Interpretation
Previous studies have demonstrated significant reductions in pulmonary functional reserves in SCD 2,4. Also, existing data show strong associations between reduction in FEV1% predicted and SCD-related morbidity and mortality23–25. What remains unclear is whether reduction in pulmonary function in pregnant women with SCD is associated with adverse pregnancy outcomes. The results of our study suggest that in pregnant women with SCD, low FEV1% predicted is associated with an increased risk of fetal death
In the general population, low FEV1% predicted or decline in FEV1 has been shown to be associated with mortality 21,24–28. Also in the general population, FEV1% predicted is a known robust predictor of sudden cardiac death, with the relationship independent of cardiac function26,28. In addition our team has previously demonstrated that low FEV1% predicted is a predictor of earlier death in young adults with SCD and future ACS episodes27.
Prior studies have indicated that low FEV1% predicted during pregnancy is associated with adverse perinatal outcome in pregnant women with cystic fibrosis 21,22,29,30; however, the biological basis for this association has not been elucidated. Reynaud et al . have reported that pregnancy in women with cystic fibrosis and poor pulmonary function has a negative impact on fetal growth 21. Other retrospective analyses of pregnancies in women with cystic fibrosis have further highlighted low maternal baseline FEV1% predicted as a predictor of premature delivery, LBW and fetal death 22,29,30. These findings in pregnant women with cystic fibrosis lend credence to the biological plausibility that observed association between lower FEV1% predicted and fetal death in SCD.
We found no significant association between low maternal FEV1% predicted and adverse maternal outcomes including ACS, acute painful episodes and maternal deaths. Although we found no statistical difference between the rates of acute painful episodes, ACS, and deaths in women with baseline FEV1% predicted ≥ 65 and those with FEV1% predicted < 65, the mean events per patient year for acute pain episodes and ACS, and maternal mortality were higher (33%, 150%, and 370% respectively) in the group with FEV1% predicted < 65, compared to the group with FEV1% predicted ≥ 65. The lack of statistically significant difference in our study may be due to limited power or the natural short follow-up period during pregnancy. These limitations can be overcome with larger multi-center prospective studies.