Is Maternal Core Temperature Elevated Beyond a Critical Threshold During Exercise in Pregnancy?

Learning Objectives and CME/Disclosure Information

This activity is intended for healthcare providers delivering care to women and their families.

After completing this activity, the participant should be better able to:

1. State potential risks associated with elevated maternal core temperature
2. Discuss the results obtained from the meta-analysis by Ravanelli et al. regarding maximal core temperatures reached during pregnancy by women participating in exercise, hot tub and sauna activities

Estimated time to complete activity: 0.25 hours

Faculty:

Susan J. Gross, MD, FRCSC, FACOG, FACMG
President and CEO, The ObG Project

Disclosure of Conflicts of Interest

Postgraduate Institute for Medicine (PIM) requires instructors, planners, managers and other individuals who are in a position to control the content of this activity to disclose any real or apparent conflict of interest (COI) they may have as related to the content of this activity. All identified COI are thoroughly vetted and resolved according to PIM policy. PIM is committed to providing its learners with high quality CME activities and related materials that promote improvements or quality in healthcare and not a specific proprietary business interest of a commercial interest.

Faculty: Susan J. Gross, MD, receives consulting fees from Cradle Genomics, and has financial interest in The ObG Project, Inc.

Planners and Managers: The PIM planners and managers, Trace Hutchison, PharmD, Samantha Mattiucci, PharmD, CHCP, Judi Smelker-Mitchek, MBA, MSN, RN, and Jan Schultz, MSN, RN, CHCP have nothing to disclose.

Method of Participation and Request for Credit

Fees for participating and receiving CME credit for this activity are as posted on The ObG Project website. During the period from April 8 2018 through April 8 2021, participants must read the learning objectives and faculty disclosures and study the educational activity.

If you wish to receive acknowledgment for completing this activity, please complete the post-test and evaluation. Upon registering and successfully completing the post-test with a score of 100% and the activity evaluation, your certificate will be made available immediately.

For Pharmacists: Upon successfully completing the post-test with a score of 100% and the activity evaluation form, transcript information will be sent to the NABP CPE Monitor Service within 4 weeks.

Joint Accreditation Statement

In support of improving patient care, this activity has been planned and implemented by the Postgraduate Institute for Medicine and The ObG Project. Postgraduate Institute for Medicine is jointly accredited by the Accreditation Council for Continuing Medical Education (ACCME), the Accreditation Council for Pharmacy Education (ACPE), and the American Nurses Credentialing Center (ANCC), to provide continuing education for the healthcare team.

Physician Continuing Medical Education

Postgraduate Institute for Medicine designates this enduring material for a maximum of 0.25 AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Continuing Nursing Education

The maximum number of hours awarded for this Continuing Nursing Education activity is 0.2 contact hours.

Read Disclaimer & Fine Print

BACKGROUND AND PURPOSE:

Animal model evidence and retrospective studies in humans have demonstrated increased risk of fetal malformations in the setting of severe hyperthermia (primarily related to fever)
Maternal core temperature exceeding 39.0°C (or an elevation of ~1.5°C to 2.0°C from baseline) has been suggested as the critical threshold to avoid additional risk of birth defects, especially neural tube defects
ACOG, RANZCOG and RCOG discourage prenatal use of hot tubs and saunas and to avoid heat and humidity during pregnancy
Exercise during pregnancy is recommended, however
- Concern that more intensive exercise may result in increased maternal core temperature
- Alternatively, thermoregulation may keep core temperature below a critical level
Ravanelli et al. (British Journal of Sports Medicine, 2018) examined whether exercise and passive heat stress can negatively impact pregnancy by elevating core temperature to a critical level beyond 39.0°C

METHODS:

Systematic review and meta-analysis
Studies were included that reported the core temperature response of pregnant women
The critical core temperature for teratogenicity risk was defined as ≥39.0°C
The core temperature was measured during any period of gestation in response to exercise or passive heat stress

RESULTS:

Data was pooled from 12 studies, for a total of 347 subjects
There were no reports of any core temperature exceeding the recommended maternal threshold of 39.0°C
- Overall, 38.9°C was the highest reported individual core temperature
The highest mean end-trial core temperature was
- 38.3°C (95% CI 37.7°C to 38.9°C) for land-based exercise
- 37.5°C (95% CI 37.3°C to 37.7°C) for water immersion exercise
- 36.9°C (95% CI 36.8°C to 37.0°C) for hot water bathing
- 37.6°C (95% CI 37.5°C to 37.7°C) for sauna exposure

CONCLUSION:

This study suggests that pregnant women at any gestational stage can safely engage in
- Exercise for up to 35 min at 80%–90% of their maximum heart rate in 25°C temperature and 45% relative humidity
- Water immersion (≤33.4°C) exercise for up to 45 min
- Sitting in hot baths (40°C) or hot/dry saunas (70°C; 15% relative humidity) for up to 20 min

Learn More – Primary Sources:

Heat stress and fetal risk. Environmental limits for exercise and passive heat stress during pregnancy: a systematic review with best evidence synthesis

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Is Maternal Core Temperature Elevated Beyond a Critical Threshold During Exercise in Pregnancy?