HDCN Article Review/Hyperlink

Churchill D, Perry IJ, Beevers DG

Ambulatory blood pressure in pregnancy and fetal growth

Lancet (Jan) 349:7-10 1997

Barker et al in 1990 (BMJ 301:259-262, 1990) made the observation that low birthweight infants tended to develop both hypertension and other cardiovascular disease later in life. The mechanism of this association has not been defined. One potential observation of this finding is possible relation between maternal risk factors such as obesity, smoking, and blood pressure, and intrauterine growth. Previously a relation between maternal hypertension and birthweight had been discounted.

In this study, Churchill and colleagues examined the relation between maternal blood pressure at 18, 28, and 36 weeks gestation vs. birth weight. At 28 and 36 weeks' gestation, there was an inverse relationship between ambulatory diastolic (but not systolic) BP and later birthweight, such that at 28 weeks gestation, mothers with diastolic ambulatory BP values of 56-62 mm Hg gave birth to infants weighing 3364 g, whereas when the same BP was 74-81 mm Hg, mean birthweight was 2889 g. This association remained after multivariate analysis controlling for smoking, alcohol intake, ethnic origin, pregnancy hypertension syndromes, and preterm birth. Interestingly, there was no association between clinic BP measurements and birthweight in the same population.

Comment: The results have two implications. First, they point to the value of ambulatory BP readings in pregnant patients. Second, this association weakens somewhat the need for theories explaining the association between low birth weight and cardiovascular disease based on intrauterine growth retardation. The case might have been stronger, however, if this association were also present with maternal BP measured in the non-gravid state. At 18 weeks gestation, for example, no relation was found between maternal BP and ultimate infant birthweight. The authors imply that their results point to a presumably genetic association between low birthweight and maternal hypertension, and therefore between hypertension in parent and offspring. Non-gravid ambulatory BP measurements would be required to make this case convincingly. Otherwise, some factor which results in low birthweight in the infant may be acting to increase the BP late in pregnancy, and the intrauterine growth retardation hypothesis may still hold. (John T. Daugirdas, M.D., University of Illinois at Chicago)