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Pregnancy Timeline by SemestersFetal liver is producing blood cellsHead may position into pelvisBrain convolutions beginFull TermWhite fat begins to be madeWhite fat begins to be madeHead may position into pelvisImmune system beginningImmune system beginningPeriod of rapid brain growthBrain convolutions beginLungs begin to produce surfactantSensory brain waves begin to activateSensory brain waves begin to activateInner Ear Bones HardenBone marrow starts making blood cellsBone marrow starts making blood cellsBrown fat surrounds lymphatic systemFetal sexual organs visibleFinger and toe prints appearFinger and toe prints appearHeartbeat can be detectedHeartbeat can be detectedBasic Brain Structure in PlaceThe Appearance of SomitesFirst Detectable Brain WavesA Four Chambered HeartBeginning Cerebral HemispheresFemale Reproductive SystemEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterSecond TrimesterFirst TrimesterFertilizationDevelopmental Timeline
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Home | Pregnancy Timeline | News Alerts | News Archive July 9, 2013


Female rats whose mothers had been exposed to stress and who themselves underwent
a "stressful" behavioral test showed higher levels of CRF-1 than other groups.

WHO Child Growth Charts




Stress before conception causes gene changes in baby

Exposure to distress, even before she conceives, creates a chain reaction beginning in the gene (linked to a stress mechanism) — in the ovum she carries — and later in the brains of her offspring.

In previous studies conducted in professor Micah Leshem's lab, it was found that exposing rats to stress before they had even conceived (even as early as their "teen" age) influenced the behavior of their offspring. This recent study conducted in the lab of Dr. Inna Gaisler-Salomon by PhD student Hiba Zaidan, in cooperation with professor Leshem, sought to examine whether there was an influence on gene expression.

"There are many systemic similarites between humans and rats — which questions the transgenerational influence of stress we see in rats — does the same effect happen in humans as well." researchers observed. "Previously, we only saw evidence in behavior, now we've found effects at the genetic level."

In the study recently published in the journal Biological Psychiatry, the researchers focused on the gene known as CRF-1, a gene linked to the body's stress-control system and expressed in the brain.

The researchers looked at female rats 45 days old, a time in rats that is parallel to human adolescence. Some of the rats were exposed to "minor" stress, including changes in habitat temperature and changes in daily routine, for seven days. These animals were compared to a control group that was not exposed to any stress at all. The two sets of rats were then mated.

In the first part of the study, researchers examined the eggs of rats exposed to stress before conception — and found enhanced expression of the gene CRF-1.

In the second part of the study, researchers examined the brains of newborn rats immediately upon birth, before the mother could have any influence — and found enhanced expression of the gene CRF-1.

In the third part of the study, researchers exposed the offspring – both from mothers who had been exposed to stress and those who had not – to stress when they reached adulthood.

It emerged that the expression of CRF-1 among the offspring was dependent on three factors: the sex of the offspring, the stress undergone by the mother, and the stress to which the adult offspring were exposed.

Female rats whose mothers had been exposed to stress and who themselves underwent a "stressful" behavioral test showed higher levels of CRF-1 than other groups.

"This is the first time that we showed that the genetic response to stress in rats is linked to the experiences their mothers underwent long before they even got pregnant with them," the researchers said. "We are learning more and more about intergenerational genetic transfer and in light of the findings, and in light of the fact that in today's reality many women are exposed to stress even before they get pregnant, it's important to research the degree to which such phenomena takes place in humans."

Original press release:http://www.eurekalert.org/pub_releases/2013-07/uoh-ets070813.php