Both sickle cell trait and sickle cell disease were significantly associated with an increased risk of stillbirth, based on data from more than 50,000 women.
Pregnant women with sickle cell disease (SCD) are at increased risk of complications, including stillbirth, but many women with the disease in the United States lack access to specialty care, Silvia P. Canelón, PhD, of the University of Pennsylvania, Philadelphia, and colleagues wrote. Sickle cell trait (SCT), defined as one abnormal allele of the hemoglobin gene, is not considered a disease state because many carriers are asymptomatic, and therefore even less likely to be assessed for potential complications. “However, it is possible for people with SCT to experience sickling of red blood cells under severe hypoxia, dehydration, and hyperthermia. This condition can lead to severe medical complications for sickle cell carriers, including fetal loss, splenic infarction, exercise-related sudden death, and others,” they noted.
In a study published in JAMA Network Open, the researchers reviewed data from 63,334 deliveries in 50,560 women between Jan. 1, 2010, and Aug. 15, 2017, at four quaternary academic medical centers in Pennsylvania. Of these, 1,904 had SCT but not SCD, and 164 had SCD. The mean age of the women was 29.5 years, and approximately 56% were single at the time of delivery. A majority (87%) of the study population was Rhesus-factor positive, 47.0% were Black or African American, 33.7% were White, and 45.2% had ABO blood type O.
Risk factors for stillbirth used in the analysis included SCD, numbers of pain crises and blood transfusions before delivery, delivery episode (to represent parity), history of cesarean delivery, multiple gestation, age, marital status, race and ethnicity, ABO blood type, Rhesus factor, and year of delivery.
Overall, the prevalence of stillbirth in women with SCT was 1.1%, compared with 0.8% in the general study population, and was significantly associated with increased risk of stillbirth after controlling for multiple risk factors. The adjusted odds ratio was 8.94 for stillbirth risk in women with SCT, compared with women without SCT (P = .045), although the risk was greater among women with SCD, compared with those without SCD (aOR, 26.40).
“In addition, the stratified analysis found Black or African American patients with SCD to be at higher risk of stillbirth, compared with Black or African American patients without SCD (aOR, 3.59),” but no significant association was noted between stillbirth and SCT, the researchers wrote. Stillbirth rates were 1.1% in Black or African American women overall, 2.7% in those with SCD, and 1.0% in those with SCT. Overall, multiple gestation was associated with an increased risk of stillbirth (aOR, 4.68), while a history of cesarean delivery and being married at the time of delivery were associated with decreased risk (aOR, 0.44 and 0.72, respectively).
The lack of association between stillbirth and SCT in Black or African American patients supports some previous research, but contradicts other studies, the researchers wrote. “Ultimately, it may be impossible to disentangle the risks due to the disease and those due to disparities associated with the disease that have resulted from longstanding inequity and stigma,” they said. The findings also suggest that biological mechanisms of SCT may contribute to severe clinical complications, and therefore “invite a more critical examination of the assumption that SCT is not a disease state.”
The study findings were limited by several factors including the lack of assessment of SCT independent of other comorbidities, such as hypertension, preeclampsia, diabetes, and obesity, and by the use of billing codes that could misclassify patients, the researchers noted.
However, the results support some findings from previous studies of the potential health complications for pregnant SCT patients. The large study population highlights the need to identify women’s SCT status during obstetric care, and to provide both pregnancy guidance for SCT patients and systemic support of comprehensive care for SCD and SCT patients, they concluded.