Serum free ß-human chorionic gonadotropin in the three trimesters of pregnancy: effects of maternal characteristics and medical history.

Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology

PubMedID: 25846870

Wright D, Papadopoulos S, Silva M, Wright A, Nicolaides KH. Serum free ß-human chorionic gonadotropin in the three trimesters of pregnancy: effects of maternal characteristics and medical history. Ultrasound Obstet Gynecol. 2015;.
OBJECTIVE
To define the contribution of maternal variables which influence the measured maternal serum free ß-human chorionic gonadotropin (ß-hCG) in screening for pregnancy complications.

METHODS
Maternal characteristics and medical history were recorded and serum free ß-hCG was measured in women with singleton pregnancies attending for three routine hospital visits at 11(+0) -13(+6) , 19(+0) -24(+6) and 30(+0) -34(+6) ?weeks' gestation. For pregnancies delivering phenotypically normal live births or stillbirths at =24?weeks' gestation, variables from maternal demographic characteristics and medical history important in the prediction of free ß-hCG were determined from a linear mixed effects multiple regression.

RESULTS
Serum free ß-hCG was measured in 94,985 cases in the first trimester 7,879 in the second trimester and 8,424 in the third trimester. Significant independent contributions to serum free ß-hCG were provided by gestational age, maternal weight, age, racial origin, cigarette smoking, method of conception, diabetes mellitus and family history of preeclampsia (PE) in the mother of the patient. The effects of some variables were similar and those for others differed in the three different trimesters. Random effects multiple regression analysis was used to define the contribution of maternal variables that influence the measured serum free ß-hCG and express the values as multiples of the median (MoMs). The model was shown to provide an adequate fit of MoM values for all covariates both in pregnancies that developed PE and in those without this pregnancy complication.

CONCLUSIONS
A model was fitted to express the measured serum free ß-hCG across the three trimesters of pregnancy into MoMs after adjustment for variables from maternal characteristics and medical history that affect this measurement.