Infant lung function and maternal physical activity in the first half of pregnancy

Abstract

Background and aim: Physical activity (PA) in pregnancy is important for maternal and possibly offspring health. To study the early origins of lung function we aimed to determine whether PA in the first half of pregnancy is associated with lung function in healthy 3-month-old infants.

Methods: From the general population-based Preventing Atopic Dermatitis and Allergies in Children birth cohort recruiting infants antenatally in Norway and Sweden, all 812 infants (48.8% girls) with available tidal flow-volume measures in the awake state at 3 months of age and mid-pregnancy data on PA were included. PA was self-reported by the mothers and, based on intensity, we categorised them as active or inactive during pregnancy. Furthermore, we defined active mothers as fairly or highly active. The main outcome was a ratio of time to peak tidal expiratory flow to expiratory time (t _PTEF/t _E) <0.25. Associations were analysed by logistic regression, adjusting for maternal age, education, parity, pre-pregnancy body mass index, in utero nicotine exposure and parental atopy.

Results: The mean±sd t _PTEF/t _E was 0.391±0.08 and did not differ significantly according to maternal PA level in pregnancy. The 290 infants of inactive mothers had higher odds of having t _PTEF/t _E <0.25 compared to infants of all active mothers (OR 2.07, 95% CI 1.13-3.82; p=0.019) and compared to infants (n=224) of fairly active (OR 2.83, 95% CI 1.26-7.24; p=0.018) but not highly active mothers (n=298).

Conclusion: Based on self-reported maternal PA in the first half of pregnancy, 3-month-old infants of inactive compared to active mothers had higher odds of a low t _PTEF/t _E.

FIGURE 1

Study population. The present study population includes all 812 infants from the Preventing Atopic Dermatitis and Allergies in Children (PreventADALL) cohort with a successful tidal flow–volume (TFV) measurement in the awake state at 3 months of age and available information on maternal physical activity in the first half of pregnancy. To ensure independency of all participants, the second-born twin was consecutively excluded.

FIGURE 2

Histograms showing the distribution of the infant ratio of time to peak tidal expiratory flow to expiratory time (t_PTEF/t_E) in a) all included infants (n=812) and b) infants of inactive (n=290) compared to all active (n=522) mothers, presented with partly overlapping bars. While the y-axis in a) shows frequency, the two overlapping histograms in b) have percentage on the y-axis to enable comparison of the distribution of infant t_PTEF/t_E in subgroups of different size.

FIGURE 3

Infant ratio of time to peak tidal expiratory flow to expiratory time (t_PTEF/t_E) at 3 months of age according to maternal general activity level, shown for infants of a) inactive and active mothers, and b) inactive, fairly active and highly active mothers. Mean t_PTEF/t_E for infants of inactive and active mothers was compared with the independent sample t-test (p=0.321), and for infants of inactive, fairly active and highly active mothers, with one-way ANOVA (p=0.594). No statistically significant difference was observed between the groups. Symbols represent means and whiskers represent 95% confidence intervals.

FIGURE 4

Infant a) tidal volume (V_T) corrected for body weight and b) respiratory rate at 3 months of age according to maternal general activity level in three categories. a) Mean V_T corrected for body weight was compared between groups with one-way ANOVA (p=0.023). Mean V_T corrected for body weight differed significantly between infants of fairly active and highly active mothers (mean difference 0.47 mL·kg⁻¹, 95% CI 0.026–0.905 mL·kg⁻¹; p=0.035). b) Mean respiratory rate was compared between groups with one-way ANOVA (p=0.053). Mean respiratory rate differed significantly between infants of highly active and fairly active mothers (mean difference 2.84, 95% CI 0.09–5.59 breaths per min; p=0.041). Symbols represent means and whiskers represent 95% confidence intervals.