The Boston woman was in her 38th week of pregnancy when a close family member died in New York City.

She asked her obstetrician, Dr. William Barth Jr. of Massachusetts General Hospital, if traveling to the funeral was out of the question.

No, it's fine to make a quick plane trip, the doctor remembers telling his patient after he examined her. "I thought the likelihood of labor was low, and this was an important occasion," he said.

Indeed, occasional air travel is safe for healthy pregnant women, according to a new committee opinion issued by the American College of Obstetricians and Gynecologists.

That holds true even in the last month of pregnancy, although most doctors generally prefer that women stop air travel around 36 weeks in case they go into early labor, said Barth, chairman of ACOG's Committee on Obstetric Practice.

"Exercise normal precautions" by drinking lots of water, getting up and walking, wearing support stockings and keeping your seat belt fastened while seated, he advises soon-to-be moms who choose to fly. Because pregnant women are at increased risk of blood clots, these measures are "even more important," Barth said.

If your stomach has been on a roll during pregnancy, consider taking an anti-nausea pill before getting on a plane. Also, avoid consuming foods or drinks that can cause gas because gas will expand in your stomach at high altitudes.

If you have control over your schedule, traveling by plane in mid-pregnancy (14 to 28 weeks) is preferable because that's when the risks of miscarriage and premature labor are lowest, according to the Mayo Clinic.

The outlook is more restrictive for pregnant women with underlying medical issues such as heart disease or lung disease that could be exacerbated by air travel. They shouldn't fly at any point because of physiological changes -- an increased heart rate, higher blood pressure and less oxygen in the blood -- that take place at high altitude, the ACOG statement noted.

It updates a previous 2001 committee opinion with information from new studies that found air travel is generally safe for healthy pregnant women.

For pregnant women who travel constantly for work, flying can present a risk because of the exposure to cosmic radiation. This form of radiation comes from the sun and outer space and is more intense at higher altitudes. At one point it was thought the mother's body reduced a fetus's exposure to radiation; currently, this isn't believed to be the case, however.

Any passenger can calculate his or her exposure to cosmic radiation from a specific flight by visiting the Federal Aviation Administration's Web site tinyurl.com/cosmicrad.

Pregnant women who travel occasionally don't have to worry about radiation, even if they take long trips, the new ACOG statement said. Even the longest international flight will expose a passenger to no more than 15 percent of the recommended annual radiation limits.

jegraham@tribune.com