(CNN)Set politics aside for a minute. Ignore whatever laws are on the books. Hit snooze on any moral or religious alarm bells ringing in your head.
What you think or feel about Georgia becoming the latest US state to sign a bill that would ban abortions at six weeks -- or as soon as a fetal heartbeat can be detected -- is of no consequence for this story.
We've heard that women often don't know they're pregnant at six weeks, so we asked experts to tell us why. Here's what we learned.
Pregnancy isn't anticipated or confirmed
The reality is that nearly half of all pregnancies are unintended or, more specifically, 45-49% of the time they are unplanned, said Dr. Jen Villavicencio, an ob-gyn who lectures at University of Michigan Medicine and is also a fellow with the American College of Obstetricians and Gynecologists.
Those actively trying to get pregnant may be monitoring every aspect of their cycles and have pregnancy tests at the ready, but for many women getting pregnant comes as a surprise.
Even if a person is perfect at staying on top of birth control -- and most humans typically are not, said Villavicencio -- there's room for error. A birth control pill taken exactly as it is supposed to be taken, for example, fails 1-2% of the time, she said. This means one or two out of 100 users relying solely on the pill will get pregnant.
On a weekly basis, Villavicencio said she sees patients who are blindsided by the news. Maybe they're among the many who don't experience symptoms like morning sickness. Perhaps their menstrual cycle is irregular, more on that in a bit, or so routine that it doesn't garner much attention. Or maybe they experienced spotting, which is "extraordinarily common" after getting pregnant, and assumed that was just their period, she said.
They could have been conditioned, after trying for so long, to believe pregnancy wasn't possible for them. There's a chance they had someone -- even another doctor -- tell them they couldn't conceive. Villavicencio spoke about one patient with breast cancer who'd been told the chemo would shut down her ovaries -- except it didn't.
There are those who claim they knew instinctively when they got pregnant. But that's not the case most of the time, Villavicencio said.
If a woman suspects she's pregnant, she explained, at-home pregnancy tests vary in their ability to give accurate results, especially in the earliest stages. Generally, they work at five-to-six weeks, the doctor said. But even then, it can take multiple tests -- or a visit to a doctor -- to be 100% sure.
And an appointment with a doctor can often take another week or two to get.
Periods can be unpredictable
Irregular periods are not uncommon, especially in the early stages of experiencing menstruation or as a woman approaches menopause, Villavicencio said.
There are a multitude of other reasons, aside from age, that can make a menstrual cycle unreliable.
Villavicencio called out conditions like polycystic ovary syndrome, which causes cysts and hormonal imbalances and, as a result, leads to irregular menstruation in about 1-in-10 women, according to the US Department of Health and Human Services.
Medications, other illnesses and being an extreme athlete, too, can take a toll on a cycle, Villavicencio added.
The Office on Women's Health, at the Department of Health and Human Services, offers a long rundown of reasons a period may not arrive like clockwork.
Eating disorders, weight changes and obesity can lead to missed or irregular periods, So, too, can hyperthyroidism, stress or uncontrolled diabetes. Medicines, including those for anxiety or epilepsy, can mess up a cycle.
The list goes on.
Lack of education
In the United States, where sex education is far from uniform or available to everyone, there's plenty of room for gaps in understanding when it comes to pregnancy, said Jessica Sales, an associate professor at Emory University's Rollins School of Public Health, who often focuses on adolescent sexual and reproductive health.
Even though adults, too, have plenty to learn, education about sex and sexuality often falls on schools, said Sales, who co-authored a 2017 report "The State of Sex Education in the United States."
The required curriculum in schools, however, is "up to the discretion of states," said Sales. This means while some states require teaching that's "comprehensive, medically accurate and inclusive of gender and sex identities," other states may opt for a model focused on abstinence "with no legal requirement to go above and beyond that." This can leave individual school districts free to decide what they will, or won't, offer students.
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What's taught or not taught about reproductive biology and methods to prevent pregnancy have real-world consequences, Sales said.
"Young people have a lot of questions. They don't really comprehend how their bodies work, how menstruation and their cycles work," she said. "There's a lack of understanding of how a person would know they are pregnant."
This need for increased awareness, Sales said, transcends age and applies to us all.
