(183) Is preeclampsia with low sodium levels associated with preterm birth?

Preeclampsia (PEC) complicates 5-10% of all pregnancies. Preeclampsia and low sodium (PALS) has been previously reported; however, additional risks of low sodium levels in these patients is not well understood. We hypothesize PALS is associated with preterm birth (PTB).

Study Design:

Single center retrospective cohort of patients with PEC and a documented sodium level during delivery admission at Mount Sinai Hospital between 2013 and 2021. Demographic, obstetric, and neonatal outcomes of patients with and without low sodium, defined as sodium < 135 mmol/L, were compared. Primary outcome was PTB < 37 weeks. Secondary outcomes include gestational age at delivery, NICU admission, neonatal hyponatremia, mode of delivery, and indication for delivery. Primary and secondary outcomes were assessed using multivariable regression models, adjusting for history of preeclampsia in prior pregnancies, chronic hypertension, multiple gestation, aspirin use, history of PTB, and subtype of PEC.

Results:

Patients with PALS were more likely to be nulliparous (p=0.002), have a history of PEC (p=0.04), history of PTB (p=0.048), and history of prior cesarean delivery (CD) (p=0.01). The odds of PTB < 37 weeks among individuals with PALS is 1.76 times the odds among individuals with normal sodium levels (95% CI 1.09 – 2.83, Table 1). The odds of PTB < 34 weeks is 2.09 times the odds among individuals with low sodium levels compared to individuals with normal sodium levels (95% CI 1.17 – 3.75, Table 1). A trend towards earlier gestational age at delivery (36.9 vs 37.7 weeks, p=0.06) and higher rate of NICU admission (p=0.06) was noted in the hyponatremia group compared to the normal sodium group, although these associations were not statistically significant. Patients with PALS experienced higher rates of CD (p=0.03). Neonates born to patients with PALS experienced higher odds of hyponatremia (p=0.0009).

Conclusion:

Hyponatremia in patients with preeclampsia is associated with preterm birth < 37 weeks. These findings may prompt closer attention to sodium levels in the identification and management of patients with preeclampsia.