Most moms carrying twins go into labor at 36 to 37 weeks, as opposed to 40 in a single pregnancy, Al-Khan says, and some may go even earlier. Generally, if the twins are born after 34 weeks, there should not be a major concern, but a premature baby is still a premature baby, he says.
False pregnancy in humans is less common, and may sometimes be purely psychological. It is generally believed that false pregnancy is caused by changes in the endocrine system of the body, leading to the secretion of hormones that cause physical changes similar to those during pregnancy.
In rare cases, even men can have a false pregnancy. Some men experience a related phenomenon known as couvade, or sympathetic pregnancy. They will develop many of the same symptoms as their pregnant partners, including weight gain, nausea, and backache.