Maternal physiological changes in pregnancy range of effects during the pregnancy. Pregnant women experience numerous adjustments in their endocrine system that help support the developing fetus. The fetal-placental unit secretes steroid hormones and proteins that alter the function of various maternal endocrine glands. Sometimes, the changes in certain hormone levels and their effects on their target organs can lead to gestational diabetes and gestational hypertension. Levels of progesterone and estrogen rise continually throughout pregnancy, suppressing the hypothalamic axis and subsequently the menstrual cycle. The progesterone is first produced by the corpus luteum and then by the placenta in the second trimester. Women also experience increased
Menstrual synchrony of the thawed axillary pad under their noses daily. The researchers concluded that odorless compounds collected from women during the late follicular phase of their menstrual cycles triggered hormonal events that shortened the menstrual cycles of the recipient women, and that odorless compounds collected from women during the time of ovulation triggered a hormonal event in the recipient women that lengthened their menstrual cycles. Stern and McClintock concluded that these findings "proved the existence of human pheromones" as well as illustrated manipulation of the human menstrual cycle. Researchers pointed out several flaws in their study. Whitten's main critiques was with