Study design
This is a unblinded randomized study conducted at the Center for Reproduction and Genetics of the Affiliated Hospital of Shandong University of Traditional Chinese Medicine (TCM). This study was approved by the University Research Ethics Committee and registered at the China Clinical Trial Registration Center (ChiCTR1800017209). All participants signed an informed consent form prior to the study enrollment.
Study participants
A total of 300 infertile patients undergoing FET were recruited from the Center for Reproduction and Genetics of the Affiliated Hospital of Shandong University of TCM, from 19 July 2018 to 24 February 2019, during this period, patients undergoing embryo transfer will be included after signing informed consent.
Inclusion criteria were as follows: 1) at least one cycle of IVF/intracytoplasmic sperm injection (ICSI) performed in our reproductive center; 2) female age ≤ 35 years; 3) a body mass index (BMI) between 18.5 kg/m2 and 25 kg/m2; 4) regular menstrual cyclicity (24-35 days); 5) the attending physician for embryo transfer being the same person for all patients; 6) the tubal factor is the cause of female infertility( bilateral tubal obstruction, or hydrosalpinx treated using laparoscopic surgery); 7) Four or more embryos available for transfer with at least one viable day 3 embryo with a score of 6 or above according to the Istanbul Consensus [20] and without receiving preimplantation genetic screening (PGS) or preimplantation genetic diagnosis (PGD).
Exclusion criteria were as follows:1) patients with known congenital uterine malformation, uterine fibroids, or endometriosis; 2) chromosomal abnormalities in any of infertile couples; 3) female with immune diseases.
Randomization
Patients are randomly grouped according to the random list generated by the computer. The exact time of randomization was on the day of endometrial transformation. Randomization via website (www.randomization.com). The online randomization program was operated by a special data expert, who did not participate in patient recruitment and clinical management. The person then prepares the randomly grouped cards and puts them in an opaque envelope. On the day of randomization, the subjects were randomly divided into two groups according to the opaque envelope. Group A was subjected to have intercourse using a condom at the night before embryo transfer, while group B was subjected to abstain for the entire IVF cycle. Signed written informed consents were obtained from all participants before the study. Information about whether patients engage sexual intercourse using the barrier contraception or to abstain one night before FET is sealed in an opaque envelope with only one number on it. In order to prevent patients from not following the doctor's orders, we will contact the patients and their spouses again according to the results after unblinding to confirm that the content provided is true.
Interventions
In the present study, artificial endometrium preparation by the exogenous administration of estrogen and progesterone was used for the FET cycle. To prepare the endometrium, all patients self-administered oral estradiol valerate (France; DELPHARM Lille S.A.S.) 8 mg per day started at the third to fourth day of the menstrual period for 5 days, and then 12 mg per day for the remaining days of the cycle, which was adjusted according to the clinical situation during this period. Estrogen administration was continued until the endometrium reaches a thickness of 8 mm (determined by an ultrasonographic examination). And then progesterone was combined to initiate the secretory phase in preparation for FET. Two vitrified-warming embryos were selected for transfer on the fourth day of progesterone administration based on morphological grading according to the Gardner and Schoolcraft scale. Luteal support was routinely provided after FET for 14 days irrespective of pregnancy. For patients confirmed with a clinical pregnancy, estradiol valerate and progesterone were continued until 10 weeks of gestation, which was gradually reduced until detecting the fetal heart beats.
Participant follow-up and data collection
The primary outcome was clinical pregnancy rate, which was defined as the detection of fetal heart beats using ultrasonographic examinations 35 days after FET. Serum beta subunit of human chorionic gonadotropin (β-hCG) levels were examined using electrochemiluminescence analysis (Cobas e411 System Product, Germany) on day 14 following embryo transfer in all patients. Implantation was defined as a serum quantitative β-hCG ≥10 U/L. All pregnancies were followed until 7 weeks after FET. A biochemical loss is defined as a transient but significant increase in serum β-hCG ≥10 U/L between days 12 and 20 after embryo transfer without detecting a gestational sac by an ultrasonography. An early abortion is defined as the detection of an empty gestational sac using ultrasonographic examinations before 12 weeks of gestation. Implantation rate is defined as the ration of the number of embryos implanted and the number of transferred embryos.
Sample size calculation
The sample size calculation was done based on previous studies, in which the efficacy of sexual intercourse during the peri-transfer period was 24% [10], α = 0.05 and β= 0.2. According to the ratio of 1:1, 10% of the lost visit rate, there were expected to be 104 patients in the barrier contraception group and 104 patients in the abstain group.
Statistical analysis
The statistical software package, IBM SPSS Statistics for Windows, version 22.0 (IBM Corporation, Armonk, NY, USA), was used for all data analyses. The data are expressed as mean ± standard deviation (x ± s). Among those were normally distributed and homogeneity of variance (homoscedasticity) was satisfied, a t test was performed; otherwise, Mann-Whitney U test was performed. The treatment outcomes for each group were counted and expressed as a frequency. When the total sample size was greater than 40 and the minimal theoretical frequency was greater than 5, we applied the Chi-square test. When the total sample size was less than 40 or the minimal theoretical frequency was less than 5, we applied the Fisher exact-probability method. P<0.05 was considered statistically significant. The intention to treat analysis will not be performed because we had only one intervention after randomization and did not use any experimental drugs.