Pregnancy advice: Is morning sickness a good sign?
I'm 10 weeks pregnant and feel really sick a lot of the time, especially when I smell cigarette smoke. I've had a miscarriage before, and I'm worried feeling ill could be a sign that the pregnancy is 'bad'. Am I right to be frightened?
"I appreciate it seems strange to say this, but all the evidence indicates you shouldn't be frightened at all.
"In a 2016 US study of almost 800 women who'd had at least one miscarriage and then became pregnant again, when nausea and vomiting was common in early pregnancy it was associated with a reduced risk of pregnancy loss.
"There's now a credible scientific explanation for this, thanks to a hormone called endokinin, which the placenta produces. Endokinin acts to improve both the local blood flow and the changes needed where the placenta and the uterus knit together to ensure efficient transfer of nutrients and gases necessary for a healthy baby.
" Unfortunately, when this placental endokinin spills into your circulation it can stimulate the vomiting centre in your brain.
"The nausea experienced during smoke inhalation is due to endokinin from the lungs. In pregnancy, this lung endokinin circulates through the uterine vasculature - although it cannot enter the placenta - and its presence interferes with the local beneficial effects of placental endokinin.
"This explains why smoking leads to a poor pregnancy outcome, and why women who smoke and are intending to get pregnant should kick the habit well beforehand, and certainly not smoke during pregnancy."
Professor Philip Lowry of Reading University's School of Biological Sciences has reviewed the role of certain hormones in morning sickness, and the effect of smoking at this time