Texas law, known as Senate Bill 8, prohibits abortions once “cardiac activity” can be detected in an embryo. This activity consists of electrical pulses that can be picked up on ultrasound, but are not yet a true heartbeat, since heart valves form later in the embryonic development process.
Cardiac activity is detectable approximately six weeks after conception. Critics say this law amounts to an almost total ban on abortion partly because many women still don’t realize they are pregnant at the time. By the time women lose their periods, they are already around four weeks pregnant, and some women have irregular cycles or do not monitor their periods carefully enough to know the exact date their last periods started.
The law contains an exception, which allows abortions after heart activity is detected in medical emergencies. But it does not make exceptions for cases of rape or incest.
The practical effect of the law has been a sharp drop in legal abortions in Texas, although September figures do not show as steep a decline as many experts had predicted.