Maternal estradiol and progesterone concentrations among singleton spontaneous pregnancies during the first trimester

Pregnancy hormonal milieu represents a crucial determinant of fetal outcome. We aim to determine 17β-estradiol (E₂) and progesterone (PGT) concentrations in spontaneous pregnancies during the first trimester. In addition, we aim to determine E₂ concentrations as a function of gestational age (GA) and PGT.

Between November 2015 and March 2017, 104 healthy women of at least 18 years undergoing medical consultation for voluntary interruption of pregnancy were enrolled in an observational study at University Hospital ASST Fatebenefratelli Sacco, Milan, Italy. Only singleton pregnancies between 5⁺⁰ and 13⁺⁶ weeks of gestation were eligible. First trimester ultrasound scans were performed for dating and one fasting venous blood sample was collected for E₂ and PGT determinations.

E₂ and PGT concentrations steadily increased according to GA. The correlation between E₂ on a logarithmic scale and PGT concentrations was expressed by the following equation, explaining 12.6% of E₂ variance: logE₂ = 2.57 + 0.1 × PGT, (r = 0.34, p < 0.001). By performing a multivariable linear regression analysis adjusted for variables significantly correlated with E₂ concentrations, we obtained a model explaining the 53.5% of E₂ variance. The final equation to determine E₂ concentrations among Caucasian women was: logE₂ = 1.96 + 0.01 × GA + 0.004 × PGT.

Gestational week-specific reference intervals are reported for maternal E₂ and PGT concentrations during early pregnancy, further providing a model for E₂ assessment in this period. This will represent a starting point for further evaluations between twin and ART pregnancies, as well as to potentially improve pregnancy outcome and future health of the offspring.