Pregnancy rate in intrauterine insemination, is uterine biophysical profile of predictive value? A prospective study

Abstract

Purpose

This study aimed at evaluating the value of uterine biophysical profile (UBP) scoring to predict the pregnancy rate after IUI.

Methods

This prospective study was carried out on 85 women who were referred to our tertiary teaching center with infertility of male factor or unknown etiology infertility in 2018. To measure the uterine biophysical criteria, transvaginal ultrasonography (TVS) was performed on the day of beta-human chorionic gonadotropin (B-hCG) injection, and the results were evaluated based on positive B-hCG.

Results

85 patients were included with a mean age of 30 years; of those 12 (14.1%) were able to conceive. UBP (p = 0.151) and it’s parameters (including endometrial thickness, number of endometrial layers, myometrial echogenicity, uterine artery pulsatility index, myometrial blood flow internal to arcuate vessels, endometrial blood flow in the third zone of endometrium, myometrial contraction frequency, and ovarian follicle (OF) size [p = 0.05, 0.89, 0.59, 0.79, 1, 1, 0.59, and 0.77, respectively]) were not significantly associated with pregnancy rate. 91.7% of the cases with positive pregnancy test results, had a UBP score of > 13; however, UBP score was not meaningfully associated with IUI treatment success rate (p = 0.15).

Conclusions

UBP scoring system seems to need more data for external validation, or it might require modifications before implementation, as it may cause false reassurance.

Background

Infertility is defined as the inability to become pregnant after a year of regular unprotected coitus [1–3]. The fertility rate of normal couples is postulated to range between 20 and 25%; hence 90% of these couples will have a living child after one year [4]. Almost a quarter of Iranian couples experience primary infertility during their connubial life; of those, 3.4% are struggling with infertility at any particular time [5]. About 10–15% of couples may take advantage of specialized methods of assisted reproductive technology (ART) [6]. Given that infertility may lead to psychological issues, marital life instabilities, increased remarriage rate, and considering societal repercussion and personal suffering that infertility brings about, it attracts a lot of attention in the press [7]. In recent years, diagnostic and therapeutic modalities and strategies for infertility have gone through tremendous changes; nevertheless, the success rate of these techniques has been reported to be around 30–40% [8]. The main impediment in treating infertility is the low rate of embryo implantation during infertility treatment cycles, such that embryo implantation has been calculated to be only 15% [9]. Nevertheless, despite extraordinary efforts in applying ART, it seems that a high percentage of infertile couples fail to give a live birth due to unknown causes of infertility and fetus rejection. Reportedly, the prevalence of infertility has remained the same over time, and even slightly increased prevalence has been proposed in some areas [10]. One of the inveterate methods of ART is intrauterine insemination (IUI), which includes strategies directing sperm to different parts of a woman’s uterus [11]. IUI is a simple and inexpensive therapeutic method of ART, offering hope to certain infertility cases, including male-factor-related infertility, unexplained infertility, and factors associated with the cervix.

Because of the low success rate of this method, reported by some studies as < 1% of live baby delivery in each cycle [12] and since performing and repeating the cycles can impose extravagant expenses on the patients, developing a way to predict the success rate of IUI and pregnancy initiation anticipatedly is of pivotal importance and can be a solution for mitigating the psychological and financial burden imposed on infertile couples and health care systems. Nowadays, gynecological ultrasonography is considered an efficient way of evaluating the uterus in ART, and recently testing the value of ultrasound indices in predicting the success rate of assisted reproductive programs has drawn a lot of attention [13, 14]. Besides, an appropriate endometrial condition has been indicated to be one of the main factors of successful implantation, while poor blood flow in the uterus is one of the failure-predicting factors in ultrasound reportedly [15].

Considering the impact of infertility on our society, the increasing rate of employing ARTs (especially IUI), and the lack of similar studies in Iran on this area of research, we designed and conducted the current study to assess the value of ultrasound-derived uterine biophysical profile (UBP) in the prediction of the IUI success rate.

Methods

Study design and population

This prospective study was conducted on 85 infertile female patients who were referred to our tertiary teaching health care center in 2018. All patients included were infertile because of male factor (no identifiable reproductive impairment found in female partner) or unknown etiology, aging from 20 to 38 years. Patients with FSH < 12 mIu/ml on the third day of conception and no history of uterine surgery, genital injuries, or failed IUI, were considered eligible and entered our study. Female patients with or suspicious of female factors of infertility, including cervical problems, thick mucus, uterine abnormalities, and endometriosis, were excluded.

