Keywords
pregnancy - travel - fetus - airplane
Most commercial airlines allow pregnant women to fly up to 36 weeks of gestation.[1] Some restrict pregnant women from international flights earlier in gestation and
some require documentation of gestational age. For specific airline requirements,
women should check with the individual carrier.[1] Recent cohort studies suggest no increase in adverse pregnancy outcomes for occasional
air travelers for low-risk patients.[2]
[3] Available information suggest that noise, vibration, and cosmic radiation present
a small risk for the pregnant air traveler.[4] Both the National Council on Radiation Protection and Measurements and the International
Commission on Radiological Protection recommend a maximum annual radiation exposure
limit of 1 millisievert (mSv) (100 rem) for members of the general public and 1 mSv
over the course of a 40-week pregnancy.[5] Even the longest available intercontinental flights will expose passengers to no
more than 15% of this limit[5]; therefore, it is unlikely that the occasional traveler will exceed current exposure
limits during pregnancy. However, aircrew or frequent flyers may exceed these limits.
There is a paucity of information regarding risks of air travel in pregnancy, most
of it stemming from fairly old series.[3] While one study deduced that “such low level of hypoxia as that which in an aircraft
has little effect on the fetus,” another author argued that the “changing mechanics
of pregnancy lend credence to the argument that pregnant stewardesses should not fly.”[6]
[7]
The goal of the study was to assess the possible effect of transatlantic flights on
the condition of the third-trimester fetus.
Materials and Methods
One hundred and twelve patients were recruited into the study between January 2005
and June 2016. All underwent a transatlantic flight in the third trimester of pregnancy.
All patients were between 34 and 37 weeks of gestation. All underwent nonstress test
(NST) before and within 12 hours after the transatlantic flight, and 24 hours later.
Patients were asked to report changes in fetal movements (FMs), if any, during takeoff,
flight itself, and landing.
Statistical evaluation was made using SPSS for Windows V 15.0 (SPSS Inc.). Data were
shown as frequency (percentage) or mean ± standard deviation.
Results
The time of flight varied from 8 to 15 hours; average flight time was 9 ± 3.8 hours.
Ninety-eight patients were the passengers of first or business class, and the rest
were of economy class. Patients' ages varied from 22 to 39 years, average being 26 ± 5.2
years. NST parameters are reflected in [Table 1].
Table 1
|
NST before flight
|
12 h after flight
|
24 h after flight
|
|
Reactive
|
93%
|
73%a
|
94%
|
|
Presence of visible decelerations
|
6%
|
14%
|
4%
|
Abbreviation: NST, nonstress test.
Increased FM during takeoff was reported by 17 patients (15%), no change in FM by
62 (35%), decreased FM by 4 (3.6%). During flight itself, increased FM was reported
by 6 pregnant passengers (5.4%), no change in FM by 70 (63%), decreased FM by 8 (7%).
Discussion
Magann et al[8] conducted a literature review on air travel and pregnancy outcome among other issues
(e.g., cosmic radiation, risk of acquiring respiratory disease, possibility of obstetrical
emergencies) and addressed one of the possible risks to the fetus, aircraft noise.
A review of perinatal effects of noise emphasizes the lack of properly controlled
studies to draw meaningful conclusions about the effects or lack of effects of noise
on birth defects and perinatal outcomes.[9] The World Health Organization has labeled noise of greater than 85 dB as potentially
hazardous.[10] In both military and civilian aircraft, the greatest noise exposure is during takeoff
and landing. Indeed, Freeman et al[3] observed increased fetal heart rate during takeoff and landing. The majority of
our patients reported increased FMs at these times. It remains unclear whether these
changes are caused by aircraft noise, maternal anxiety, or a combination of both.
These fetal responses are very similar to the ones experienced by fetuses exposed
to cell phone noise. Frequent acoustic stimulation by cell phones and beepers was
accompanied by a startle response manifested by head turning toward the source of
the sound, increased swallowing, and frequent eye blinking. Startle responses were
observed in all fetuses of the study group and only in 12% of the fetuses in the control
group. Besides causing startle response, acoustic stimulations were associated with
changes in behavioral states, most notable, from quiet and active sleep into an awakened
state.[11]
[12]
The partial pressure of oxygen in inspired air in airplane cabin environments maintained
by cabin pressure is usually lower than that at sea level. Physiological adaptations
to this relative reduction in inspired oxygen include an increase in heart rate, increase
in blood pressure, and decrease in transcutaneously measured arterial oxygen saturation.
Fetal hemoglobin has a greater affinity for oxygen than adult hemoglobin, and the
fetus is able to maintain a higher oxygen saturation in this environment, which protects
it during routine flight conditions. Most healthy pregnant women will have no adverse
effects, but those with preexisting cardiovascular problems, sickle cell disease,
or anemia[13] may experience complications.
Our study demonstrated significant changes in FHR parameters immediately after the
transatlantic flight. It manifested in the increased rate of nonreactive NSTs and
more frequent appearances of variable decelerations. The strength of the paper is
its prospective nature and the fact that all patients were flying the same or similar
distances. In most previous studies, data from intercontinental and domestic flights
were analyzed together, thus causing confusion. In spite of the fact that on long
commercial flights, traveling at 39,000 to 41,000 ft., cabin pressure is maintained
at the equivalent of an altitude pressure of 8,000 ft., whereas at 32,000 ft. (for
shorter flights), cabin pressure is set at an equivalent of 6,000 ft.[14] The conditions at a cabin pressure of 8,000 ft. will create a more hypoxic environment
than those at 6,000 ft. At 6,000 ft., oxygen consumption in pregnant women is 13%
(L/minute) lower than that at sea level in comparison with nonpregnant women for whom
the decrease is only 3% lower.[2] The limitations of the study are relatively small sample size and the subjective
nature of FM assessment based on patients' diaries. Our study demonstrated that although
transatlantic flights may cause only temporary changes in fetal behavior and appears
safe for the fetus, these conclusions are limited to third-trimester fetuses.
