Early detection of declining female fertility is important for effective pr
evention and treatment of infertility. Age, serum concentration of FSH in t
he early follicular phase (basal FSH), and the clomiphene citrate (CC) chal
lenge test correlate only with large declines in fertility. We serendipitou
sly discovered that by a novel mechanism bioelectric impedance (BEI) sensit
ively reflects early fertility decrements. BEI was measured between the rig
ht and left arms by the tetrapolar method before and during ovarian stimula
tion for in vitro fertilization (IVF). In a stepwise multiple logistic regr
ession analysis of five factors (BEI on luteal day 4 prior to the IVF cycle
[BEI-L4], age, basal FSH, body height, and body mass index), BEI-IA alone
was a significant predictor (P< 0.05) of achievement of pregnancy by IVF in
148 women (74 pregnant and 74 nonpregnant). BEI showed a nadir on the day
of administration of hCG in the pregnant but not the nonpregnant group. Ser
um concentrations of VEGF during ovarian stimulation were significantly hig
her in the pregnant group, but not those of 17 beta-estradiol and progester
one. The CC challenge test revealed no significant difference between 11 pr
egnant and 15 nonpregnant women. The clinical usefulness of BEI was evaluat
ed in 272 consecutive IVF cycles. Rate of pregnancy was significantly highe
r (P<0.01) in IVF cycles with BEI-L4 greater than or equal to 600 Omega tha
n <600 Omega (44% and 26% in 149 and 123 cycles, respectively). When BEI-IA
was greater than or equal to 600 Omega, pregnancy rates were constantly hi
gh irrespective of age and basal FSH. In prediction of nonpregnancy, sensit
ivity of BEI-IA (0.52) was significantly (P<0.05) higher than those of age
and basal FSH (0.39 and 0.046, respectively). BEI, which is easy, noninvasi
ve, and inexpensive, predicts female fertility more sensitively than age an
d basal FSH, probably reflecting angiogenic capacity of reproductive organs
.