Quick take: Air travel increases the risk of dehydration and deep vein thrombosis in the pregnant woman. Other risks have not been established.
Air travel entails prolonged immobilization, exposure to reduced atmospheric pressure, to very dry air, and to an increase in cosmic radiations. Of these, exposure to ionizing radiations is least likely to be problematic because such exposure does not involve large radiation dose levels (see X ray #1221) (6). Some commentators were not convinced that air travel does not pose a radiation risk for pregnancy (7,8). Flying through solar particle events can entail exposure to additional radiation (25). A 2008 Canadian study estimated that the dose to the fetus would exceed a recommended fetal dose limit of 1 mSv after 10 round trips on commercial flights between Toronto and Frankfurt (17). For details on how individual patients can estimate their radiation exposure during air travel, see ref 13. The Federal Aviation Administration offers a calculator for estimating radiation doses for specific flights (26) and a discussion of workplans for pregnant crew members (31).
The cabin pressure in commercial jets is the equivalent of an altitude of 5000-8000 feet. Symptoms of hypoxia #3068 are seen at altitudes of above 10,000 feet. It is generally recommended that pregnant women avoid flying above 10,000 feet in an unpressurized plane. Most airlines allow pregnant women to fly up to 36 weeks of gestation (30). For international travel, the cutoff can be 35 weeks gestation (9,30), but some airlines have no restrictions on pregnant travelers and no trained personnel to help with obstetric emergencies (15). Women with an increased risk of preterm delivery, placental abnormalities, pregnancy induced hypertension, poorly controlled diabetes, or sickle cell trait are discouraged from traveling by air at any time during pregnancy (9,18,20).
The dryness of the air coupled with the usual increase in minute ventilation associated with pregnancy will predispose pregnant women to dehydration; therefore, increased fluid intake during air travel is recommended. Prolonged immobilization can exacerbate the thrombotic tendencies of pregnancy (4,24). Preventative measures include the use of support stockings and periodic movement of the lower extremities (9,19,32).
Whether reduced atmospheric pressure is associated with decreased oxygen delivery to the fetus has been addressed by a study in which continuous fetal heart rate monitoring was used during air transport of women with obstetric complications. No late decelerations were seen, leading the authors to conclude that fetal hypoxia was not present (1). Another study of ten healthy pregnant women in the third trimester found no abnormalities of fetal heart rate tracings during jet air travel in spite of decreases in maternal transcutaneous pO2 (2). Two 2012 reviews of long distance air travel in the second and third trimesters of pregnancy found no adverse maternal or fetal effects (22,23). Alterations in fetal oxygenation would not be expected under these conditions in view of the shift of the fetal oxyhemoglobin dissociation curve to the left of the adult curve. This shift promotes maximal fetal hemoglobin saturation unless maternal pO2 becomes lower than about 60 torr. Some commentators concluded in 1998 that any developmental risk associated with the hypobaria of air travel is apparently small but worthy of additional investigation (11,12).
In a 1990 study, one group reported finding an increased risk (relative risk=1.9) of first trimester spontaneous abortions among flight attendants (10), but these findings have not been duplicated by others. A 2015 study did not find the incidence of miscarriage was higher among flight attendants than among school teachers (21). Another study of 145 former flight attendants reported a higher incidence of miscarriage compared with a general population value, and 5 of 97 women reported births with congenital defects. The authors did not address the selective influence that reproductive history might have had on the women who chose to participate in their study. Miscarriages among flight attendants unrelated to second-hand smoke exposure on airplanes was considered elevated at 26% compared to a general population rate of 17.1% (29). This comparison to a general population rate may not be informative.
A retrospective analysis of possible effects of air travel on pregnancy was undertaken by Saudi investigators by comparing the outcomes of pregnancy in 546 women who traveled at least once during pregnancy and a control group of 447 women who did not travel by air (14). The authors noted that the air travelers had uncommonly long durations and frequency of air travel. They attempted to adjust for variables that would differ between the lives of frequent travelers and non-travelers. They found an increased risk of preterm birth and lower birth weight in travelers. There were no thromboembolic events complicating any pregnancies. A second group that identified 222 women who had flown at least once during pregnancy and delivered after 20 weeks gestation did not find air travel associated with increased risk of reduced gestational age or low birth weight (16). Birth weight and gestational age were not altered in a cohort of 41,000 women who traveled by air during pregnancy (33).
In Western Australia, women at immediate risk of preterm delivery are routinely transferred over long distances by air to a perinatal center in Perth (22). The record of 500 such pregnancies collected over 30 years showed that no women went into labor during the flight. Ambient altitude of greater than 14,000 feet or cabin altitude above sea level were associated with a delay in time from landing to delivery in women not in spontaneous preterm labor. US and international regulations regarding pregnant military aviators were discussed in a 2010 review (20). This review included discussion of removal from active flight status based on concerns about of gravitational forces, hypobaric hypoxia, cosmic radiation, and ejection seats.
Pregnant women may be at higher risk than nonpregnant individuals for venous thromboembolism (VTE) with air travel; air travel presents an increased risk for thromboembolism in travelers whether pregnant or not (27). Pregnant women are considered to have a 5- to 10-fold increased risk of thromboembolism when compared to nonpregnant women and a risk increased 20- to 80-fold during the postpartum period (27,32).
There is a case report of placental separation in a woman at 14 weeks gestation attributed to turbulence, despite the use of a seat belt #4139 (28). The American College of Obstetricians and Gynecologists recommended in 2009 that pregnant women wear seat belts on airplanes with the belt low across the hips between the abdomen and pelvis (18,30).
Menstrual dysfunction, including menorrhagia, dysmenorrhea, and prolonged follicular phase of the menstrual cycle have been reported in flight crew members (5). Whether these effects are due to stress #1989, from the physical exertion, time zone changes, or an actual environmental effect of air travel is not known.
A report on male mink showed an impairment of sperm quality and a delay in sexual maturation in young animals transported in utero from America to Finland (3). While the air travel might have adversely affected intrauterine development of these mink, other factors may have been operative. For example, rearing by mothers that had been subjected to the handling and other rigors of the transport might have caused alterations in neonatal development.
We have not located studies on possible lactation effects of air travel.
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