High progesterone levels are not an accepted indication of being pregnant with twins; rather, high levels can indicate pregnancy, cancer or overproduction of hormones, notes Everyday Health. The most accurate way to learn if the pregnancy is one fetus or multiple fetuses is to have an early ultrasound, notes BabyCenter.
The experts at BabyCenter state that an ultrasound is the best method for revealing multiple pregnancies, particularly for women who are more than six to eight weeks pregnant. An early ultrasound can also be ordered if the doctor or nurse hears more than one heartbeat with the Doppler.
According to Everyday Health, high progesterone levels could also indicate a molar pregnancy or an adrenal gland issue. It lists the typical progesterone range for the first trimester of pregnancy as 10 to 44 nanograms per milliliter or 32.6 to 140 nanomoles per liter.