Abnormal Calcium Levels are Associated With Worse Maternal and Fetal Outcomes; Results From an Exploratory Study

Abstract

Context: Precise estimates of the incidence of hyper- and hypocalcemia in pregnancy are unknown. Abnormal calcium levels have been associated with unfavorable pregnancy-related outcomes.

Objective: Determine frequency of hypercalcemia and hypocalcemia in pregnancy when tested and their associations with maternal and fetal outcomes.

Design: Exploratory retrospective cohort study.

Setting: Single tertiary care maternity unit.

Patients: Pregnant women with expected delivery date between 2017 and 2019 and a second additional cohort of pregnant women with hypercalcemia between 2014 and 2016 and 2020 and 2021.

Interventions: Observational.

Main outcomes measured: (1) Incidence of hyper- and hypocalcemia when calcium tested; (2) maternal outcomes: incidence of preterm delivery, emergency cesarean section, and blood loss during delivery; and (3) fetal outcomes: fetal loss (miscarriage/stillbirth), neonatal intensive care unit admission, and fetal birth weight (for term deliveries).

Results: Total number of gestations and livebirths recorded were 33 118 and 20 969, respectively, with median [interquartile range] age of 30.1 [25.6-34.3] years. A total of 15.7% (n = 5197) of all gestations had albumin-adjusted calcium tested, and incidence of hypercalcemia and hypocalcemia when tested was 0.8% (n = 42) and 9.5% (n = 495), respectively. Both hypercalcemia (including additional cohort n = 89) and hypocalcemia were associated with increased incidence of preterm delivery (P < .001), emergency cesarean section (P < .001 and .019), blood loss (P < .001), and neonatal intensive care unit admission (P < .001). A total of 27% in the hypercalcemic group had an established diagnosis of primary hyperparathyroidism.

Conclusions: Abnormal calcium levels during pregnancy are common and associated with worse pregnancy-related outcomes, which raises the possible need for routine calcium testing. Prospective studies to confirm the incidence, etiology, and effects of abnormal calcium in pregnancy are recommended.

Keywords: hypercalcemia; hypocalcemia; pregnancy.