Advising on travel during pregnancy

First trimester

Although travel probably does not alter risk in women who are at increased risk of having an ectopic pregnancy or a miscarriage it will increase the difficulty (and cost) of management if either of them occurs. Women at increased risk of an ectopic pregnancy include those who have become pregnant after sterilisation or while using an intrauterine contraceptive device and those with previous ectopic pregnancy, tubal surgery, pelvic inflammatory disease, infertility, and documented tubal pathology.

A review noted that the miscarriage rate is 3-30% for women who experience vaginal bleeding in the first trimester.2 Prospective studies quote a miscarriage rate of only 3-5% if fetal heart activity is confirmed after bleeding.3 4

Second trimester

Pregnancy related complications, including miscarriage, are less common during the second trimester of pregnancy than in the first and the third trimester. Risks of an adverse pregnancy outcome are small and similar in nature to those described for the third trimester. The National Institute of Health and Clinical Excellence (NICE) schedule for antenatal care advises only one visit in the second trimester, after the 20-22 week anomaly ultrasound scan.5

Third trimester

Preterm delivery (spontaneous and iatrogenic, as a result of pregnancy complications) occurs in 7-12.3% of all pregnancies,6 7 depending on country of residence and ethnicity, but is often unpredictable. Women at increased risk of preterm delivery include those who have had a preterm birth, recurrent episodes of threatened preterm delivery, multiple pregnancy, or cervical trauma.

Miscarriage and preterm birth

A recent meta-analysis of nine studies, mainly retrospective cohort in design,8 reported that the risk of pregnancy loss was significantly greater in flight attendants than in controls (odds ratio 1.62, 95% confidence interval 1.29 to 2.04). Risk of preterm birth (less than 37 weeks) was also significantly higher in air passengers than in controls (1.44, 1.07 to 1.93), but not in flight attendants (1.37, 0.85 to 2.22). The authors note that studies were few in number and generally not of high methodological quality.

Venous thromboembolism (box 2)

Venous thromboembolism is 10 times more common in pregnant women than in matched non-pregnant women, and it complicates about one in a 1000 pregnancies.9 Inherent prothrombotic endothelial changes of pregnancy and relative obstruction to venous flow by the gravid uterus contribute to this. Travel may confer further risk of thrombosis because of immobility, low oxygen tension, and low humidity, which lead to venous stasis and dehydration.10

A recent cohort study reported that air travel was associated with a two to four times higher risk of a new thrombosis in non-pregnant people.11

Exposure to radiation

Exposure to radiation at any stage in pregnancy, but particularly during fetal organogenesis, is of concern. Exposure to cosmic radiation during flight is potentially greater than on the ground. Guidelines for diagnostic imaging in pregnancy from the American Congress of Obstetricians and Gynecologists (ACOG) conclude that there is no known increase in fetal malformations or miscarriage or effects on growth at levels less than 50 mSv.12 For comparison, the estimated cumulative background radiation per year in the United Kingdom is 2.2 mSv, a chest radiograph gives 0.1 mSv, and the radiation exposure from a 10 hour flight is estimated to be 0.05 mSv.13 The risk of adverse effects to the fetus from radiation during a single flight is negligible, but pregnant women who are frequent fliers, and airline staff who fly, may reach levels of exposure over the recommended maximum.

Low oxygen saturation

The partial pressure of oxygen in inspired air in aeroplane cabin environments maintained by cabin pressure is usually lower than it is at sea level. Physiological adaptations to this relative reduction in inspired oxygen include an increase in heart rate, increased blood pressure, and a decrease in transcutaneously measured arterial oxygen saturation.14 Fetal haemoglobin has a greater affinity for oxygen than does adult haemoglobin, 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 pre-existing cardiovascular problems, sickle cell disease, or severe anaemia (haemoglobin <80 g/L) may experience the effects of low arterial oxygen saturation.15 A routine haemoglobin check before travel is not currently recommended, but women with known anaemia should aim to optimise their haemoglobin before they travel, and those with severe anaemia should be advised to postpone air travel.

Travellers’ diarrhoea (box 3)

Travellers’ diarrhoea affects 10-60% of visitors to tropical and semi-tropical regions of the developing world.16 In pregnancy, decreased gastric activity and slowed intestinal transit may result in more severe dehydration and ketosis, which may increase the risk of premature labour.17

Malaria in pregnancy

Malaria in pregnancy carries substantial risks to mother and baby, particularly with Plasmodium falciparum infection. Pregnant women probably have a higher risk of being bitten by mosquitoes than non-pregnant women19; an increased risk of contracting malaria and dying from it20; a higher likelihood of malaria related hypoglycaemia21; and an increased risk of miscarriage, stillbirth, and premature labour if they develop malaria.22 Malaria prophylaxis is not 100% effective.10

Other infections

Hepatitis E is a faeco-oral hepatitis virus that is more likely to cause severe disease in pregnancy. There is currently no vaccine. The incidence of rubella is higher in many countries than in the United Kingdom; women who have not been vaccinated or infected in childhood are at increased risk of acquiring rubella. Acquiring HIV during pregnancy produces a high viral load, making mother to child transmission of HIV more likely. Many rarer infectious diseases ranging from typhoid to listeriosis pose a greater risk to the fetus, the mother, or both when acquired during pregnancy.

