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Foramen ovale changes in growth-restricted fetuses
T Kiserud1, G Chedid, S Rasmussen
1Institute of Clinical and Molecular Medicine, Division of Obstetrics & Gynecology, University of Bergen, Bergen, Norway. torvid.kiserud@kk.uib.no
Summary
Growth-restricted fetuses have smaller foramen ovale (FO) sizes, especially before 32 weeks gestation. This reduced FO size, particularly relative to the right atrium, suggests impaired fetal shunting in cases of placental compromise.
Area of Science:
- Fetal physiology
- Cardiovascular development
- Perinatal medicine
Background:
- Hypoxemia in animal models increases shunting through the fetal foramen ovale (FO).
- This suggests the FO may expand to accommodate increased blood flow.
- The size and function of the FO in human growth-restricted fetuses remain unclear.
Purpose of the Study:
- To investigate the hypothesis that the FO is expanded in growth-restricted human fetuses.
- To determine the size of the foramen ovale (FO) in fetuses experiencing intrauterine growth restriction (IUGR).
Main Methods:
- Thirty-one growth-restricted fetuses (<5th percentile) were studied between 24-39 weeks gestation.
- Foramen ovale (FO) diameter and right atrium (RA) transverse diameter were measured.
- Umbilical artery pulsatility index (PI) was assessed to evaluate placental function.
Main Results:
- Growth-restricted fetuses exhibited a smaller FO diameter compared to controls (P=0.002).
- The relative FO size (FO/RA ratio) was significantly reduced in growth-restricted fetuses (P<0.0001).
- This reduction was most pronounced before 32 weeks gestation and correlated with placental compromise.
Conclusions:
- Growth-restricted fetuses maintain normal heart size (RA diameter) but have a reduced FO diameter.
- The impaired FO shunting is evident before 32 weeks gestation.
- This finding supports the theory of compromised FO shunting in fetuses with placental insufficiency.