Rapid Responses to:

PAPERS: N R Poulter, C L Chang, A J MacGregor, H Snieder, and T D Spector Association between birth weight and adult blood pressure in twins: historical cohort study BMJ 1999; 319: 1330-1333 [Abstract] [Full text]

Rapid Responses: Submit a response to this article

Rapid Responses published:

Blood pressure, birth, birth weight

Walter Holland   (29 November 1999)

Reduced arterial distensibility in the fetus may link placental dysfunction in utero and later blood

Helena Gardiner, Y F Cheung   (16 December 1999)

Blood pressure, birth, birth weight 29 November 1999
Walter Holland Send response to journal: Re: Blood pressure, birth, birth weight	Editor - Recent articles in the BMJ associate high blood pressure in children and adults with low birth weight (1, 2, 3). None of these articles nor others making similar statements, appear to be aware of work done 40 years ago (4, 5), which showed that several factors influenced levels of systolic blood pressure at birth, including maturity, birth weight and conditions at birth. The findings at birth were very different (low birth weight was associated with low pressure) to those reported most recently. Another study showed the need to take into account cuff size and method of measurement.(6) It is quite possible that there were errors of judgement in our studies (4, 5), but conditions during and after birth were carefully observed in contrast to reliance on routine records, with all their problems. It is unfortunate that measures now do not appear to consider relevant studies done in the past - particularly before the advent of computerised data retrieval methods such as Medline, and therefore do not consider it necessary to consider non-confinement findings relevant. I have no ready explanation for the differences between our findings and current publications, but do think that it is important to explore the possible reasons for the differences in results found. Walter Holland, visiting professor, LSE Health London School of Economics & Political Science, London WC2A 2AE 1. Law C M, de Swiet M, Osmond C, Fayers P M, Cruddas A M, Fall C H, "Initiation of Hypertension in Utero and Amplification Throughout Life", BMJ 1993;306:24-7. 2. Dwyer T, Leigh Blizzard R M, Ponsonby A L, "Within Pair Association Between Birth Weight and Blood Pressure at ages 8 in Twins from a Cohort Study", BMJ 1999;319:1325-1329. 3. Poulter N R, Chang C L, MacGregor A J, Snieder H, Spector T D, "Association Between Birth Weight and Adult Blood Pressure in Twins: Historical Cohort Study", BMJ 1999; 319:1330-1333. 4. Holland W W, Young I M, "Neonatal Blood Pressure in Relation to Maturity, Mode of Delivery, and Condition at Birth", BMJ 1956;2:1331. 5. Young I M, Holland W W, "Some Physiological Responses of Neonatal Arterial Blood Pressure and Pulse Rate", BMJ 1958; 2:276-278. 6. Long M, Dunlop J R, Holland W W, "Blood Pressure Recording in Children", Arch. Dis. Childhood 1971;46:636-640.
Reduced arterial distensibility in the fetus may link placental dysfunction in utero and later blood 16 December 1999
Helena Gardiner, Senior Lecturer in Perinatal Cardiology Department of Materno-Fetal Medicine, Imperial College, London, Y F Cheung Send response to journal: Re: Reduced arterial distensibility in the fetus may link placental dysfunction in utero and later blood	EDITOR – We support the conclusions of recent contributors Dwyer et al(1) and Poulter et al(2) who suggest that intertwin differences in blood pressure, seen in childhood and later in life, were more likely to be due to dysfunction of the fetoplacental unit rather than to maternal malnutrition or to genetic predisposition. Nonetheless, their data fail to provide an explanation for the proposed link between placental dysfunction and programming of blood pressure in utero. We hypothesize that one of the underlying mechanisms is related to alteration of arterial distensibility during the fetal period. We have reported on reduced distensibility of the peripheral conduit arteries in the growth-restricted monochorionic donor twins in twin-twin transfusion syndrome (TTTS) during infancy(3). This syndrome is an ideal model in which to assess within pair differences in the cardiovascular response in two genetically identical individuals due to volume load and increased placental resistance acting on the developing cardiovascular system. In singletons with intrauterine growth restriction due to placental insufficiency, the resistance of the placenta and vasculature in the lower body is increased thereby sparing cerebral perfusion. The resultant decrease in blood flow is manifest in alteration of the properties of the fetal arterial vessel wall pulsation (4) and may initiate permanent structural changes in the descending aorta and lower limbs arteries that explain the observed reduction of arterial compliance of the conduit arteries of the trunk and lower limbs in these individuals later in life (5). In the TTTS donor fetuses, such reduction in arterial blood flow is exaggerated by hypovolaemia as a result of net transfusion of blood to the recipient fetuses. Although the relationship between reduction in blood flow and vascular development is not fully clear, the end result of reduced arterial distensibility certainly has important implications. Reduced arterial distensibility contributes to the pathogenesis of hypertension. The arterial characteristic impedance is reduced, pulse pressure increased and the pulsatile cardiac workload accentuated. Furthermore, increase in pulse wave velocity results in early return of the reflected wave and augments the systolic pressure. We echo the comments of Dwyer et al. (1) that the future direction of research in this topic should focus on factors within the fetoplacental unit, and propose that alteration of arterial distensibility may be the link between placental dysfunction in utero and higher blood pressure later in life. References 1 Dwyer T, Blizzard L, Morley R, Ponsonby AL. Within pair association between birth weight and blood pressure at age 8 in twins from a cohort study. BMJ 1999;319:1352-9. 2 Poulter NR, Chang CL, MacGregor AJ, Sneider H, Spector TD. Association between birth weight and adult blood pressure in twins: historical cohort study. BMJ 1999;319:1330-3. 3 Cheung YF, Taylor MJO, Fisk NM, Redington AN, Gardiner HM. Fetal origins of reduced arterial distensibility in the donor twin in twin-twin transfusion syndrome. Lancet (in press). 4 Gardiner,H.M.; Kopecka,J.; Stale,H; Marsal,K. Fetal Vascular Programming: Aortic Biophysical Properties Differ in Growth Restriction. Proceedings of the second World Congress in Paediatric Cardiology and Cardiac Surgery, Futura 1998;110-111. 5 Martyn CN, Barker DJP, Jespersen S, Greenwald S, Osmond C, Berry C. Growth in utero, adult blood pressure, and arterial compliance. Br Heart J 1995;73:116-21.