Materials and Methods

Patients

In this retrospective study, participants were early pregnancy women who visited the clinic between July 2017 and December 2018 in Ningbo First Hospital, China. We estimated the gestational age according to the date of last menstrual period of women with regular menstrual cycle and ovulation date of women with irregular menstrual cycle. The inclusion criteria were intrauterine singleton pregnancy, gestational age between 4 weeks to 10 weeks. The exclusion criteria were chemical pregnancy, ectopic pregnancy, multiple pregnancy, pregnancy through in vitro fertilization, chromosome abnormity in either of the couple. Clinical information of the patients was recorded at their first visit. The study was approved by the ethics committee of Ningbo First Hospital.

Study Design

Patients were divided into the ongoing pregnancy group and the inevitable abortion group according to their early pregnancy outcomes. Criteria of the ongoing pregnancy group included intrauterine pregnancy with primitive cardiac beat, embryo size on ultrasonography corresponded to the calculated gestational age, without or just a little vaginal bleeding. Participants were classified to the inevitable abortion group when meeting any of the following conditions: persistent vaginal bleeding or abdominal pain, followed by expulsion of the embryo; failed to detect embryo’s cardiac beat for two or more ultrasonic tests after 7 weeks of gestational age; normal cardiac beat disappeared. The end of follow-up time of this study was 12th week of gestational age.
Patients took venous blood test detecting serum reproductive hormones every one or two weeks until the 10th week of pregnancy. The E2 and β-HCG levels were recorded and compared at 4 weeks ±2 days, 5 weeks ±2 days, 6 weeks ±2 days, 7 weeks ±2 days, 8 weeks ±2 days and 10 weeks ±2 days of gestational age. Growth rates of the two hormones were analyzed and compared. Receiver-operating characteristic (ROC) curves analysis of E2 from the 5th to 8th week of gestational age were generated..
We classified the variation of E2 into four types: a: persistent increase; b: slow increase or fluctuation; c: continuous decrease; d: sudden drop. The four types of variation were compared between the two groups.

Statistical Analysis

Statistical analysis of the clinical data was performed by SPSS Statistics version 19.0(SPSS Inc., Chicago, IL, USA). Continuous data were compared with Student’s t-test or Mann-Whitney U test for non-parametric variables. Categorical data were compared with Chi-square test or Fisher’s exact test where appropriate. ROC curves depicting predicted probabilities were generated from logistic regression models of pregnant outcomes. P -values that are smaller than 0.05 were considered statistically significant.