled in 1973 that free abortion is part of the constitutionally protected right to privacy.
Biden also sees it as outrageous that private individuals can report and sue people who they believe have helped to carry out abortions.