Standardized policies regarding routine national and international commercial travel of pregnant passengers are nonexistent (3). Civil air company policies, however, do take into account the length of the pregnancy. The more advanced the gestation, the more likely rupture of membranes, labor, or delivery will occur. Predictors for many pregnancy-related events are not always readily evident. Fifty percent of the pregnancies that result in preterm delivery have no identifiable risk factors (4). What are the implications? Diversion for even a commuter flight can be expected to take 30 to 45 minutes depending on meteorologic conditions and air traffic. Responding commercial airlines in a survey by Breahtnach et al. reported that only 70% trained aircrew in delivery and fewer than 30% had a full delivery kit (3). Therefore, a conservative approach with some flexibility is generally employed. Many airline medical departments allow pregnant travelers to fly at their discretion to 36 weeks estimated gestational age for domestic flights and 35 weeks for international, or specifically, transcontinental or transoceanic flights (5). Exceeding airline restrictions generally requires a medical provider statement verifying that labor is not imminent and no underlying complications exist.

Women with complicated pregnancies may encounter other risks with air travel. Absolute contraindications to air travel include ruptured membranes, bleeding during pregnancy, diagnosed ectopic pregnancy, and severe preeclampsia. First trimester bleeding can represent an undiagnosed ectopic pregnancy or threatened/incomplete abortion. Fifteen to 20% of clinically recognized pregnancies end in spontaneous abortion. Second and third trimester bleeding can represent labor, incompetent cervix, abruption, or placenta previa (6). Pregnancies complicated by multiple gestations, a history of preterm labor (PTL), or existing uterine irritability are predisposed to early delivery. Severe anemia affects oxygen delivery to the placenta and should be corrected before flight or minimally necessitates in-flight oxygen supplementation. Oxygen therapy should also be supplied for conditions that potentially compromise placental reserve such as intrauterine growth restriction, postmaturity, and preeclampsia.

The risk with air travel in pregnancy may be minimal in comparison to the environmental risk, such as endemic malaria, that may be encountered in the ultimate destination. The best policy is to consider all aspects of the proposed journey including lodging, activities, food, and medical support, and to mitigate risk that each of these elements poses by establishing sound prenatal care. Pretravel prenatal care typically includes ultrasonography, assessment of immune status to various infections, the need for immunization, malaria prophylaxis, and creation of a prenatal record. Ultrasonography facilitates more precise dating of the pregnancy and helps confirm suspected multifetal gestation and ectopic pregnancy. Non contraindicated immunizations can be administered. Typically, live viral vaccinations such
as mumps, rubella, oral polio, varicella, and yellow fever are avoided in pregnancy. Prescriptive medications, including malaria chemoprophylaxis and other stand-by therapies such as antiemetics and antidiarrheals should be considered (7). The prenatal record should be carried together with the passport, visa, and immunization records.

Pregnant aircrew have distinct responsibilities and required activities in the performance of their flight duties. The changing balance, flexibility, mobility, and body habitus in pregnancy become evident in the second trimester and may interfere with the ability to safely pilot or assist passengers during an emergent egress. Therefore, commercial aircrew is generally restricted from duties after 28 weeks or completion of the second trimester (8). Although pregnancy is not disqualifying in general aviation, the aircrew must be made aware of the impact flying has on the third trimester such as cockpit ergonomics and placental reserve. Placental maturation continues throughout pregnancy. Maturation beyond 34 to 36 weeks is affiliated with several processes including microcalcification deposition that affect oxygen delivery to the fetus and ultimately lower fetal respiratory reserve. This lowered reserve may not pose a problem in the uncomplicated pregnancy in an oxygen tension encountered at 8,000 ft (the commercial cabin), but may become problematic for the nonacclimated fetus in an oxygen tension encountered at 14,000 ft (general aviation, nonpressurized cabin).

