Late Breaking Abstract - Fetal thoracic circumference in mid-pregnancy and infant lung function

Abstract

Background and Aim: Impaired lung function in early infancy is associated with later wheeze and asthma, while fetal thoracic circumference (TC) may predict severity of neonatal lung hypoplasia. To explore fetal origins of aberrant lung development we aimed to determine if mid-pregnancy fetal TC was associated with lung function in healthy 3-month old infants.

Methods: From the Scandinavian general population-based PreventADALL birth cohort (n=2701), 716 infants had ultrasound measures of TC at around 18 weeks gestational age (GA) and tidal flow volume measures in the awake state at three months of age. Fetal TC correlates strongly with fetal age, estimated by head circumference (HC). Thus, the association between the ratio TC/HC and infant time to Peak Tidal Expiratory Flow to Expiratory time (t_PTEF/t_E) was analyzed, by linear regression. Maternal asthma, infant sex, GA at birth, birthweight, postnatal age in days, weight, length, respiratory rate, time since last feeding and if the infant had ever been examined for respiratory symptoms were included as covariates. Outcomes were a t_PTEF/t_E <0.25 or in the lowest 10, 25 or 50 percentiles as well as t_PTEF/t_E as a continuum.

Results: The infants were 47.5% girls. The mean (min, max) GA at birth was 40.2 (35.3, 42.4) weeks and weight at three months 6.3 (4.4, 8.9) kg. The mean (min, max) TC/HC was 0.75 (0.61, 0.93) and t_PTEF/t_E 0.39 (0.19, 0.60). Five infants had a t_PTEF/t_E <0.20 while 10% had a t_PTEF/t_E <0.28. Fetal TC/HC was not associated with t_PTEF/t_E in simple regression models (p-values 0.10-0.22) or when adjusted for covariates (p-values 0.38-0.83).

Conclusion: Fetal TC/HC in mid-pregnancy was not associated with t_PTEF/t_E in healthy awake 3-month old infants.