Scientists Discover Muscular 'Switch' That Controls Birth Contractions

Dr. Enrique Jacome

In a world first, researchers in Australia have discovered an electrical switch in the uterus that does not seem to work properly in overweight pregnant women and may help explain the high rates of cesarean delivery in this group.

The study, led by Helena Parkington, an associate professor in the Faculty of Medicine, Nursing & Health Sciences at Monash University in Melbourne, is published in the journal Nature Communications.

After examining muscle biopsies taken from the uterus of 70 women, the team found an ion channel that sends electrical signals and controls contractions of the uterus.

Prof. Parkington says the switch needs to be turned off for birth contractions to begin, but in overweight women it appears to remain turned on, as she explains:

"The reason it stays on is that the 'molecular hand' that should turn the switch off fails to appear in sufficient quantities in the uterine muscle of overweight women when labor should be occurring."

In their study paper, the researchers describe how the ion channel - a potassium channel called hERG - suppresses contractions before labor. The 'molecular hand' is an inhibitory protein that is markedly enhanced during labor, "resulting in reduced hERG activity that is associated with an increased duration of uterine action potentials and contractions."

Overweight women have low levels of protein that turns the switch off

They note that changes in channel activity contribute to "electrophysiological mechanisms" that produce contractions during labor. In their study, they showed this system fails in overweight women, whose hERG channel remains active as a result of low levels of the inhibitory protein.

For example, it should be possible to develop a drug that acts like the molecular hand and turns the switch on so labor and birth can progress normally.

The team believes the discovery significantly improves our understanding of how labor and birth progress, and why women have complicated labors. It should be possible now to develop safe, effective and specific treatments to correct the problem.

Overweight pregnant women often go over their due date or have a slow labor once it begins. They also need more medical help with labor and birth and have higher rates of birth induction and cesarean section - due to failure to progress in labor.

Medical News Today recently reported a study led by Imperial College London that showed how high maternal BMI is linked to poor pregnancy outcomes. The study found that even small increases in maternal BMI were linked to a higher risk of fetal death, stillbirth, neonatal death, perinatal death and infant death.

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