Rationale: Survival and longevity in patients with cystic fibrosis (CF) have
improved with new treatments, so that pregnancy can be safely undertaken
despite physiologic limitations. Dyspnea still develops in the latter stages of
pregnancy. To explain this symptom, we evaluated the effect of pregnancy on
lung function before and after delivery. Methods: Records of 23 pregnant
patients with CF were retrospectively reviewed for data analysis. Spirometry
was recorded prior to pregnancy, at first and third trimesters, and every three
months following delivery up to one year. Comparisons between time points were
adjusted for age and pre-gestational BMI by analysis of variance (ANOVA). Results: Complete clinical and spirometric data were available for eleven of these
patients (13 pregnancies total), obtained between 2009 and 2017. FEV1 and FVC
declined significantly from baseline to third trimester (by 8.1%, p < 0.043
and 9.3%, p < 0.013, respectively). No statistically significant differences
amongst spirometric values were observed, however, when adjusted for BMI and
age over the entire time course. FEV1 and FVC recovered to baseline six months
and one year following delivery, respectively. Conclusions: The changes
in FEV1 and FVC occur as a result of increases in intravascular blood volume
and lung water during the third trimester. At the same time, FEV1/FVC increases as there
is reversal of bronchiolar constriction with elimination of extracellular fluid
and lung water. Furthermore, restoration of end-expiratory lung volume
post-partum counteracts reversal of air trapping with resolution of
peribronchiolar edema, with FVC remaining unchanged. These changes would
explain decrease in dyspnea following delivery in CF patients.
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