Sex, drugs and rock and roll: tales from preterm fetal life
Premature fetuses and babies are at greater risk of mortality and morbidity than their term counterparts. The underlying causes are multifactorial, but include exposure to hypoxia. Immaturity of organs and their functional control may impair the physiological defence responses to hypoxia and the pre...
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| Published in: | The Journal of physiology 2017-03, Vol.595 (6), p.1865-1881 |
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| Main Author: | |
| Format: | Article |
| Language: | eng |
| Subjects: | |
| Online Access: | Get full text |
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| Summary: | Premature fetuses and babies are at greater risk of mortality and morbidity than their term counterparts. The underlying causes are multifactorial, but include exposure to hypoxia. Immaturity of organs and their functional control may impair the physiological defence responses to hypoxia and the preterm fetal responses, or lack thereof, to moderate hypoxia appear to support this concept. However, as this review demonstrates, despite immaturity, the preterm fetus responds to asphyxia in a qualitatively similar manner to that seen at term. This highlights the importance in understanding metabolism versus homeostatic threat when assessing fetal responses to adverse challenges such as hypoxia. Data are presented to show that the preterm fetal adaptation to asphyxia is triphasic in nature. Phase one represents the rapid institution of maximal defences, designed to maintain blood pressure and central perfusion at the expense of peripheral organs. Phase two is one of adaptive compensation. Controlled reperfusion partially offsets peripheral tissue oxygen debt, while maintaining sufficient vasoconstriction to limit the fall in perfusion. Phase three is about decompensation. Strikingly, the preterm fetus generally performs better during phases two and three, and can survive for longer without injury. Paradoxically, however, the ability to survive can lead to longer exposure to hypotension and hypoperfusion and thus potentially greater injury. The effects of fetal sex, inflammation and drugs on the triphasic adaptations are reviewed. Finally, the review highlights the need for more comprehensive studies to understand the complexity of perinatal physiology if we are to develop effective strategies to improve preterm outcomes.
This graphical demonstrates the triphasic responses of the fetus to asphyxia and outlines the key features in each phase, and how fetal exposure to magnesium sulphate (MgSO4) and inflammation may modify these responses. The phases of adaptation to asphyxia can be thought of by the colour coding of a traffic light: phase one is green for maximal defence responses, which ensure that fetuses of all ages will survive and probably without any injury. Phase two is coded orange for warning. This phase constitutes a secondary adaptation to asphyxia where maximal defences such as total peripheral vasoconstriction must be tempered if peripheral organs are to survive. This comes at the cost of controlling perfusion. Phase three is about decompensation. A |
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| ISSN: | 0022-3751 1469-7793 |