Shortly after conception, the human chorionic gonadotropin (hCG) glycoprotein hormone is secreted by the developing placenta. During early gestational growth, hCG rises in concentration. As a result, hCH is an excellent marker for the early detection of pregnancy. When the dielectrical properties of pregnant versus non-pregnant women are analyzed at microwave frequencies, the results indicate that the dielectric constant of the pregnant women's urine samples is smaller than the samples of non-pregnant women. In addition, the conductivity of the pregnant women's urine samples is higher than that of the non-pregnant women's samples. Microwaves thus offer an alternative in-vitro method of determining pregnancy. This finding came out of the Microwave Tomography and Materials Research Laboratory at Cochin University of Science and Technology (Kochi, India). The work was conducted by Anil Lonappan, Vinu Thomas, G. Bindu, and K.T. Mathew. C. Rajasekaran from the Medical College in Trivandrum also participated.
The researchers relied on in-vitro measurements using a cavity perturbation technique, which is employed in the frequency range from 2 to 3 GHz. The measurement setup comprised a transmission-type S-band rectangular cavity resonator and an HP 8714 ET network analyzer. The cavity resonator was made from a transmission line (waveguide or coaxial line) with one or both ends closed. It can be either transmission or reflection type. To test the results, the same samples were subjected to investigations in the clinical laboratory for quantitative analysis. Aside from being accurate, the cavity perturbation technique was found to be quick. It eliminated the reaction time found in test strips and midstream tests. See "Determination of Pregnancy Using Microwaves," Microwave and Optical Technology Letters, April 2007, p. 786.