DOI: 10.5061/dryad.8931zcrnj
title: Association between seven-day serum β-hCG levels after frozen–thawed embryo transfer and pregnancy outcomes: a single-centre retrospective study from China

description: Objective: Early monitoring of plasma human chorionic
 gonadotropin (β-hCG) level is vital in predicting pregnancy outcome. This
 study investigated the predictive value of serum β-hCG level on the 7th
 day after frozen-thawed embryo transfer (FET) for ongoing pregnancy (OP)
 and adverse pregnancy (AP). Design: Retrospective study
 Setting: The Reproductive and Genetic Center of the Affiliated
 Hospital of Shandong University of Traditional Chinese Medicine, China.
 Participants: 1,061 pregnant women who underwent FET between January 2014
 and January 2017.   Primary and secondary outcome measures:
 Pregnancy outcome. Results: Serum β-hCG levels on the 7th day after FET
 were higher in the single OP group compared to the biochemical pregnancy
 (BP) group (p ＜0.001). Besides, the serum β-hCG cutoff level at 4.34
 mIU/mL on the 7th day showed high predictive value (area under the curve
 [AUC] = 0.852). Serum β-hCG levels on the 7th day after FET were higher in
 the twin OP group compared to the single OP group (p＜0.001). Also, the
 serum β-hCG cutoff level at 17.95 mIU/mL on the 7th day showed high
 predictive value (AUC = 0.903). Serum β-hCG levels on the 7th day after
 FET were lower in the ectopic pregnancy (EP) group compared to the single
 OP group (p ＜0.001) whereas, serum β-hCG cutoff level at 4.53 mIU/mL on
 the 7th day exhibited a high predictive value (AUC = 0.860). Further, the
 serum β-hCG levels on the 7th day after FET were lower in the single early
 spontaneous abortion (SA) group compared to the single OP group (p＜0.001)
 while the serum β-hCG cutoff level at 5.34 mIU/mL on the 7th day exhibited
 high predictive value (AUC = 0.738). Conclusion: Serum β-hCG on
 the 7th day after FET has good clinical significance for the prediction of
 OP and AP.
description: <b>Patient and public
 involvement</b><br> This study was designed
 without patient participation, they were not invited to contribute to the
 study design and to develop patient-relevant outcomes or interpret the
 results. Also, patients did not contribute to the writing or editing of
 this document for readability or accuracy. <b>Assisted pregnancy
 method</b><br> The replacement cycle was adopted
 to prepare the endometrium at our center. The study participants were
 administered with Progynova (four tablets per day) for 5 days, starting
 2-4 days after the first day of the last menstrual cycle. Progesterone was
 administered when the endometrial thickness was 8 mm to induce the
 transformation of the endometrium to the secretory phase. Thereafter, the
 patient was prepared for FET. We routinely provided 14 days of luteal
 support after FET irrespective of pregnancy. For patients with ongoing
 pregnancy, progynova and progesterone were continued for 10 weeks of
 gestation, and after confirming the presence of the fetal heart, the
 dosage was gradually reduced. <b>Measurement of serum
 β-hCG</b><br> At 7 and 14 dpt, venous blood was
 collected at 8:00–9:00 AM and centrifuged. β-hCG was measured from the
 collected serum via chemiluminescence.  <b>Grouping criteria for pregnancy
 outcomes</b><br> BP refers to serum β-hCG
 &gt; 5 mIU/mL after FET but with no gestational sac. Ultrasound
 examinations were performed on the 35<sup>th</sup> day
 after FET to detect the fetal heartbeat, which was defined as a clinical
 pregnancy. The pregnancy outcome was classified as a normal pregnancy or
 adverse pregnancy (AP). Further, normal pregnancy was classified as either
 single or twin OP. The single OP refers to a single
 pregnancy with normal fetal development verified through obstetrical and
 ultrasound examination on or after the 12<sup>th</sup> gestational week. Twin OP refers to twin pregnancy exhibiting normal fetal development, which was verified through obstetrical and ultrasound examination on or after the 12<sup>th</sup> gestational week. AP included EP, BP, and single SA. EP refers to the presence of an extrauterine mass but without a gestational sac in the uterus. Early SA refers to natural spontaneous abortion before the 12<sup>th</sup> gestational week.