Human Chorionic Gonadotropin (HCG) is produced by the placenta. It increases rapidly during the first trimester. Over the counter pregnancy tests identify pregnancy by detecting HCG. Some doctors think morning sickness is due to HCG.
There are limited studies on how HCG affects sleep in humans. In animal models, HCG was associated with decrease activity. This suggest HCG induces sleep. Some people taking HCG as part of a weight loss diet report improvement in sleep.