Pregnancy and Flying
by
Dr. P Gopal
Sc 'E'
IAM, IAF

INTRODUCTION
Women have been involved in aviation since 1784 when Madame Elizabeth Thible went aloft in a Montgolfist balloon over Lyon, France (1). Generally speaking when women first took to the air in the pioneer days of flight, their efforts frequently met with scorn and ridicule. Flying was a male preserve and many were determined to keep it so. The honour of being the first woman in the world to earn a pilot's licence belongs to Mme Elise de Laroche. In 1930 Amy John flew alone from England to Australia, and two years later Amelia Earhart crossed the Atlantic from America.

The militaries of the world did not permit women to undergo pilot training until mid seventies. But women continued flying in civil aviation circles.

PREGNANCY AND FLYING
The very birth of aviation medicine was in the study of physiological effects of altitude. However, relatively little is found regarding the effects of altitudes of modern transport aircraft i.e. 5000 to 7000 ft. Also large number of women, in the early stages of pregnancy spend winter vacation in resorts with altitudes between 6000 and 7000 ft. A 10-day vacation at these altitudes would expose such women to the same degree of hypoxia as that experienced by a hostess with an 80-hour monthly flight duty time. No consideration is taken of periods spent by vacationers at high altitudes.

At normal atmospheric pressure, the differential PO2 between maternal brachial arterial blood and foetal umbilical venous blood is 58.8 mm Hg. At an altitude of 8000 ft. such a differential pressure would lead to a fatally low PO2 of only 5.6 mm Hg (1). But this is countered by two factors. Foetal oxygen dissociation curve lies to the left of maternal curve. Under defined conditions of temperature and pH or PCO2, at a given partial pressure, the oxygen saturation of foetal blood is greater than that of maternal blood. In human foetus the oxygen carrying capacity of foetal Hb is 5ml/100ml more than that of maternal blood, Further more, as the maternal blood passes through the inter - villous space, it receives CO2 and s