Ethical considerations

This study was approved by the institutional Ethics Committee. Informed consent, as per the WHO guidelines, was acquired from all participants. Any additional charges were paid by researchers, and the patient’s information was kept confidential.

Uterine biophysical profile (UBP)

A skilled radiologist (with 23 years of experience in gynecological imaging) performed vaginal probing (7–9 MHz) and TVS exam (Siemens, G40, Siemens, Germany) and undertook cycle monitoring as following follicular size and number, and endometrial thickness and pattern at second and fourth day of menstrual cycle and then every day until ovulation trigger day (Fig. 1). On the day of the ovulation trigger, patient underwent TVS exam just before B-hCG injection, determining (a) endometrial thickness and pattern, and (b) number of OFs measuring 18–24 mm (by averaging maximum three orthogonal diameters). On the day of insemination, patient underwent TVS exam to (a) identify the uterus positioning (facilitating endometrial cavity access during IUI), and (b) assigning UBP score to any patients as per previous studies and following UBP scoring system (a modified version of Applebaum scoring system) presented in Table 1 [16, 17].

Fig. 1.

Grayscale and Doppler transvaginal ultrasound examination for UBP scoring. a Unilayer thickened echogenic endometrium (thickness: 16 mm) is noted between arrows. b Thickened endometrial line with a distinct trilaminar pattern (between arrows). c Three folicles are indicated with arrows, which are bounded by thin and smooth borders. The size of largest antral follicule (thick arrow) was recorded for any case. Arrowhead demarcates a corpus luteum. d Heterogenuous myometrium, and thin endometrium (thickness: 6 mm) with a hazy trilaminr appearance. e Notice the blood flow detected in Zone A

Table 1.

The uterine biophysical profile scoring system

Variables	Score	Variables					Score
EMT		Myometrial echogenicity
< 7 mm	0	Coarse/heterogeneous					1
7–9 mm	2	Homogenous					2
10–14 mm	3	UA-PI
> 14 mm	1	> 3					0
EMP		2.5–2.99					1
No layering	0	2.2–2.49					2
Hazy trilaminar	1	< 2.19					3
Distinct trilaminar	2	EBF
MCF		Absent					0
< 3 contractures in 2 min	0	Sparse					2
> 3 contractures in 2 min	1	Abundant and multifocal					5
MBF on gray scale
Absent	0
Present	2

EBF endometrial blood flow in 3rd zone of the endometrium, EMP endometrial pattern, EMT endometrial thickness, MBF myometrial blood flow internal to arcuate arteries, MCF myometrial contraction frequency, UA-PI uterine artery pulsatility index.

Endometrial thickness (EMT)

EMT was measured in a med-sagittal plane as the maximum distance between the anterior and posterior endometrial-myometrial junctions.

Endometrial pattern (EMP)

EMP was reported as the number of alternating echogenic/hypoechoic endometrial layers discernible between anterior and posterior endometrial-myometrial junctions (e.g., 5-line or ‘trilaminar appearance’ which is consisted of hypoechoic internal endometrium, sandwiched between outer well-defined hyperechoic layer and a central echogenic line made at mucosal apposition).

Sharpness (hazy versus distinct) of transitioning between inner hypoechoic and outer hyperechoic layers of endometrium was also recorded.

Myometrial contraction frequency (MCF)

Myometrial contractions are visualized in TVS as wave-like endometrial movements. Contraction frequency was recorded as the number of moves during 2 min.

Endometrial blood flow (EBF)

To evaluate endometrial vascularity, the endometrium is divided into the following four zones [16, 17]:

1. Zone 1 A 2 mm thick area surrounding the hyperechoic outer layer of the endometrium

2. Zone 2 The hyperechoic outer layer of the endometrium

3. Zone 3 The hypoechoic inner layer of the endometrium

4. Zone 4 The Endometrial cavity

EBF was assessed on sagittal color and power Doppler scan of the uterus, placing the color box over the thickest part of the endometrium. Pulse Repetition Frequency was set at 0.3, and the lowest wall filter was chosen. The presence or absence of color within the third zone of the endometrium (when blood vessels reached out intervening hypoechoic layer) was reported.

