Uterine size and volume are associated with a higher clinical pregnancy rate in patients undergoing assisted reproduction technology: A longitudinal study (A STROBE-compliant article)

Growth hormone therapy is associated with improved uterine dimensions in girls with Turner syndrome prior to oestrogen replacement

BACKGROUND

Adult women with Turner syndrome (TS) have high rates of miscarriage, presumably due to the abnormal size and shape of the uterus. There is a paucity of data regarding the determinants of uterine volume (UtVol) in young girls with TS before the initiation of oestrogen replacement therapy (ERT).

METHODS

We performed a cross-sectional study on premenarchal girls with TS, aged 5-15 years, pubertal stage B1-B3, not having received ERT (n = 73) and 50 age-matched healthy controls. Anthropometric parameters and a history of growth hormone (GH) therapy (≥1 year) were noted. Uterine length (UtL), UtVol, and mean-ovarian-volume (MOV) standard-deviation scores (SDS) were determined from transabdominal ultrasonography data.

RESULTS

Girls with TS had lower median UtVol-SDS (-1.07 vs. 0.86; p < .001), UtL-SDS (-3.72 vs. -0.41; p < .001) and MOV-SDS (-5.53 vs. 1.96; p < .001) compared to age-matched controls. Among TS girls, recipients of GH (n = 38) had higher UtVol-SDS (-0.63 vs. -1.39; p = .0001), UtL-SDS (-1.73 vs. -6.49; p < .0001) but similar MOV-SDS compared to nonrecipients (n = 35). Those with normal uterine volume for age (NUVA, n = 29) had earlier initiation (7.8 vs. 9.3 years; p = .03) and a longer duration of GH (3.71 vs. 2.14 years; p = .002) than those with low UtVol for age (n = 44). UtVol-SDS correlated with duration of GH (ρ = 0.411, p = .01) and negatively with age at GH initiation (ρ = -0.479, p = .003). In a model adjusted for pubertal status, karyotype and height-SDS, GH use could independently predict having NUVA (odds ratio: 5.09, confidence interval: 1.63-15.94, p = .005).

CONCLUSION

GH therapy has a stimulatory effect on uterine dimensions in pre-and peripubertal girls with TS. Earlier initiation and longer duration of GH is important in TS girls before ERT.

Development and validation of a nomogram for predicting ongoing pregnancy in single vitrified-warmed blastocyst embryo transfer cycles

Introduction

The global adoption of the "freeze-all strategy" has led to a continuous increase in utilization of single vitrified-warmed blastocyst embryo transfer (SVBT) owing to its clinical effectiveness. Accurate prediction of clinical pregnancy is crucial from a patient-centered perspective. However, this remains challenging, with inherent limitations due to the absence of precise and user-friendly prediction tools. Thus, this study primarily aimed to develop and assess a nomogram based on quantitative clinical data to optimize the efficacy of personalized prognosis assessment.

Materials and methods

We conducted a retrospective cohort analysis of ongoing pregnancy data from 658 patients with infertility who underwent SVBT at our center between October 17, 2017, and December 18, 2021. Patients were randomly assigned to the training (n=461) or validation (n=197) cohort for nomogram development and testing, respectively. A nomogram was constructed using the results of the multivariable logistic regression (MLR), which included clinical covariates that were assessed for their association with ongoing pregnancy.

Results

The MLR identified eight significant variables that independently predicted ongoing pregnancy outcomes in the study population. These predictors encompassed maternal physiology, including maternal age at oocyte retrieval and serum anti-Müllerian hormone levels; uterine factors, such as adenomyosis; and various embryo assessment parameters, including the number of fertilized embryos, blastocyst morphology, blastulation day, blastocyst re-expansion speed, and presence of embryo string. The area under the receiver operating characteristic curve in our prediction model was 0.675 (95% confidence interval [CI], 0.622-0.729) and 0.656 (95% CI, 0.573-0.739) in the training and validation cohorts, respectively, indicating good discrimination performance in both cohorts.

Conclusions

Our individualized nomogram is a practical and user-friendly tool that can provide accurate and useful SVBT information for patients and clinicians. By offering this model to patients, clinical stakeholders can alleviate uncertainty and confusion about fertility treatment options and enhance patients' confidence in making informed decisions.

Differences in the anatomical structure of the uterus between fertile and infertile individuals

Infertility affects a significant portion of the reproductive population and is caused by structural and hormonal factors. The prevalence of congenital uterine anomalies is 3%-4%, with the most common anomaly being septate uterus. However, further research is needed to determine whether these anomalies can cause infertility. In this study, we compared the morphometric parameters of the uterus of fertile and infertile individuals. Based on the data obtained, we aimed to determine the parameters to be evaluated for fertility prediction and to investigate the effect of uterine septum on fertility. The uteruses of 55 infertile and 80 fertile individuals between the age range of 20-45 years were analyzed retrospectively using magnetic resonance images. Infertile individuals were categorized into two groups according to the reasons for infertility: Group I, which included women with congenital uterine anomalies (septate uterus), and Group II, which included women with tubal and male factors. Group III comprised fertile individuals. Uterine length (UL), uterine body length (UbL), cervical length (CxL), uterine cavity length (UcL), anteroposterior diameter (APD), transverse diameter (TD), fundal thickness (FT), and ostial distance (OD) were measured. The uterine positions were examined. The data of uterine variables were evaluated statistically according to age and groups. The mean ages of individuals in Groups I, II, and III were 29.88 ± 6.69, 29.21 ± 4.59, and 27.45 ± 5.43 years, respectively. Significant differences were observed between the groups in terms of UL, UbL, CxL, UcL, APD, FT, and OD variables (p < 0.05), except for TD (p > 0.05). We observed that UL, UcL, length/width ratio, and APD parameters are important factors that influence fertility. Evaluating these parameters before septum resection would be useful in predicting the contribution of this surgical operation to fertility.

Complementary and Alternative Medicine Use Among Women with Symptomatic Uterine Fibroids

Objective: The aim of this study is to examine complementary and alternative medicine (CAM) use among women with symptomatic uterine fibroids in the United States. Materials and Methods: In this cross-sectional analysis of baseline data from a multicenter, prospective cohort study of premenopausal women undergoing surgery for symptomatic fibroids and who enrolled in the Uterine Leiomyoma Treatment with Radiofrequency Ablation study from 2017 to 2019, we contrast women indicating use of at least one CAM modality specifically for fibroid symptoms against women using CAM for other reasons and CAM nonusers. Multivariable logistic regression models were performed to identify participant characteristics independently associated with CAM use for fibroids. Results: Among 204 women, 55% were Black/African American and the mean age was 42 (standard deviation 6.6) years. CAM use was common (67%), with 42% (95% confidence interval [CI]: 35%-49%) reporting use of CAM specifically to treat fibroid symptoms. Most commonly, CAM treatments used for fibroids were diet (62%) and herbs (52%), while CAM treatments for other reasons were exercise (80%) and massage (43%). On average, each participant who reported CAM use utilized three different types of CAM modalities. In a multivariable model, participants were more likely to use CAM for fibroids if they had pelvic pressure (odds ratio [OR] 2.50, 95% CI: 1.07-5.87, p = 0.04), a body-mass index lower than average (OR 0.76, 95% CI: 0.60-0.97, p = 0.03), and a lower health-related quality of life score (OR 0.61, 95% CI: 0.46-0.81, p = 0.001). Conclusions: In this diverse sample of women with symptomatic fibroids, CAM use was highly prevalent. Our findings highlight the need for providers to query patients about CAM use and understand the role of CAM in fibroid management. ClinicalTrials.gov Identifier: NCT02100904.

Short Communication: Influence of estrus activity and reproductive tract size and position scores on fertility in Bos indicus and Bos taurus suckled beef cows

The primary objective of this study was to determine if estrus activity and reproductive tract size and position score (SPS) are associated with pregnancy outcomes in Bos indicus (Nelore) and Bos taurus (Angus) beef cows. In study 1, multiparous Nelore cows (n = 1,280) were artificially inseminated at a fixed time (FTAI, day 0) using an estradiol and progesterone (P4)-based estrus synchronization protocol. In study 2, multiparous Angus cows (n = 764) were artificially inseminated at a fixed time (FTAI, day 0) using a gonadotropin-releasing hormone and P4-based estrus synchronization protocol. Estrus activity was assessed using Estrotect heat detector patches and scored on day 0 using the following scoring system: 0 (patch was lost, most likely due to repeated mounting), 1 (<25% activation), 2 (≥25%, <50% activation), 3 (≥50%, <75% activation), or 4 (>75% activation) where patch scores of 1 and 2 signified no or limited estrus activity, whereas scores of 0, 3, and 4 had increased estrus activity. Reproductive tract SPS were assigned on day 0 as SPS1: small and compact resting within the pelvic cavity; SPS2: intermediate, resting partially outside the pelvic cavity; and SPS3: larger and resting outside the pelvic cavity. Pregnancy diagnosis was performed by ultrasound on day 30 and 100 after FTAI. Cows were determined as undergoing pregnancy loss if a viable embryo with heartbeat was detected at day 30 but was no longer present at day 100. Pregnancy rate at day 30 was influenced by estrus activity and SPS in both Nelore (P = 0.004) and Angus (P = 0.009) cows. Specifically, cows with smaller reproductive tracts (SPS1) had greater (P < 0.001) pregnancy rate when estrus was expressed before FTAI. There was no effect of estrus activity nor reproductive tract size on pregnancy loss between day 30 and 100 for both breeds. In summary, estrus activity before FTAI may influence reproductive outcomes differently depending on size and position of the reproductive tract at time of breeding.

Three-dimensional measurement and analysis of morphological parameters of the uterus in infertile women

BACKGROUND

To determine differences in endometrial cavity anteroposterior diameter, thickness, volume, and diameter lines of uterine body and thickness, and volume of upper, middle, and lower regions of the endometrium in infertile women using a new method for three-dimensional (3D) reconstruction based on two-dimensional (2D) ultrasound images.

METHODS

This retrospective cross-sectional study included a total of 81 infertile women, who underwent 2D ultrasound standard examination. We created 3D models of the uterine body, endometrial cavity, and endometrium based on 2D ultrasound images. The parameters that were measured and analyzed in a 3D plane included volume and diameter lines of endometrial cavity, surface area, thickness, volume, and diameter lines of uterine body, and surface area, thickness, and volume of upper, middle, and lower region of the endometrium. These parameters were used for comparisons between normal and arcuate uterus, between non-pregnant and pregnant infertile women, and between nulliparous and multiparous infertile women. The differences between the different regions of the endometrium and the correlations between age and the parameters were also determined in this study.

RESULTS

Endometrial cavity length, and middle and lower regions of the endometrial volume in the normal uterus were 39.63±7.61 mm, 1,307.92±1,034.40 mm3, and 653.98±460.41 mm3, respectively. For arcuate uterus, these parameters were 32.96±4.69 mm, 539.89±298.94 mm3, and 347.90±129.61 mm3, respectively. The parameters were significantly higher in normal uterus compared with arcuate uterus (P=0.000, 0.001, and 0.006, respectively). Upper, middle, and lower regions of endometrial thickness in normal uterus were 7.79±3.26, 8.18±3.33, and 6.41±2.60 mm, respectively. Both upper and middle regions of endometrial thickness were significantly greater than the lower regions of endometrial thickness with P=0.009 and P=0.001, respectively. Correlation analysis revealed that age positively correlated with volume of upper endometrial regions (r=0.274, P=0.028).

CONCLUSIONS

This study provides references for the volume and thickness of the endometrium in the different anatomical regions of normal and arcuate uterus. Age mainly affects the upper region of the endometrium. The 3D measurement provides a precise way to quantify the morphological parameters of gynecological diseases.

Extrinsic Adenomyosis Is Associated With Postoperative Recurrence of Ovarian Endometrioma

Objective: To determine whether endometrioma recurrence is closely related to the presence of extrinsic adenomyosis, which was demonstrated by magnetic resonance imaging (MRI). Design: Observational crosssectional study involving patients with the recurrence of ovarian endometrioma (OMA). Correlations of endometrioma recurrence and adenomyosis subtypes shown by MRI were analyzed. Method: Between January 2018 and December 2020, a total of 233 patients with recurrence of OMA after ovarian cystectomy were administered for surgery at our institution. All patients were divided into subtype II (Group A), subtype I+IV (Group B), and nonadenomyosis (Group C) groups at preoperative MRI imaging. The correlations of endometrioma recurrence with clinical features, imaging appearance, and surgical findings were retrospectively analyzed. Results: We found 112 (48.07%) patients of endometrioma recurrence combined with subtype II adenomyosis, 8 (3.43%) subtype I adenomyosis, 47 (20.17%) subtype IV adenomyosis, 66 (28.32%) nonadenomyosis. The mean time of OMA recurrence (44.28 ± 8.37, vs. 63.96 ± 10.28, vs. 69.36 ± 9.34 mon), rate of pain symptoms (85.71, vs. 69.10, vs. 18.18%), and primary infertility (31.25, vs. 14.55, vs. 10.77%) were higher in Group A. Uterine volume (257.37± 42.61, vs. 203.14 ± 33.52, vs. 100.85 ± 26.67 cm³), and mean OMA size (4.97 ± 2.25, vs. 4.36 ± 2.38, vs. 4.46 ± 2.70 cm) were significantly larger in Group A. The rate of DIE (83.93, vs. 45.45, vs. 40.91%), the number of DIE (3.6 ± 1.8 vs. 2.3 ± 1.5 vs. 2.2 ± 1.3), the mean total revised American Society for Reproductive Medicine score (rASRM, 103.14 ± 23.89 vs. 74.23 ± 16.72 vs. 36.51 ± 14.23) were significantly higher in Group A. After a multiple logistic regression analysis, extrinsic adenomyosis (OR 2.5, 95% CI 1.2-3.4), DIE lesions (OR 2.1, 95% CI 1.4-2.8), and primary infertility (OR 1.8, 95% CI 1.3-4.3) were significantly associated with early recurrence (in 3-year) of OMA. Conclusions: Extrinsic adenomyosis was associated with postoperative recurrence of OMA. In addition, a pathogenic link between extrinsic adenomyosis and pelvic endometriosis needs to be clarified.

The density of endometrial glandular openings: a novel variable to predict the live birth rate in patients with intrauterine adhesions following hysteroscopic adhesiolysis

STUDY QUESTION

Can the density of endometrial glandular openings (DEGO) be a reliable and simple new variable in the prediction of live birth after hysteroscopic adhesiolysis?

SUMMARY ANSWER

The DEGO grade at follow-up hysteroscopy outperforms American Fertility Society (AFS) score in predicting the live birth rate after hysteroscopic adhesiolysis for patients with intrauterine adhesions (IUAs).

WHAT IS KNOWN ALREADY

Several methods, such as endometrial thickness and AFS score, have been proposed for predicting the live birth rate in patients with IUAs who undergo hysteroscopic adhesiolysis.

STUDY DESIGN, SIZE, DURATION

A test cohort of 457 patients with IUAs who underwent hysteroscopic adhesiolysis and had satisfactory follow-up hysteroscopy videos were retrospectively enrolled between January 2016 and January 2017. A validation cohort comprising 285 IUA patients was prospectively enrolled from March 2018 to August 2018.

PARTICIPANTS/MATERIALS, SETTING, METHODS

An automated counting software tested the follow-up hysteroscopy videos to calculate the DEGO grade of all the 742 patients with IUAs after hysteroscopic adhesiolysis. The AFS score for each patient was also calculated at the same follow-up hysteroscopy. Logistic regression analysis was performed to develop prediction models to predict the live birth rate following hysteroscopic adhesiolysis. The performance of each of these prediction models was compared by calculating the AUC.

MAIN RESULTS AND THE ROLE OF CHANCE

In the test cohort (n = 457), 231 patients had a live birth, but 226 patients failed. In the validation cohort (n = 285), 117 patients had a live birth, while 168 patients did not. The logistic regression analysis revealed that both the DEGO grade and AFS score at follow-up hysteroscopy were closely correlated with the live birth rate in patients with IUAs (P = 0). The AUCs of AFS score and DEGO grade in the test cohort were 0.7112 and 0.8498, respectively (P < 0.0001). The AUCs of AFS score and DEGO grade in the prospective external validation cohort were 0.6937 and 0.8248, respectively (P < 0.0001).

LIMITATIONS, REASONS FOR CAUTION

Further well-designed prospective clinical studies with a multicentric larger sample size should be needed to confirm the feasibility and efficacy of DEGO.

WIDER IMPLICATIONS OF THE FINDINGS

The DEGO grade is an accurate predictor factor of live birth rate in patients with IUAs following hysteroscopic adhesiolysis and can represent in the future an important and promising tool for assessing obstetric outcomes in IUAs.

STUDY FUNDING/COMPETING INTEREST(S)

This study is supported by National Key Research and Development Program of China (Grant No. 2018YFC1004800), Natural Science Foundation of China (Grant No. 81671492), Natural Science Foundation of Hunan (Grant No. 2020JJ5859). B.G. is supported by Chinese Scholarship Council (File number. 201806370178). The authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A

Effect of uterine dimensions on live birth rates after single embryo transfer in infertile women

RESEARCH QUESTION

Do uterine size parameters measured by baseline transvaginal ultrasound predict live birth after single embryo transfer (SET) of a high-quality blastocyst?

