P–373 Initial β-hcg levels and the increase rates after 2 days are effective in predicting pregnancy outcomes in single blastocyst transfer in frozen-thawed or fresh cycles
Authors: Özer G , Yuksel B , Duzguner I , Kahraman S 
Published: August 2021

Abstract

Study question
What is the role of the initial β-hCG value and the β-hCG rate of increase after 2 days in the predictability of the pregnancy outcomes?

Summary answer
The initial β-hCG values and β-hCG increase rates after 2 days are effective in predicting early pregnancy loss (EPL) and live birth rates (LBR).

What is known already
β-hCG is a glycoprotein-structured hormone secreted by the cyto syncytiotrophoblasts of the blastocyst and detected in the blood at the earliest 6–8 days after fertilization. The β-hCG level increases approximately by doubling in 48 hours in normal pregnancies. There are few studies conducted about the initial β-hCG values and the increase rates after 2 days on the pregnancy outcome of ART cycles and these studies indicated different threshold values and its level still remains unclear.

Study design, size, duration
This is a retrospective cohort study and was conducted at IVF and Reproductive Genetics Centre, Memorial Sisli Hospital, Istanbul, Turkey between January 2016 and December 2019. A total of 4605 including 3834 FET and 771 Fresh cycles resulted in a positive pregnancy test after a single blastocyst transfer was examined.

Participants/materials, setting, methods
The initial β-hCG test was applied 9 days after ET, when is the 14th day after ovulation. The latter β-hCG test was applied 2 days later. The cases with missing initial β-hCG tests or second β-hCG tests and missing follow-up during pregnancy were excluded. The mean β-hCG values and the increase rates after 2 days of the cases who had biochemical pregnancy loss (BPL), EPL and achieved live birth were reviewed.

Main results and the role of chance
The mean initial serum β-hCG level on 9 days after ET in the live birth group was 185.51 ±97.38 IU/L in FET cycles, which was significantly higher than the groups of BPL (62.75 ±50.70 IU/L) and EPL (133.93 ±95.10 IU/L). However, in fresh cycles, these levels in the live birth group was 167.70 ±114.05 IU/L which was significantly higher than the groups of BPL (50.13 ±27.49 IU/L) and EPL (106.55 ±71.80 IU/L).
The mean β-hCG levels in FET cycles were significantly found higher than in fresh cycles (P &lt; 0.005) regardless of pregnancy outcomes.
The β-hCG threshold value predicting live birth for fresh cycle was found 108 IU/L (sensitivity 71.5%, specificity 70.8%, PPV 87.% and NPV 46.3%), while this value was found 101 IU/L (sensitivity 81.4%, specificity 55%, PPV 81.6% and NPV 53.8 %) for FET cycles.
The β-hCG increase rate of threshold value predicting LBR for fresh cycle was 1.92 (sensitivity 90.6%, specificity 36.3%, PPV 80.1% and NPV 57%), while this rate was found 2.01 (sensitivity 90.1%, specificity 38%, PPV 78.4% and NPV 61.1%) for FET cycles.
The β-hCG increase rate was not different between fresh and FET cycles.

Limitations, reasons for caution
Retrospective study
Wider implications of the findings: The initial β-hCG values and the increases in β-hCG values after 2 days can be used as effective parameters in the diagnosis of pregnancy outcomes. Early prediction of pregnancy outcomes may help to the clinician to manage and follow-up high risk pregnancies.

Trial registration number
Not applicable