Dear Erica,
It certainly is possible that a low progesterone in the luteal phase (the part of your cycle after ovulation until the first day of the next menstrual bleed) and subsequently during the first trimester could be leading to your miscarriages. It would be important to know whether or not you have had any term pregnancies.
You should seek evaluation, preferably by a medical provider familiar with NaProTechnology. A NaProTechnology evaluation would start with a history and physical examination along with some blood tests. Then you would start charting your cycles with the Creighton Model Fertility Care System. This charting might demonstrate a short post-peak phase which would suggest a low progesterone level in the luteal phase of the cycle.
Based on the road map provided by the charting, a comprehensive hormone profile could be done from about five days prior to the peak day to eleven days after the peak day. Peak day refers to the last day, of peak-type or fertile-type mucus, (that mucus which is slippery, crystal-clear or stretchy), in a cycle.
Additionally, an ultrasound follicular series based on the road map could be used to confirm anatomically normal ovulation. Other considerations for testing include chromosomal analysis and tests of autoimmune disorders such as the anti-cardiolipin syndrome.
Since you are 42, you should get moving quickly as your natural fertility is waning.
George Delgado, M.D., F.A.A.F.P