Hopes of new dawn in hunt for a morning sickness cure

A cure for morning sickness that plagues most pregnant women may be on the horizon after scientists identified what appears to be its main cause.

As many as 70 per cent of women are affected by nausea and vomiting during pregnancy. Picture: iStock

A cure for the morning sickness that plagues most pregnant women may be on the horizon after scientists identified what appears to be its main cause.

As many as 70 per cent of women are affected by nausea and vomiting during pregnancy. For some it can lead to dangerous levels of dehydration, putting their life and that of their unborn child at risk.

This condition, known as hyperemesis gravidarum, is the most common cause of women being admitted to hospital in the first three months of pregnancy. It is thought to affect between 1 and 3 per cent of expectant mothers.

Research published in the journal Nature identified the culprit as the hormone GDF15. How sick a woman feels appears to depend on a combination of how much GDF15 is produced and how much resistance her body has built up from being exposed to it before pregnancy.

The researchers believe that sickness could be avoided by gently exposing mothers to increasing levels of GDF15 before pregnancy to increase their resilience. It could even be possible to stop morning sickness after it has begun by developing an antibody drug that would block the receptors in the brain that GDF15 interacts with.

The study builds on earlier research that hinted at the role of the hormone. It shows that the degree of nausea and vomiting that a woman experiences in pregnancy is directly related to both the amount of GDF15 made by the foetal part of the placenta and sent into her bloodstream, and how sensitive she is to its nauseating effect.

Roughly speaking, the hormone interacts with a part of the brain called the area postrema. Part of the function of this region is to react to unpleasant and dangerous stimuli, such as being poisoned.

“It’s job is to say to you, ‘That’s nasty – throw up, lie in the corner and get better and never go back and do that thing again,” said Sir Stephen O’Rahilly, of the University of Cambridge, who led the research. During pregnancy, it seems to be triggered when there’s no apparent need.

GDF15 is made at low levels in all tissues outside of pregnancy. However, the team found that a rare genetic variant that puts women at a greater risk of hyperemesis gravidarum was linked to lower levels of the hormone in the blood and tissues outside of pregnancy. Similarly, women with the inherited blood disorder beta thalassemia, which causes them to have naturally very high levels of GDF15 before pregnancy, experience little or no nausea or vomiting.

Sir Stephen said the research revealed why morning sickness could be so bad for some women. “The baby growing in the womb is producing a hormone at levels the mother is not used to. The more sensitive she is to this hormone, the sicker she will become.

“Knowing this gives us a clue as to how we might prevent this from happening. It also makes us more confident that preventing GDF15 from accessing its highly specific receptor in the mother’s brain will ultimately form the basis for an effective and safe way of treating this disorder.”

The search for a treatment for morning sickness led to tragedy in the 1950s and 1960s when the drug thalidomide was used. It later became apparent that it caused severe birth defects. Sir Stephen said that targeting GDF15 looked like it should be a much safer option, in part because a foetus lacked the receptors that would react to the hormone. However, any treatment would undergo rigorous trials for side effects.

The Times