Increased fetoplacental angiogenesis during first trimester in anaemic women.

BACKGROUND: Epidemiological studies describe an association between relative size of the placenta at delivery and cardiovascular morbidity and mortality during adult life. Some determinants of placental size, such as maternal anaemia, have been acknowledged, but no plausible mechanism has been advanced to explain the initiation of postnatal disease.
METHODS: Placental villous vascularisation in anaemic women (Hb<90 g/L) was assessed in the first and third trimesters of pregnancy by immunohistochemical identification of villous capillaries and compared with that of gestational age-matched groups of women with normal (Hb>110 g/L; control group) concentrations of haemoglobin, and an intermediate group (Hb 90-110 g/L).
FINDINGS: Anaemia, especially in the first trimester, was associated with increased numbers of capillaries per villous cross section (mean 11.70 [SE 0.35] vs 4.14 [0.27]) located mainly in the outer third of the stroma beneath the trophoblast (94% [1.15] vs 67% [1.82]) and with increased numbers of villous macrophages and of proliferating MIB-1-positive cells compared with the control group.
INTERPRETATION: Maternal anaemia in early pregnancy seems to influence the pattern of placental vascularisation. Such changes might alter placental vascular impedance during early fetal life, thereby exerting important effects on cardiovascular development.