Women who fly high-performance military aircraft or are engaged in aerial aerobatics will experience high levels of accelerative force (G force). Egress through an ejection seat will result in higher accelerative force. These forces can be sudden, unexpected, and violent and may pose an unacceptable maternal or fetal risk in the gravid aviator. Resultant outcomes would be dependent on gestational age. Significant first trimester insults are likely limited to a fetal loss with no immediate bleeding and would not result in any additional maternal morbidity beyond the nongravid female. Therefore, the gravid female aviator would be just as successful piloting the aircraft or surviving the egress. Significant second or third trimester exposure poses the additional risk of uterine rupture. Twenty percent of cardiac output flows to the uterus by 30 weeks. Therefore, rupture of the uterus or placental abruption would likely result in both fetal loss and profound maternal morbidity or mortality. In this scenario, it is unlikely that she would be able to pilot the aircraft (aircraft loss) or survive the ejection. There are no available studies that address these issues, and pregnant aviators should seek counsel from both their obstetrician and their flight surgeon to determine the point in the pregnancy where temporary grounding would be appropriate. Informed consent must be universally applied to performance aircraft or platforms with ejection seats.

The unique physiology of pregnancy is impacted by the flight environment (Table 22-1). In general, these considerations apply to the gravid aircrew/frequent flyer or the infrequent traveler. Aeromedical providers must have familiarity with system-specific maternal physiologic changes of pregnancy as well as fetal physiology in order to perform appropriate consultation and policy promulgation for the gravid female or provide aeromedical evacuation (AE) en route care for the pregnant (or newly postpartum) patient. As an example, an asymptomatic 31-year-old passenger at 30 weeks gestation with focal findings of a systolic ejection murmur with an S₃ gallop and lower dependent edema is likely normal and cleared to schedule her commuter flight as opposed to same findings and suspicion of heart failure in a nongravid female of the same age.

Perinatal regionalization, emphasized strongly beginning in the 1990s, has been associated with improved outcome for very low birth weight infants and for women with complications requiring intensive services. This phenomenon involves stabilization of the mother, intrauterine transfer, and the optimum delivery at a medical center that has the volume to sustain costly technology and specialized personnel (13). Generally, the best and most efficient fetal transport mechanism, delivering oxygen and nutrition to the fetus, remains the gravid mother. Clinical circumstances may dictate it is safer to transport medical personnel to the patient than transport an unstable patient in an unstable environment. General contraindications to maternal air transport include maternal instability, a rapidly deteriorating fetus, imminent delivery, lack of experienced (en route) medical
attendants, and hazardous flight conditions (meteorologic). This assessment of transport versus local care is best left to the accepting or aeromedically validating perinatal team. As with all medical evacuation, arrangements for transfer should be made before the transport. Standing agreements with referral hospitals should be established to provide sufficient guidance for transport and provide communication consistency (14).

The transport team should be familiar with the aviation environment and skilled in perinatal care that includes the ability to perform a vaginal delivery. When possible, the evacuating platform should be suited to support equipment that may be needed during transport. Standard equipment includes a delivery kit, uterotonics, oxygen, intravenous fluids, an infant warmer, and maternal and fetal stabilization equipment. Pharmacologic agents such as tocolytics, oxytocin, calcium gluconate (magnesium toxicity), antihypertensives, and antiemetics are useful while handling the more common complications during transport (Table 22-2). Preflight assessment and preparation typically include a cervical check [except in suspected placenta previa or preterm premature rupture of membranes (PPROM) without labor] and intravenous access and adequate airway, if indicated. Transport in a left lateral recumbent position displaces the gravid uterus off the vena cava and thereby increases maternal venous return and subsequent cardiac output and uterine perfusion. Advanced cardiac life support considerations are the same as for the nongravid female. The fetal heart rate can be assessed with a handheld Doppler with digital display (14). Oxygen supplementation should be used liberally as it improves fetal cerebral cortical oxygen tension (15). Planning the AE, including the decision to use fixed wing or rotary aircraft, depends on a myriad of factors including available assets, meteorologic conditions, geography/terrain, airfield support, landing areas, and the distance to the nearest appropriate medical facility (14).