That’s because those chambers haven’t yet developed. “Heartbeat laws” are not what they seem.Ī Texas law bans abortions “after detection of an unborn child’s heartbeat.” But the rhythmic sounds heard on an ultrasound early in pregnancy aren’t caused by the opening and closing of heart valves as they move blood through the heart’s chambers, the motion that produces a typical lub dub sound. “In fact, if they aren’t treated and continue to grow, they will kill the patient.” Laws that apply to a fertilized egg could “limit our ability to treat patients for ectopic pregnancies,” she says. “These are pregnancies that under no circumstance can become a healthy pregnancy,” Sandoval says. Called an ectopic pregnancy, this can lead to life-threatening medical emergencies when the growing tissue ruptures the tube and internal bleeding ensues. That includes fertilized eggs that lodge in the wrong spot, the fallopian tube, for example. Lawmakers in some states are considering abortion rules that apply to a fertilized egg Oklahoma had already passed such a law. “There are so many things other than the sperm meeting the egg that actually matter for this to become a pregnancy that has a chance to develop further,” says Selina Sandoval, an obstetrician and gynecologist who specializes in complex family planning at the University of California, San Diego. And the right balance of hormones need to be churned out to support the pregnancy. The growing ball of cells needs to travel to the uterus and implant itself in the right spot. ![]() The genetic material needs to combine in the right way. “Equating them doesn’t make sense from a medical standpoint.” Up to 50 percent of fertilized eggs do not implant in the uterus, researchers have estimated. But a fertilized egg does not automatically lead to a pregnancy, says obstetrician and gynecologist Jonas Swartz of Duke University School of Medicine. That meeting, which usually takes place in one of the two fallopian tubes near the ovaries, is fertilization, a process in which two cells fuse and mingle their genetic contents, creating what’s known as a zygote ( SN: 1/10/15). Pregnancy takes more than sperm meeting egg. Birth control isn’t 100 percent effective, and certain types can eliminate menstruation altogether, throwing even more uncertainty into the early timeline of pregnancy. Many women have irregular menstrual cycles. What’s more, these dates are based on averages. Such bans leave a person very little time - two weeks after a missed period - to access an abortion. Counting back, that’s two weeks after a missed period, which is often a person’s first indication that they might be pregnant. The ban would start four weeks after fertilization. “Some people think it’s from the date of conception.” Neither is correct. “Some people will say the six weeks is after your first missed period,” she says. In 2020, she surveyed people in Georgia, where she was practicing medicine at the time, about their understanding of the timing. 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.
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