Sleep disordered breathing describes a group of conditions involving abnormal respiratory patterns during sleep, with the spectrum ranging from snoring to complete obstruction of the upper airway and hypoventilation. In obstructive sleep apnea (OSA), recurrent episodes of airway obstruction may be associated with oxygen desaturation or arousal from sleep, along with acute changes in heart rate and blood pressure [1]. This cyclical pattern has been associated with sympathetic activation, oxidative stress, and elevations in proinflammatory cytokines as well as endothelial dysfunction [2], [3], [4], [5]. Accordingly, in the non-pregnant population, OSA is consistently linked to hypertension [6], cardiovascular diseases [7], [8], [9], and metabolic dysfunction [10].

In pregnancy, OSA and preeclampsia have been shown to be strongly associated [11], [12], [13], [14], [15]. Common risk factors – including obesity, diabetes mellitus, chronic hypertension, and maternal age over 35 years – may partially explain the inter-relation between these two conditions [16]. OSA may also contribute to increased peripheral vascular resistance and hypertension through lack of normal vascular reactivity of the maternal uterine arteries, increased sympathetic activation, and anti-angiogenic factor release [16], [17]. As a result, OSA may induce or possibly further exacerbate the widespread endothelial dysfunction seen in preeclampsia [16], [18], [19], potentially leading to an increased risk of adverse outcomes. Accordingly, OSA is associated with an increased risk of severe maternal morbidity, including cardiovascular complications such as pulmonary edema and acute heart failure [11], [12], [20].

Although several studies have estimated the incidence and the risk of preeclampsia among pregnant women with snoring and OSA [11], [12], [13], [14], [16], two studies, with limited sample sizes, have reported inconsistent findings of the effect of OSA on maternal morbidity outcomes among women with hypertensive disorders of pregnancy [21], [22]. In the first study (n = 85), OSA was not associated with increased blood pressure severity or worsened anti-angiogenic profile in pregnant participants with hypertensive disorders [21]. In the second study (n = 100), the severity of OSA among participants with gestational hypertension and preeclampsia was correlated with blood pressure values, independently from maternal weight [22]. Therefore, the impact of OSA on severe maternal morbidity, and specifically severe cardiovascular morbidity, among women with preeclampsia remains unclear. Our aim was to assess whether OSA is associated with an increased risk of severe maternal morbidity, and in particular severe cardiovascular morbidity, in a large population-based cohort of women with preeclampsia. In addition, since maternal morbidity can lead to increased healthcare resource requirements, we sought to assess the impact of OSA on healthcare utilization among women with preeclampsia. We hypothesized that women with preeclampsia and concomitant OSA had a higher risk of severe maternal morbidity, severe cardiovascular morbidity, and healthcare utilization than those without OSA.