Pulsatility Index of Uterine Artery (UA-PI)

The Doppler gate was placed over uterine arteries lateral to the cervix before they enter the cervix, and spectral waveform of the arteries were observed and analyzed. Pulse Repetition Frequency was set at 0.3, and the lowest wall filter was chosen not to miss out slow end diastolic flows. Pulsatility index (PI) was measured as peak systolic velocity minus end diastolic velocity divided by mean velocity. The average of left and right UA-PIs was recorded as the final value.

Myometrial echogenicity

Myometrium was assessed while scanning the uterus in the longitudinal plane. It was reported as uniform (homogeneous) or non-uniform (coarse inhomogeneous or heterogeneous) echogenicity when assessed for on grayscale B-mode ultrasound exam.

Myometrial blood flow (MBF)

Myometrial blood flow internal to the arcuate arteries was looked for on grayscale B-mode ultrasound exam.

Intrauterine insemination (IUI)

Patients were approached as per national IUI protocol. Two letrozole pills (Iran Hormone, Iran) were given to all patients on fifth through ninth day of their menstruation cycle. The IUI was undertaken not earlier than (a) finding an OF measuring 14 mm or larger in TVS between 12 and 14th days of menstruation, and (b) when serum estradiol level of 200 pq/ml or more.

Insemination was performed using a Wallace catheter (Wallace, Wallace, USA), inserting 0.3–0.4 mL ready and concentrated sperm. Sperm was prepared through sperm washing, diluting the sample in the butter solution, centrifuging it at a low speed, and then harvesting the supernatant. After two or three rounds of centrifugation, the deposited solution was suspended and inoculated. Then, 16 days after the inoculation, serum B-hCG was measured via radioimmunoassay.

Finally, 16 days after the insemination, the pregnancy outcome for any patient was assessed using B-hCG, and B-hCG > 10 was considered as desired positive pregnancy outcome.

Statistical analysis

Raw data were analyzed by SPSS v. 22.0 (IBM Inc., Chicago, Ill., USA). Firstly, the normality of quantitative variables was assessed using the Kolmogorov–Smirnov test, which confirmed a non-normal distribution to our data. Therefore, to compare the mean value of the quantitative variables, t-independent or Mann–Whitney U-test were implemented; and to compare categorial variables, the Chi-square or Fisher's exact test was used. The level of significance was set at P ≤ 0.05.

Results

The present study included 85 infertile women undergoing ART, with a mean age of 29.41 ± 6.1 years. Generally, 53 (62.3%) patients had primary infertility, and 32 (37.7%) had secondary infertility. The mean endometrial thickness (EMT) of the participants was 8.06 ± 1.61 mm. one of the patients (1.2%) had no perceptible endometrial layer in TVS, 6 (7.1%) patients had only a single-layered endometrium, 7(8.3%) patients showed no endometrial layering, one (2.1%) patient had a three-layered, and 77 (90.6%) patients had a 5-layered (distinct trilaminar) endometrium. Additionally, the echogenicity of the uterus in 77 (90.6%) patients was homogeneous, while it was heterogenous in the remaining 8 (9.4%) patients. The mean uterine artery pulsatility index (UA-PI) was 1.16 ± 0.87. Endometrial blood flow (EBF) was present in 15 (17.6%) patients in Zone 3. Uterine contractions were found in 77 (90.6%) cases, more than three contractions in 2 min. The mean size of the largest OFs found was 20.05 ± 4.07 mm, and the mean UBP score was measured to be14.89 ± 2.88. The B-hCG on the 16th day after inoculation (pregnancy) was negative in 73 (85.9%) patients and positive in 12 (14.1%). Table 2 demonstrates the UBP score ranges in participants, cross-tabulated with pregnancy test results.

Table 2.

Uterine biophysical profile according to final pregnancy outcome

Pregnancy test	Uterine biophysical profile
	< 13	13–15	16–18	18
Positive	1 (8.3%)	2 (16.7%)	8 (66.7%)	1 (8.3%)
Negative	12 (16.4%)	24 (32.9%)	34 (46.6%)	3 (4.1%)

Frequencies presented as number (percentage)

With increasing age, no significant shift in pregnancy test results was noticed (p = 0.16). The primary or secondary nature of infertility was not significantly predictive of following pregnancy test result as well (p = 0.738) (Table 3).

