Not necessarily. So don't invest in blue baby clothes just because you're lucky enough not to have morning sickness.
There is some evidence, however, that hormones produced by girl babies can make moms more nauseated early in pregnancy than they would be if they were carrying a boy.
And research suggests that moms who have severe nausea (hyperemesis gravidarum) during pregnancy in the first trimester may be a bit more likely to have girls: A Swedish study of over 1 million women who had hyperemesis gravidarum found that 55 percent delivered girls. But this study was done with moms-to-be who were hospitalized because of the nausea, and experts aren't sure how their findings apply to women who suffer from more typical morning sickness.
The midpregnancy ultrasound that many moms have when they're 18 to 22 weeks along is a much more reliable — although not foolproof — way of determining the sex of your baby. And of course if you have an amniocentesis for some reason, you'll be able to find out whether you're having a boy or a girl with 100 percent certainty.
Some testing centers and doctor's offices are also now offering a new blood test that uses a baby's DNA to detect chromosomal conditions at 9 weeks of pregnancy or later. This test is noninvasive and reveals the baby's sex, too.