Am J Perinatol 2022; 39(16): 1745-1749
DOI: 10.1055/a-1745-3262
Short Communication

Changing Tocolytic Exposures among Neonatal Intensive Care Unit Admitted Preterm Infants

Meghan L. Jarman
1   Department of Pediatrics, San Antonio Uniformed Services Health Education Consortium, San Antonio, Texas
Monica M. Bennett
2   Research Analytics and Development Cores, Baylor Scott and White Research Institute, Dallas, Texas
Judette M. Louis
3   Department of Obstetrics and Gynecology, University of South Florida, Tampa, Florida
Reese H. Clark
4   MEDNAX Center for Research Education, Quality, and Safety, Sunrise, Florida
Veeral N. Tolia
5   Department of Pediatrics, Baylor University Medical Center, Dallas, Texas
6   Pediatrix Medical Group, Dallas, Texas
1   Department of Pediatrics, San Antonio Uniformed Services Health Education Consortium, San Antonio, Texas
4   MEDNAX Center for Research Education, Quality, and Safety, Sunrise, Florida
7   Pediatrix Medical Group of San Antonio, San Antonio, Texas
8   Department of Pediatrics, Baylor College of Medicine, San Antonio, Texas
9   Pediatrix and Obstetrix Specialists of Houston, Houston, Texas
10   Department of Neonatology, The Woman's Hospital of Texas, Houston, Texas
› Author Affiliations
Funding None.


Objective Since 2010, the American College of Obstetrics and Gynecology have released three committee opinions to recommend and reaffirm the utility of magnesium sulfate for neuroprotection and later for tocolysis to achieve antenatal steroid course completion in preterm labor. We sought to determine changes in antenatal magnesium sulfate exposure and other tocolytic agents for pregnancies resulting in neonatal intensive care unit (NICU)-admitted preterm infants.

Study Design Using the Pediatrix Clinical Data Warehouse, we evaluated all inborn infants delivered between 22 and 33 weeks' gestation and admitted to the intensive care units from 2009 to 2018. We classified patients based on antenatal exposure to tocolytic medications: calcium channel blockers (nifedipine and amlodipine), betamimetics (terbutaline, theophylline, and ritodrine), prostaglandin inhibitors (indomethacin), and magnesium sulfate.

Results A total of 229,781 patients met inclusion criteria. During the study period, magnesium sulfate exposure increased from 27.6 to 57.7% of births while betamimetic exposure decreased from 10.2 to 5.2%. Increasing magnesium sulfate exposure over time was seen at all gestational ages examined and magnesium exposure was most common between 23 and 31 weeks' gestation. By 2017 to 2018, 70.5% of 24 to 29 weeks' gestation NICU infants received exposure to at least one tocolytic agent while this remained at 53.7% of 32 to 33 weeks' NICU admitted infants. Antenatal steroid exposure increased from 74.8 to 87.4% during the study period.

Conclusion For NICU-admitted preterm infants, prenatal exposure patterns to tocolytic agents has shifted since 2009 with prenatal magnesium sulfate exposure increasing significantly. Antenatal steroid exposure has risen concurrently. Exposure to tocolytic agents is the highest among preterm infants born between 24 and 29 weeks' gestation.

Key Points

  • Exposure to magnesium sulfate significantly increased from 2009 to 2018 for NICU admitted infants.

  • Concurrently, the use of other tocolytics decreased significantly.

  • The use of antenatal steroids has been rising over time.

Prior Presentations or Abstracts

This study was accepted to the 2020 Pediatric Academic Societies Meeting; however, presentation cancelled due to novel coronavirus disease 2019 (COVID-19).

Publication History

Received: 30 May 2021

Accepted: 17 January 2022

Accepted Manuscript online:
19 January 2022

Article published online:
17 February 2022

© 2022. Thieme. All rights reserved.

Thieme Medical Publishers, Inc.
333 Seventh Avenue, 18th Floor, New York, NY 10001, USA