Table 3.

Impact of age and infertility type on pregnancy rate

Variable	Pregnancy		p-value
	Positive	Negative
Age (year) †	27 ± 6.32	29.78 ± 6.02	0.16
Type of infertility‡
Primary	7 (12.3%)	46 (87.7%)	0.738
Secondary	5 (15.7%)	27 (84.3%)

^†Data presented as mean ± SD

^‡Data presented as number (percentage)

Moreover, EMT (p = 0.05), EMP (p = 0.89), myometrial echogenicity (p = 0.59), UA-PI (p = 0.79), EBF (p = 1), MBF (p = 1), MCF (p = 0.59), OF size (p = 0.77), and UBP (p = 0.15), all were not significantly predictive of pregnancy result test (see Table 4).

Table 4.

Impact of UBP score and UBP parameters on pregnancy rate

Variable	Pregnancy		P-value
	Positive	Negative
EMT (mm) †	7.93 ± 1.63	8.88 ± 1.32	0.059*
EMP‡			0.891**
No layering	0 (0%)	1 (100%)
Hazy trilaminar	2(28.6%)	5 (71.4%)
Distinct trilaminar	10 (13%	67 (87%)
Myometrium echogenicity**			0.594***
Homogeneous	12 (15.6%)	65 (84.4%)
Heterogeneous	0 (0%)	8 (100%)
UA-PI†	1.1 ± 0.51	1.17 ± 0.92	0.796**
MBF‡			1***
Yes	2 (13.3%)	13 (86.7%)
No	10 (14.3%)	60 (85.7%)
MCF‡			0.594***
< 3 contractions in 2 min	12 (15.6%)	65 (84.4%)
> 3 contractions in 2 min	1 (12.5%)	7 (87.5%)
OF size (mm)†	20.27 ± 2.37	20.01 ± 4.4	0.775*
EBF‡			1
Absent	10 (14.3%)	60 (85.7%)
Sparse	2 (14.3%)	12 (85.7%)
Abundant	1 (100%)	0 (0%)
UBP score†	16.08 ± 1.67	14.69 ± 3	0.151****

EBF endometrial blood flow in 3rd zone of endometrium, EMT endometrial thickness, MBF myometrial blood flow internal to arcuate arteries, MCF myometrial contraction frequency, OF ovarian follicle, UBP uterine biophysical profile

^†Data presented as mean ± SD. ^‡Data presented as number (percentage).

*t-test; **Mann–Whitney U-test; ***Chi-square test. ****Independent t-test

Discussion

Eighty-five infertile women were studied in our investigation with a mean age of roughly 30 years; of those12 (14.1%) conceived successfully. Various studies suggest that the IUI success rate is somewhere between 6 and 26% [18, 19]. We found no significant association between patient’s age and pregnancy outcome, as opposed to some other studies [20].

There is much controversy on the predictability of the UBP score and its parameters to anticipate fertility rate in patients undergoing ARTs (particularly IUI). Some studies have claimed that EBF is a stronger predictor of pregnancy rate comparing to other UBP parameters, such as EMT and EMP [21]. Our study did not show a meaningful association between pregnancy rate and UBP score or any single one of its parameters individually (neither EBF nor EMT / EMP). Although the average UBP score in patients with positive pregnancy test was generally higher than that of the patients with negative pregnancy test (UBP score was greater than 13 in 91.7% of patients who finally conceived), there was no significant association between UBP score and subsequent fertility rate (p = 0.151). The aforementioned inference is in accord with a study by Gupta et al. that scored UBP of 55 infertile Indian women and proposed that there is no statistically convincing association between the parameters of UBP and later pregnancy outcome [22] (20). Contrariwise, Thahkur et al. investigated 30 infertile women with unknown factor of infertility to test the predictability of UBP for subsequent fertility rate and suggested that UBP is an expeditious prognosticator capable of anticipating pregnancy rate post-IUI [23]. Khan et al. concluded in like manner, claiming that UBP score can effectively predict pregnancy outcome after embryo transfer in IVF cycles [24].

In keeping with our results, Masrour et al. found that EMT and EMP are uncorrelated with pregnancy rate, although the EBF on the day of IUI was greater in patients with successful final pregnancy outcome [25]. Tsai and colleagues analyzed 110 women undergoing IUI treatment cycles and reported 16 successful conceptions (14.5%) with no significant relation between endometrium thickness and pregnancy rate following IUI [26]. Weiss et al. came to the same conclusion and found that EMT is not predictive of subsequent fertility rate in IUI [27]. In contrast, some studies reported that EMP is a reliable indicator of IUI outcomes [25, 28]. Liu et al. showed that the pregnancy rate in patients with EMT of 10.5–13.9 mm is higher than that of patients with thinner endometrium [29]. As per our conclusions, Weiss et al. reported no meaningful correlation between EBF and fertility rate after IUI [27], although the opposite statement has been made in other works [30].

UA-PI or Resistive Index (RI), as readily taken doppler measurements, have been reported to be predictive of fertility rate post ARTs [28, 30]. Other reports, in line with our findings, suggested no significant relationship between UA Doppler indices and pregnancy rate after ARTs [26, 31]. By way of illustration, Kim et al. conducted a study on 106 infertile women in South Korea undergoing IUI treatment and found no significant difference between UA-RI of patients who subsequently became pregnant and those who did not [30]. Moreover, Prasad et al. reported that the UA-RI is not a significant predictor of IVF outcome and suggested that the doppler indices of UA may vary in patients with different etiologies of infertility [31].

MCF, reported as the number of wave-like movements in endometrium within 2 min continuous, has been proposed as a UBP parameter that can predict post-IUI pregnancy rate independently [30]. Furthermore, Swierkowski et al. demonstrated that a low frequency and high intensity of uterine contractility at the day of IUI is associated with a higher pregnancy rate [32]. Contrarily, our study did not find MCF predictive of fertility rate.

The largest OF size in ultrasound has been proposed as a prognosticator of post ART fertility [17]. Tsai et al. showed no meaningful association between OF size on the day of IUI treatment and following pregnancy outcome [26], which is in keeping with our results.

This study is subjected to some limitations. Firstly, small sample volume in the subgroup with positive pregnancy test, can surely affect the predictability of the UBP score and its subsetting parameters. Further studies on larger scale populations can overcome ensuing biases. Secondly, the UBP scoring system has not yet been fully validated and developed. Further studies may offer models generating predictions with a more test–retest reliability. Thirdly, we followed the pregnancy outcome for 16 days after insemination. Longer-term follow-up, preferentially to the birth time, may provide more details; however, this needs a large number of cases being studied to get an acceptable number of patients ending up with healthy live birth. Finally, one may consider evaluating the UBP scoring system predictive value in other ART procedures, such as in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), etc., and compare them to each other.

Conclusion

According to the results of this study, UBP parameters and total UBP score are not significant predictors of success rate in patients undergoing IUI treatment; and literature shows a lot of controversies surrounding their predictability for post-ARTs pregnancy outcome. The impact of infertility on couples’ psychological well-being and health care systems is enormous, and a repeatable and externally validated predictive model is a dire necessity for consulting anxious infertile couples about ART success rate with a decent confidence. The current UBP scoring system seems to need more data for external validation, or it might require modifications before implementation, as it may cause false reassurance.

Abbreviations

ART

Assisted Reproductive Technology

B-hCG

Beta-Human Chorionic Gonadotropin

EBF

Endometrial Blood Flow

EMP

Endometrial Pattern

EMT

Endometrial Thickness

IUI

Intrauterine Insemination

MBF

Myometrial Blood Flow

MCF

Myometrial Contraction Frequency

OF

Ovarian Follicle

PI

Pulsatility Index

TVS

Transvaginal Ultrasonography

UA-PI

Pulsatility Index of Uterine Artery

UBP

Uterine Biophysical Profile

Declarations

Funding

Not applicable.

Conflict of interest

The authors declare no conflicts of interest.

Ethics approval and consent to participate

This work has been approved by the Kermanshah University of Medical Science (KUMS) Ethical Committee Board. Informed consents were obtained from all participants.

Consent to publication

Not applicable.

Availability of data and material

The datasets used and analysed during the current study are available from the corresponding author on reasonable request.

Authors’ contributions

NF, TF and JA provided direction and guidance throughout the preparation of this manuscript. NF, PBK and ML collected the data. NF, PBK and JA analyzed and interpreted data and drafted the manuscript. All authors reviewed the manuscript and made significant revisions and approved the final version of the manuscript draft.