Dear Jennifer,
There are some relatively good studies done at The Pope Paul VI Institute looking at the risk of miscarriage with low progesterone levels. The researchers there, led by Thomas Hilgers, M.D., have also developed the protocol to which you refer. All the data is in the textbook: The Medical and Surgical Practice of NaProTechnology. You can also find some information on the Pope Paul VI Institute web site. The mainline obstetric literature also has an increasing number of articles regarding progestins and preterm labor prevention.
According to the Pope Paul VI Institute progesterone support protocol, at 17 weeks, a level of 64 is in zone 2 and the dose should be progesterone 100mg intramuscularly weekly for 2 levels then discontinue (assuming the levels remain in zone 3). It is important to note that the levels are “trough levels,” i.e., they are drawn right before the next shot is due.
The levels for the different zones rise as the pregnancy progresses, therefore we always consult the Pope Paul VI Institute graph to determine the zone at that time in the pregnancy and at that level.
At the Pregnancy and Family Care Centers of San Diego and Escondido we strongly recommend using progesterone supplementation according to the Pope Paul VI Institute protocol, i.e., for low levels, previous preterm labor or miscarriage, current preterm labor and other risk factors.
George Delgado, M.D., F.A.A.F.P.
Pregnancy and Family Care Centers of San Diego and Escondido
Voluntary Associate Clinical Professor,
Department of Family and Preventative Medicine,
School of Medicine,
University of California, San Diego