Journal of Applied Physiology, Vol 76, Issue 6 2535-2540, Copyright © 1994 by American Physiological Society
Effect of maternal hypoxemia on behavior in unanesthetized normoxic or mildly hyperoxic fetal lambs
I. M. Kuipers, W. J. Maertzdorf, H. Keunen, D. S. De Jong, M. A. Hanson and C. E. Blanco
Department of Neonatology, Academic Hospital Maastricht, University of Limburg, The Netherlands.
To determine whether hypoxemia inhibits fetal activity by substances from
the mother or placenta, six fetal lambs were chronically instrumented at
128-132 days gestation for extra-corporeal membrane oxygenation (ECMO).
Severe maternal hypoxemia (arterial PO2 decreased to 6.00 +/- 0.60 kPa) was
produced while fetal arterial PO2 was maintained normoxic or mildly
hyperoxic using ECMO. The incidences of fetal breathing movements were 34.8
+/- 3.1% (SE) during baseline before ECMO, 36.8 +/- 3.4% during baseline
with ECMO, and 21.4 +/- 3.5% (P < 0.05 compared with baseline with ECMO)
during maternal hypoxemia. The durations of periods of breathing were 9.8
+/- 1.2 min before ECMO, 9.3 +/- 1.1 min with ECMO, and 10.5 +/- 1.7 min (P
= NS) during maternal hypoxemia. In 7 of 14 maternal hypoxemia experiments,
breathing activity stopped too late (7-23 min) to be attributed to maternal
hypoxemia. Fetal electrocorticographic activity (P = NS), nuchal
electromyographic activity (P = NS), and eye movements were normal before
ECMO, with ECMO, and during maternal hypoxemia. Fetal blood pressure and
heart rate did not change. We conclude that the inhibition of fetal
activity during maternal hypoxemia does not seem to be mediated by release
of factors from the maternal side of the placenta or the ewe.
