viernes, 19 de junio de 2015




Recent NIOSH research has shed some light on the topic of the safety of N95 filtering facepiece respirators (FFR) use by pregnant workers. Women make up approximately one-half of the US work force. At any given time, about 10% of those female workers of child-bearing age (15–44 years of age) will be pregnant. Because many women are employed in occupations that require the use of protective facemasks, such as medical/surgical masks and FFR, NIOSH conducted research into the safety of FFR use while pregnant. The most frequently used FFR in the US is the N95 FFR (commonly referred to as “N95 mask”), but little information was previously available about the safety of N95 FFR use during pregnancy. Some individuals complain of difficulty breathing when wearing an N95 FFR or other protective facemasks, and many pregnant women find that they become somewhat shorter of breath as their pregnancy progresses, causing concern that use of N95 FFRs during pregnancy might make breathing even more difficult and possibly harm the woman and her fetus. Beyond the issue of use by pregnant working women on the job, the question also has implications for pregnant women outside the workplace. People sometimes use N95 FFRs as a matter of personal choice during infectious disease outbreaks, during environmental disasters that pollute the air, and even in more common recreational activities that may expose them to airborne allergens, such as gardening and woodworking.

NIOSH Research – Monitoring Oxygen Saturation and Transcutaneous Carbon Dioxide Levels of Pregnant Workers Who Wear Protective Facemasks

In these studies1,2 NIOSH researchers compared 22 healthy, non-smoking women who were in either their second or third trimesters of pregnancy with 22 healthy, non-smoking, non-pregnant women who were similar in age, height and weight. All of the women were experienced protective facemask users and were tested for one hour with and without wearing an N95 FFR while sitting, pedaling an exercise bicycle and standing.


There were no significant differences between the effects of wearing an N95 FFR on pregnant and non-pregnant women with respect to their heart rate and function, breathing rate, percentage of oxygen and carbon dioxide in their arteries, ear temperature, heart rate of the fetus, and blood pressure, as well as their impressions of any warmth or exertion associated with the respirator. The NIOSH study shows that the effects of wearing N95 FFRs are mild (average of one breath-per-minute decrease in the breathing rate, two beats-per-minute increase in heart rate, 1 – 7 mm Hg increase in diastolic blood pressure and 1- 2 mm increase in mean arterial pressure) and not different between pregnant and non-pregnant women. This is probably due to the fact that the filters of modern N95 FFR are able to be made thinner because they have electrically charged fibers that make them more efficient at trapping particles that are in the air, while at the same time being easier to breathe through. NIOSH researchers have also previously3 shown thatmedical/surgical masks have roughly the same impact as N95 FFR when worn for one hour, therefore it is likely that they too would be safe for use by pregnant women.
There are other reasons why some individuals may find it harder to breathe when wearing an N95 FFR or medical/surgical mask, such as feelings of anxiety or claustrophobia, an uncomfortable warmth in the region of the face that is covered by the N95 FFR, and a change from normal nose breathing to mouth breathing that may occur. Also, those who have lung problems such as poorly-controlled asthma or chronic bronchitis may find it difficult to breathe when wearing an N95 FFR. These tests were only carried out for one hour and more studies are needed to find out if there are any additional effects from wearing an N95 FFR for longer periods of time. Any pregnant worker who is required to wear a protective facemask at work should first check with a qualified health professional to determine if any contraindications to wearing it exist.

Summary of Key Findings

  • The effects of wearing an N95 FFR for one hour are similar for healthy pregnant and non-pregnant women.
  • Wearing an N95 FFR for one hour by healthy pregnant women does not have an effect on the fetal heart rate.
  • Similar effects would be expected with medical/surgical masks.

Raymond Roberge, MD, MPH; Jung-Hyun Kim, PhD; and Jeffrey B. Powell, MS
Dr. Roberge is a Research Medical Officer with the NIOSH National Personal Protective Technology Laboratory.
Dr. Kim is a Physical Scientist with the NIOSH National Personal Protective Technology Laboratory.
Mr. Powell is a Physical Scientist with the NIOSH National Personal Protective Technology Laboratory.

  1. Roberge RJ, Kim J-H, Powell JB. [2014] N95 respirator use during advanced pregnancy. American Journal of Infection Control 42: 1097-1100.
  2. Kim J-H, Roberge RJ, Powell JB. [2015]. Effect of External Airflow Resistive Load on Postural and Exercise-associated Cardiovascular and Pulmonary Responses in Pregnancy. BMC Pregnancy and Childbirth 2015;15:45-52.
  3. Roberge RJ, Kim J-H, Benson SM. [2012] Absence of consequential changes in physiological, thermal and subjective responses from wearing a surgical mask. Respiratory Physiology & Neurobiology 181: 29-35.

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