Women considering air travel

The Royal College of Obstetricians and Gynaecologists (RCOG) and the ACOG have both issued guidance on air travel in pregnancy. The ACOG states that healthy pregnant women with uncomplicated singleton pregnancies can fly safely up to 36 weeks’ gestation.15 Similarly, the RCOG guidelines state that there is no specific risk to pregnancy associated with commercial air travel.10 However, NICE suggests that pregnant women should be informed of the risk of venous thrombosis with long haul air travel, although it is unclear whether pregnancy confers an additional risk.5 The RCOG recommends prophylactic measures for pregnant women against venous thrombosis (box 2), including the use of correctly fitted compression stockings, which reduce the risk of thromboembolism in the general population,10 although no evidence exists on their effectiveness in pregnancy. Women with pre-existing cardiovascular problems, sickle cell disease, or severe anaemia should either not travel by air or they should consider supplemental oxygen if travel is unavoidable.

Women should be advised to wear a seatbelt while seated (whether travelling by aeroplane, car, or coach), strapped low under the abdomen, across the top of the thighs.10

Women consulting early in pregnancy

The location of the pregnancy should be confirmed ultrasonographically before travel in women who are at increased risk of miscarriage or ectopic pregnancy. In the presence of any abnormal symptoms (abdominal pain, bleeding) we advise women to defer travel until the pregnancy location and viability have been confirmed with ultrasound scan and symptoms have settled. If a woman is asymptomatic, many maternity units in the UK do not offer a routine first trimester ultrasound until 11-13 weeks’ gestation, and most early pregnancy units do not offer earlier routine scans solely for those considering travelling.

Women consulting after the first trimester

The ACOG considers the second trimester to be the best time to travel.15 Women who are at increased risk of preterm delivery should avoid long haul flights and consider the availability of maternity and neonatal care facilities.23 Facilities for managing the preterm infant may not be optimal or covered by insurance at the destination, and such facilities are not available on an aircraft. Other serious adverse events in pregnancy (such as major antepartum haemorrhage, severe pre-eclampsia, or cord prolapse) are not common but are difficult to predict; they may be life threatening, especially in the absence of trained personnel and adequate medical facilities. Airlines carry limited resuscitation facilities and often rely on the chance availability of a doctor. Only five of 17 international airlines questioned in 2004 carried delivery kits.24 A typical leading airline confirmed (2010) that although cabin crew undergo mandatory “pregnancy and emergency childbirth” training, the onboard medical kit contains a delivery pack, one 22 g cannula, one ampoule of ergometrine with oxytocin, and no crystalloid or colloid fluid.

Extended travel abroad and advice on travel insurance

Women should be encouraged to find out about the availability and quality of medical care at their chosen destination, including facilities for mother and baby. If they are travelling for long periods of time they should organise routine antenatal checks abroad. Women should travel with their handheld obstetric notes so that their medical details are readily available to any treating clinician, who can in turn update this information.

A survey of 138 women attending for ultrasound scan at 34 weeks’ gestation found that more than a third who had travelled during their pregnancy had done so without adequate insurance.25 Preterm babies may not be able to be repatriated for some months, and the costs may be substantial. Any woman considering travel while pregnant should take out insurance in the event of medical problems or delivery away from home. Many insurers will cover pregnant women only until 32 weeks’ gestation, and women should obtain agreement from their insurer in writing before travel. British women travelling in Europe should get a European Health Insurance Card (EHIC) and carry it at all times; it shows that they are eligible for free or reduced cost emergency medical care but does not replace travel insurance and will not cover the cost of repatriation.

Travel to a malaria endemic country

Risks of acquiring malaria vary considerably. In many parts of sub-Saharan Africa in particular, the average person may get malaria several times a year. The RCOG advises against travel to malaria endemic zones during pregnancy.26 If travel is unavoidable, encourage women to take chemoprophylaxis, which—although not 100% effective—carries a low risk to the fetus, especially in the second and third trimesters, compared with the much higher risks to the pregnancy associated with malarial infection if prophylaxis is not taken. The choice of chemoprophylaxis depends on specific incidence of malaria at the destination and level of drug resistance to P falciparum. We advise seeking specialist input for women in the first trimester because of the small theoretical potential for teratogenicity from antimalarial drugs that must be weighed against the substantial risk of acquiring malaria. To avoid bites pregnant women should always sleep under treated mosquito nets in a malaria endemic area and wear long clothing after dark. A low index of suspicion for a diagnosis of malaria in women who have travelled to endemic areas is vital, and given the high risk to the pregnancy urgent specialist advice is recommended for treatment.

Are travel vaccinations safe in pregnancy?

The risks of vaccination during pregnancy on the developing fetus are unclear. The Centers for Disease Control and Prevention state that there is no evidence of risk from vaccinating pregnant women with inactivated virus, bacterial vaccines, or toxoids.27 It is advised that pregnant women avoid live vaccines, such as yellow fever, because of the small risk of contracting a disease that is potentially harmful to the fetus.28 For yellow fever a letter from a doctor or travel centre stating why vaccination has not been given reduces the risk of pregnant women being turned away or vaccinated on arrival. Inactivated vaccines are generally considered safe, although those associated with febrile reactions (such as oral typhoid) are generally not advised unless the risk is high, because they have been linked with miscarriage.27 Women should seek up to date information from an appropriate travel clinic about vaccination and should be encouraged to avoid disease endemic areas (table 2⇓).