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Inherited predisposition to hypertension confounds the effect of low birthweight

BMJ 1999; 318 doi: https://doi.org/10.1136/bmj.318.7188.943 (Published 03 April 1999) Cite this as: BMJ 1999;318:943
  1. Brian R Walker, British Heart Foundation senior research fellow. (B.Walker{at}ed.ac.uk),
  2. Graham CM Watt, Professor.
  1. University of Edinburgh, Department of Medicine, Western General Hospital, Edinburgh EH4 2XU
  2. University of Glasgow, Department of General Practice, Woodside Health Centre, Glasgow G20 7LR

    EDITOR—Our study showed that the relation between lower birthweight and subsequent higher blood pressure in adulthood may be confounded by parental blood pressure.1Mothers with higher blood pressure between 9 and 19 years after delivery had babies with lower birthweight who subsequently had higher blood pressure as adults.

    Taylor et al seem to refute this finding by showing that maternal blood pressure measured during pregnancy did not confound the relation between lower birthweight and higher blood pressure in children aged 8-11 years.2 However, they have not acknowledged the weakness of measurement of maternal blood pressure in pregnancy. They do not cite a study showing that, although there is no relation between maternal blood pressure measured in the clinic during pregnancy and subsequent birthweight of the babies, an inverse relation is present across the range of normal blood pressures measured by ambulatory monitoring.3 In addition, although there is an association between pregnancy induced hypertension and essential hypertension, the two conditions are not the same. Our measurement of blood pressure in non-pregnant women is not subject to the confounding influences affecting blood pressure during pregnancy and may therefore be considered to be a closer reflection of the predisposition to hypertension which children inherit from their mothers.

    Further studies will be required to confirm or refute our observation, but Taylor et al have asked a different question, concerning pregnancy induced hypertension rather than inheritance of essential hypertension. Their negative result may reflect the imprecision of measurement of blood pressure during pregnancy.

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