Serum progesterone and estradiol-17beta levels in premature and term labor.

A total of 30 to 50 per cent of premature labors occur without identifiable predisposing conditions. To evaluate the hormonal status of these pregnancies, serum progesterone (P) and estradiol (E2) were measured by radioimmunoassay singly in 60 premature labor patients and serially in 19 normal pregnancies. Premature labor patients as a group have significantly lower P and E2 levels than controls. Pregnancies complcated by idiopathic premature labor (IPL) (p less than 0.01), premature labor secondary to abruptio-marginal separation (A-MS) (p less than 0.05), and premature rupture of membranes (PROM) (p less than 0.05) have significantly lower P levels than controls. Patients with IPL and A-MS have significantly lower P levels (p less than 0.01) than PROM patients. No significant change in P or E2 occurs immediately prior to normal term labor. Conclusions are that (1) premature labor patients have significantly lower Pand E2 levels than controls, (2) the degree of P depression varies according to the type of premature labor and (3) IPL is characterized by premature labor with no identifiable predisposing factors.