Featured Research

from universities, journals, and other organizations

Leading hypothesis for miscarriages, birth defects ruled out

Date:
July 3, 2014
Source:
Washington State University
Summary:
Reproductive biologists have ruled out the 'Production-Line Hypothesis,' one of the leading thoughts on why older women have an increased risk of miscarriages and children with birth defects.

Washington State University reproductive biologists have ruled out one of the leading thoughts on why older women have an increased risk of miscarriages and children with birth defects.

Related Articles


The 46-year-old "production-line hypothesis" says that the first eggs produced in a female's fetal stage tend to have better connections or "crossovers" between chromosomes. The hypothesis asserts that as a woman ages and ovulates eggs produced later, these eggs will have more faulty chromosomes -- leading to miscarriages and developmental abnormalities.

But after counting the actual chromosome crossovers in thousands of eggs, WSU researchers found those of eggs produced early in the fetal stage were no different from those produced later.

Abnormal cells early and late

"If the production-line hypothesis were true, you'd expect lots of abnormal cells and you would expect them all to be happening late," said Ross Rowsey, a doctoral candidate in WSU's Center for Reproductive Biology. "We do see a pretty high incidence of abnormal cells, but they're just as likely to be happening early as late."

Faulty chromosomes, in particular the incorrect number of chromosomes known as aneuploidy, account for more than one-third of human miscarriages and congenital birth defects, including Down syndrome. Their frequency rises dramatically in older women.

"The age of the woman is probably the most important risk factor associated with any human genetic disease," said Terry Hassold, a WSU professor of reproductive biology and co-author with Rowsey and others of a paper on their findings in the American Journal of Human Genetics.

"It's an extraordinary complication to human reproduction," he said. "By the time a woman is in her 40s, it's likely the majority of her eggs don't have the right number of chromosomes. And if you don't have the right number of chromosomes, you'll either have a miscarriage or a congenital disability."

Variations unrelated to age

The production-line hypothesis was put forth in 1968 by Alan Henderson and Robert Edwards, winner of the Nobel Prize for development of in-vitro fertilization. It has since become one of the most cited explanations for human aneuploidy.

To test the hypothesis, Rowsey looked at more than 8,000 eggs from 191 second-trimester fetal ovaries. The material came from elective abortions in accordance with the guidelines of the National Institutes of Health.

Rowsey treated eggs so proteins at chromosome crossovers would fluoresce, making dozens of glowing dots visible under a microscope. He then counted them and analyzed their distribution.

He saw a lot of variation within women and between women but no relationship to a woman's age.

"There have to be other factors involved," he said. "The abnormal crossovers can't be explaining all of it."

Resting proteins intriguing

Rowsey and Hassold said problems could be occurring at one, two or all of three stages: as the crossovers are formed, in the long rest stage before ovulation and/or as chromosomes divide during ovulation and fertilization.

Rowsey said he is particularly intrigued by the egg's rest stage, when its proteins are called upon to remain intact for what can be decades.

"I don't know a ton about protein stability," he said, "but it seems to me like a single protein sitting there for 40 years is highly unlikely. But studies from model organisms show that those proteins aren't replenished over time. I'm really interested to know what's going on in that time."


Story Source:

The above story is based on materials provided by Washington State University. The original article was written by Eric Sorensen. Note: Materials may be edited for content and length.


Journal Reference:

  1. Ross Rowsey, Jennifer Gruhn, KarlW. Broman, PatriciaA. Hunt, Terry Hassold. Examining Variation in Recombination Levels in the Human Female: A Test of the Production-Line Hypothesis. The American Journal of Human Genetics, 2014; 95 (1): 108 DOI: 10.1016/j.ajhg.2014.06.008

Cite This Page:

Washington State University. "Leading hypothesis for miscarriages, birth defects ruled out." ScienceDaily. ScienceDaily, 3 July 2014. <www.sciencedaily.com/releases/2014/07/140703125541.htm>.
Washington State University. (2014, July 3). Leading hypothesis for miscarriages, birth defects ruled out. ScienceDaily. Retrieved November 23, 2014 from www.sciencedaily.com/releases/2014/07/140703125541.htm
Washington State University. "Leading hypothesis for miscarriages, birth defects ruled out." ScienceDaily. www.sciencedaily.com/releases/2014/07/140703125541.htm (accessed November 23, 2014).

Share This


More From ScienceDaily



More Health & Medicine News

Sunday, November 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

WFP: Ebola Risks Heightened Among Women Throughout Africa

WFP: Ebola Risks Heightened Among Women Throughout Africa

AFP (Nov. 21, 2014) Having children has always been a frightening prospect in Sierra Leone, the world's most dangerous place to give birth, but Ebola has presented an alarming new threat for expectant mothers. Duration: 00:37 Video provided by AFP
Powered by NewsLook.com
Could Your Genes Be The Reason You're Single?

Could Your Genes Be The Reason You're Single?

Newsy (Nov. 21, 2014) Researchers in Beijing discovered a gene called 5-HTA1, and carriers are reportedly 20 percent more likely to be single. Video provided by Newsy
Powered by NewsLook.com
Raw: Paralyzed Marine Walks With Robotic Braces

Raw: Paralyzed Marine Walks With Robotic Braces

AP (Nov. 21, 2014) Marine Corps officials say a special operations officer left paralyzed by a sniper's bullet in Afghanistan walked using robotic leg braces in a ceremony to award him a Bronze Star. (Nov. 21) Video provided by AP
Powered by NewsLook.com
Milestone Birthdays Can Bring Existential Crisis, Study Says

Milestone Birthdays Can Bring Existential Crisis, Study Says

Newsy (Nov. 21, 2014) Researchers find that as people approach new decades in their lives they make bigger life decisions. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins