Pregnancy Travel
The safest time for a woman to travel during pregnancy is in the second trimester, preferably month 4 through month 6; when there is the least risk of miscarriage (which would more likely happen prior to 12 weeks) and premature labor (which would be more likely after 28 weeks). Plus, during the second trimester, morning sickness has typically let up; allowing you to feel better and in addition, you are not big enough yet to feel too uncomfortable being out-and-about. Also, check with the airline as some have specific restrictions for pregnant women.
more on Travel in Pregnancy
International Travel When Pregnant