Sd. Harrast et Hj. Kalkwarf, EFFECTS OF GESTATIONAL-AGE, MATERNAL DIABETES, AND INTRAUTERINE GROWTH-RETARDATION ON MARKERS OF FETAL BONE TURNOVER IN AMNIOTIC-FLUID, Calcified tissue international, 62(3), 1998, pp. 205-208
Little is known about the dynamics of bone formation and bone resorpti
on in utero, particularly the normal changes that occur throughout ges
tation and in clinical situations that result in low bone mass at birt
h. The objectives of this study were to describe the effects of gestat
ional age on markers of fetal bone turnover, and to investigate whethe
r the reported low bone mass at birth in small-for-gestational-age (SG
A) infants and infants of diabetic mothers (IDMs) was associated with
biochemical markers of decreased bone formation or increased bone reso
rption in utero. Bone formation and resorption were assessed by measur
ement of carboxyterminal propeptide of type I procollagen (PICP) and c
ross-linked carboxyterminal telopeptide of type I collagen (ICTP), res
pectively, in 201 amniotic fluid samples. These markers are by-product
s of type I collagen formation and degradation, respectively, and have
been used in the assessment of bone metabolism ex utero. Both PICP an
d ICTP concentrations in amniotic fluid were inversely associated with
gestational age (P < 0.0001). Amniotic fluid concentrations of PICP i
ncreased exponentially in relation to infant birthweight (P = 0.008),
and SGA infants had lower amniotic fluid PICP concentrations than cont
rols (P = 0.07). The presence of diabetes in the mother was not associ
ated with alterations in amniotic fluid PICP or ICTP concentrations. A
lthough maturational effects on clearance of bone markers from amnioti
c fluid cannot be excluded, these data are consistent with a high turn
over of bone matrix early in fetal life, and a reduction in bone forma
tion when fetal growth is compromised.