That timeline means that abortion bans at six weeks, enacted in Texas, Oklahoma and Idaho, take effect earlier in pregnancy than many people think, Verma says. As nonsensical as that sounds, it’s the simplest way medical professionals can date a pregnancy. (Day 1 is the first day of menstruation day 1 is also when a pregnancy officially begins in the month an egg is fertilized.) That means that when a sperm fertilizes an egg, a person is already officially two weeks pregnant. An ovary releases an egg around day 14 of an average 28-day menstrual cycle ( SN: 6/19/21). The standard pregnancy clock actually starts ticking before a sperm cell encounters an egg, two weeks before, on average. That’s because how dates are determined is supremely confusing. The early timeline of a pregnancy is easy to misunderstand. Here’s what’s known about five key aspects of pregnancy biology that often come up in abortion debates. “There aren’t these set black-and-white points for much of this,” says obstetrician-gynecologist Nisha Verma, a fellow with the American College of Obstetricians and Gynecologists in Washington, D.C.

Despite the rhetoric around these issues, clear lines - between having a heart and not having a heart or being able to survive outside of the uterus - are scarce, or nonexistent.

Like most aspects of biology, early human development involves many complex processes.

When does fetal heartbeat start