Massive decline in lung liquid before vaginal delivery at term in the fetal lamb

https://doi.org/10.1016/S0002-9378(98)80004-5Get rights and content

Objective: Our aim was to determine the volume of liquid remaining in the lungs of the fetal lamb just before a normal vaginal delivery at term to assess the extent to which an excess of liquid in the airspaces might contribute to the respiratory morbidity that accompanies elective cesarean delivery.

Study Design: The volume of liquid in the future airspace of the lungs was determined at the end of labor in eight fetal lambs at term from the dilution of an impermeable tracer (125I-labeled human serum albumin) mixed into the liquid. This volume was compared with that measured in a second group of 10 fetal lambs studied 7 days before the expected date of delivery (term=147 days).

Results: The volume of lung liquid present at the end of labor was 6.8 ± 1.0 ml · kg−1 (n=8) compared with 28.2±1.8 ml · kg−1 (n=10) in the second group of lambs studied before the onset of labor at 140 days of gestation.

Conclusion: Our results indicate that the bulk (>75%) of the liquid that fills the lungs of the fetal lamb at 140 days of gestation is cleared at some time before normal term birth, suggesting that the adverse respiratory impact of elective cesarean delivery may be largely explained by denying the fetus this important adaptive mechanism.

References (25)

  • DicksonKA et al.

    Decline in lung liquid volume before labor in fetal lambs

    J Appl Physiol

    (1986)
  • KittermanJA et al.

    Tracheal fluid in fetal lambs: spontaneous decrease prior to birth

    J Appl Physiol

    (1979)
  • Cited by (31)

    • Establishing functional residual capacity in the non-breathing infant

      2013, Seminars in Fetal and Neonatal Medicine
      Citation Excerpt :

      However, whether or not lung liquid secretion rates and volumes decrease before labour onset is controversial. Some studies have reported a decrease [14–16], whereas others [17] have found no change if the pregnancy is not complicated by a reduction in amniotic fluid volumes. Furthermore, it is unclear how reductions in lung liquid secretion rates could reduce lung liquid volumes, as reductions in secretion rates simply reduce liquid loss via the trachea, resulting in no change in liquid volumes [9,10].

    • Elective Cesarean Section: Its Impact on Neonatal Respiratory Outcome

      2008, Clinics in Perinatology
      Citation Excerpt :

      We are still far from a complete understanding of the mechanisms by which fetal lungs are able to clear themselves of excessive fluid at birth [81]. It is clear, though, that traditional explanations relying on “Starling forces” and “vaginal squeeze” can only account for a fraction of the fluid absorbed [71,82–86]. Amiloride-sensitive sodium transport by lung epithelia through epithelial sodium channels (ENaC) has emerged as a key event in the transepithelial movement of alveolar fluid [72,74,75,78–80,87–90].

    • Expulsion of liquid from the fetal lung during labour in sheep

      2007, Respiratory Physiology and Neurobiology
    • Hypoxic Respiratory Failure in the Late Preterm Infant

      2006, Clinics in Perinatology
      Citation Excerpt :

      Understanding of the mechanisms(s) by which fetal lungs are able to clear themselves of excessive fluid at birth remains far from complete. It is clear though, that traditional explanations that relied on Starling forces and vaginal squeeze can account for only a fraction of the fluid absorbed [13–18]. Amiloride-sensitive sodium transport by lung epithelia through epithelial sodium channels (ENaC) has emerged as a key event in the transepithelial movement of alveolar fluid [19–27], and this appears to be a two-step process.

    View all citing articles on Scopus

    Supported by the National Health and Medical Research Council of Australia and the Windermere Foundation

    View full text