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Study finds 1 in 5 women are unlikely to know they're pregnant until after six weeks, due to common irregularities in periods

Young woman holding pregnancy test showing a positive result in bedroom, Wellness and healthy concept, Abortion problem, Selective focus.
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Young woman holding pregnancy test showing a positive result.

As we await the US Supreme Court's decision on two cases governing abortion, legal experts seem certain that any decision will have a major impact on reproductive rights. In states like Texas, a law making abortions illegal after six weeks of conception has effectively banned abortions for many women due to common irregularities in periods.

Many women are unaware of the pregnancy until their first missed period. A new study found that more than 1 in 5 women have periods so irregular they're unlikely to know they're pregnant until after six weeks. Jenna Nobles, director of UW-Madison's population research center, led the study into cycle irregularities.

"Our interest was motivated by the fact that menstrual cycles are highly irregular. Although we often consider periods to be 28 days with 14-day ovulation, that's actually relatively uncommon. What's really common is variability across people and across cycles within people," says Nobles.

The study also found some demographics of people are more likely to experience a variability in their cycles.

"We find that it's young people, people who are aged 18 to 25. People who identify as Hispanic and people who have a set of common medical conditions, like diabetes [and] polycystic ovarian syndrome," says Nobles.

It's these groups of people who may be unable to access a legal abortion because the window to learn about the pregnancy and make a decision is so short.

Nobles explains, "In the context of new abortion legislation, it became clear that laws that limit abortion to the period of time before fetal cardiac activity, this variability all of a sudden becomes really important. For most people, the first signal of a pregnancy is a missed period."

Although many people already experience barriers to abortion like regional accessibility, socioeconomic status, and transportation, this study is about the process that happens even before those barriers can be considered.

Nobles says that some lawmakers have a serious misunderstanding of what menstrual cycles and the first part of pregnancy look like in some cases. She's interested in also clarifying how short that window between missed periods and the initial electrical activity is.

"We're saying, look, there are disparate groups of people who desperately are unable to access abortion at all, apart from all of these other considerations," she explains. "The reason to highlight this is because these are features of individuals that are really entirely outside of their control."

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Joy is a WUWM host and producer for Lake Effect.
Kobe Brown was WUWM's fifth Eric Von fellow.
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