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Updated: May 24, 2026
The Perinatal Asphyxiated Lamb Model: A Model for Newborn Resuscitation
Published on: August 15, 2018
The cardiopulmonary haemodynamic transition at birth is not different between male and female preterm lambs
Graeme R Polglase1, Stuart B Hooper, Martin Kluckow
1The Ritchie Centre, Monash Institute of Medical Research, Monash University, Clayton, Vic. 3168, Australia. graeme.polglase@monash.edu
Insights
Preterm male lambs do not show sex-based differences in cardiovascular transition at birth. This suggests the neonatal male disadvantage is not due to impaired cardiopulmonary adaptation immediately after birth.
Area of Science:
- Neonatal physiology
- Cardiopulmonary adaptation
- Sex differences in preterm infants
Background:
- Preterm males face higher mortality and morbidity than females, primarily from respiratory issues.
- This increased risk is particularly evident in the hours following birth.
- The underlying causes for this neonatal 'male disadvantage' remain unclear.
Purpose of the Study:
- To investigate if sex-based differences in cardiopulmonary transition influence male morbidity after preterm birth.
- To determine if cardiovascular adaptation differs between male and female preterm lambs.
- To explore the role of immediate postnatal cardiopulmonary hemodynamics in sex-based preterm outcomes.
Main Methods:
- Surgically implanted pulmonary arterial flow probes and catheters in preterm lambs before delivery.
- Ventilated and anesthetized lambs for 30 minutes post-birth.
- Real-time recording of arterial pressures and flows, with Doppler echocardiography for left-ventricular output measurement.
Main Results:
- No significant differences in fetal or neonatal sex-based cardiopulmonary hemodynamics, blood gases, or ventilation parameters were observed.
- Pre-birth fetal measurements showed no sex-based variations in hemodynamics, blood gases, pH, glucose, or lactate.
- Postnatal assessments revealed no significant sex-based differences in arterial blood gas status, ventilation, respiratory indices, or cardiopulmonary hemodynamics.
Conclusions:
- Neonatal sex does not influence the cardiopulmonary transition in ventilated, anesthetized preterm lambs.
- The observed neonatal 'male disadvantage' in preterm infants is not explained by impaired cardiovascular transition at birth.
- Further research is needed to identify the specific factors contributing to increased male morbidity after preterm birth.
Abstract:
Males born preterm are at greater risk of illness and death than females, principally due to respiratory disease. Much of the excess morbidity occurs within the first few hours of life. Therefore, the aim of the present study was to investigate whether or not differences in the cardiopulmonary transition soon after birth underlie the increased morbidity in males after preterm birth. Nine female and thirteen male lambs (128±2 days gestation) underwent surgery immediately before delivery for implantation of a pulmonary arterial flow-probe and catheters into the main pulmonary artery and a carotid artery. After birth lambs were ventilated for 30 min (tidal volume 7 mL kg(-1)) while anaesthetised. Arterial pressures and flows were recorded in real time and left-ventricular output measured using Doppler echocardiography. Before birth, fetal cardiopulmonary haemodynamics, arterial blood gases, pH, glucose and lactate did not differ between sexes. Similarly, in the neonatal period there were no significant differences in arterial blood gas status, ventilation parameters, respiratory indices or cardiopulmonary haemodynamics between the sexes. Our data show that the cardiopulmonary transition at birth in ventilated, anaesthetised preterm lambs is not influenced by sex. Thus, the neonatal 'male disadvantage' is not explained by an impaired cardiovascular transition at birth.
