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The feto-placental unit stimulates the pregnancy-associated increase in maternal bone metabolism
1Section of Obstetrics and Gynaecology, Imperial College School of Medicine, Chelsea and Westminster Hospital, London, UK.
Insights
The feto-placental unit significantly impacts maternal bone metabolism during pregnancy. Increased fetal numbers stimulate bone resorption, a process reversible through fetal reduction.
Area of Science:
- Reproductive Endocrinology
- Bone Metabolism
- Maternal-Fetal Medicine
Background:
- Pregnancy significantly alters maternal bone metabolism.
- The feto-placental unit's role in these changes is not fully understood.
Purpose of the Study:
- To investigate the feto-placental unit's influence on pregnancy-induced maternal bone metabolism.
- To assess bone formation and resorption markers in relation to fetal numbers.
Main Methods:
- Measured serum concentrations of carboxy terminal pro-peptide of type I pro-collagen (PICP) and cross-linked carboxy terminal telopeptide of type I collagen (ICTP).
- Studied singleton, twin, and multifetal pregnancies (≥3 fetuses) before and after selective fetal reduction.
- Collected blood samples at 10-12 weeks gestation and 4 and 8 weeks post-reduction.
Main Results:
- PICP and ICTP concentrations correlated positively with the number of fetuses.
- Multifetal pregnancies showed significantly higher PICP and ICTP levels than twin pregnancies.
- ICTP levels decreased to twin pregnancy levels post-fetal reduction, while PICP remained unchanged.
Conclusions:
- The feto-placental unit releases a factor that stimulates maternal bone resorption, particularly in higher-order multiple pregnancies.
- This factor's action is primarily on bone resorption, not formation.
- Selective fetal reduction normalizes elevated bone resorption markers.
Abstract:
The aim of the study was to investigate role of the feto-placental unit in the pregnancy-induced increase in maternal bone metabolism. To achieve this, circulating concentrations of carboxy terminal pro-peptide of type I pro-collagen (PICP, a marker of bone formation) and cross-linked carboxy terminal telopeptide of type I collagen (ICTP, a marker of bone resorption) were measured in three groups of pregnant women. Group 1 comprised 12 women with singleton pregnancies; group 2, nine women with twin pregnancies; and group 3, 19 women with multifetal pregnancies (> or =3 fetuses) before and after selective fetal reduction to twin pregnancies. Blood samples were obtained at 10-12 weeks gestation (groups 1-3, pre-fetal reduction in group 3) and 4 weeks and 8 weeks later (groups 2 and 3). Before fetal reduction there was a significant correlation between the number of fetuses and the concentrations of both PICP and ICTP (r = 0.503 and P = 0.001 and r = 0.573 and P < 0.001 respectively). The circulating concentrations of PICP and ICTP were significantly higher in the pre-reduction multifetal pregnancies than in the twin pregnancies (P < 0.001 and P = 0.0013 respectively). The circulating concentrations of ICTP in multifetal pregnancies fell by 4 weeks after fetal reduction to those observed in control twins. Concentrations of PICP were unaltered after fetal reduction. Higher order multiple pregnancies had the greatest decline in ICTP concentrations. These data suggest that the increased bone turnover observed in the multifetal pregnancies is due to a factor derived from the feto-placental unit and that this factor acts primarily to stimulate bone resorption.