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According to new research from the University of Cambridge, the sex of a baby controls the level of metabolites in the pregnant mother’s blood, which may explain why risks of some diseases in pregnancy vary depending whether the mother is carrying a boy or a girl.
Male fetus may be more vulnerable to the effects of poor growth, while carrying female fetus may lead to an increased risk of severe pre-eclampsia for the mother. A team led by researchers at the Department of Obstetrics and Gynaecology, NIHR Cambridge Biomedical Research Centre, performed detailed scientific studies on first time mothers and analysed samples of placenta and maternal blood.
They found that the genetic profile of the placentas of male and female fetuses were very different in relation to the baby’s sex. Many of the genes that differed according to the sex of the fetus in the placenta had not previously been seen to differ by sex in other tissues of the body. One of these uniquely sex-related placental genes controlled the level of spermine. Spermine is a metabolite, a substance involved in metabolism that plays an important role in all cells and is even essential for the growth of some bacteria.
Female placentas had much higher levels of the enzyme that makes spermine, and mothers pregnant with girls had higher levels of a form of spermine in their blood compared to mothers pregnant with baby boys. Placental cells from boys found to be more susceptible to the toxic effects of a drug that blocked spermine production. This provided direct experimental evidence for sex-related differences in the placental metabolism of spermine.
The form of spermine which was higher in mothers pregnant with a girl was also predictive of the risk of pre-eclampsia – where the mother develops high blood pressure and kidney disease, whereas low levels were associated with an increased risk of poor fetal growth. These differences alter elements of the composition of the mother’s blood and may modify her risk of pregnancy complications.
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