DESIGN

Retrospective cohort study including women undergoing their first SET between August 2010 and March 2014 at a large university hospital reproductive centre. The effects of baseline uterine dimensions on live birth rate (LBR) were analysed while controlling for confounding effects.

RESULTS

A total of 437 nulliparous and 70 parous women were included. The nulliparous group had lower body mass index (BMI) (24.4 ± 5.1 versus 25.9 ± 4.5 kg/m²; P = 0.015) and a higher number of fibroids (0.4 ± 1.0 versus 0.2 ± 0.5; P = 0.005) than the parous group. While controlling for confounding effects, none of the uterine parameters appeared to be a significant predictor of LBR among nulliparous and parous women (P > 0.05 in all cases). A subsequent analysis of endometrial length was done, whereby the endometrial lengths were divided into quartiles (20.0-32.2 mm; 32.3-36.5 mm; 36.6-40.0 mm; 40.1-54.0 mm). After controlling for confounders, the shortest quartile in the nulliparous group had a significantly lower LBR (P = 0.02) than the other groups. Receiver operating characteristic curves suggested that endometrial cavity length and cervical length did not aid clinically.

CONCLUSION

Uterine parameters do not have a clinically useful impact on LBR after SET of a blastocyst in infertile women. The use of baseline endometrial length to predict live birth is no better than chance, while cervical length only predicts failure to live birth.

Effect of Dosage of 17ß-Estradiol on Uterine Growth in Turner Syndrome-A Randomized Controlled Clinical Pilot Trial

CONTEXT

Most Turner syndrome (TS) girls need exogenous estrogen treatment to induce puberty and normal uterine growth. After puberty, the optimal estrogen treatment protocol has not been determined.

OBJECTIVE

To compare 2 doses of oral 17ß-estradiol on uterine size.

DESIGN

A double-blind, 5-year randomized controlled clinical trial.

SETTING

Ambulatory care.

PARTICIPANTS

Twenty young TS women (19.2 ± 2.5 years, range 16.0-24.9) participated. Sixteen patients completed the study. No patients withdrew due to adverse effects.

INTERVENTION

The lower dose (LD) group took 2 mg 17ß-estradiol/d orally and placebo. The higher dose (HD) group took 4 mg 17ß-estradiol/d orally.

MAIN OUTCOME MEASURE(S)

Uterine volume evaluated by transabdominal ultrasound yearly.

RESULTS

Uterine size increased significantly more in the HD group compared with the LD group (P = 0.038), with a gain in uterine volume within the first 3 years of treatment of 19.6 mL (95% confidence interval [CI] = 4.0-19.0) in the HD group compared with 11.5 mL (95% CI = 11.2-27.9) in the LD group. The difference in 3-year gain was 8.1 mL (95% CI = 0.7-15.9). At the last visit, there were no significant differences in uterine volume between the groups.

CONCLUSION

HD oral 17ß-estradiol induces a steeper increase in uterine volume within the first years of treatment compared with the LD. However, the uterine growth potential seems to be the same in most young TS women making the duration of treatment equally significant as estrogen dose, although a few TS women did not experience sufficient uterine growth on 2 mg of estradiol.

CLINICALTRIALS.GOV

NCT00134745Abbreviations: BMI, body mass index; BSA, body surface area; DHEAS, dihydroepiandrosteronesulfate; HD, higher dose; HRT, hormone replacement therapy; LD, lower dose; TS, Turner syndrome; US, ultrasound.

Logistic regression analyses of factors affecting fertility of intrauterine adhesions patients

Background

Intrauterine adhesion (IUA) prevalence is difficult to measure, but appears to have increased over the last few decades. The reproductive outcomes following hysteroscopic adhesiolysis (HA) for moderate-severe IUAs were unsatisfactory, and few studies have analyzed the clinical characteristics pre-, intra- and post-HA to determine the main risk factors for infertility in patients with IUAs.

Methods

This retrospective observational study included 406 patients, desiring fertility, who had undergone HA between January 1st, 2016 to May 31st, 2017, and had moderate-to-severe IUA [5-12 on the American Fertility Society (AFS) classification scale]. Logistic regression was performed to analyze the data of the clinical characteristics associated with IUA.

Results

A total of 406 IUA patients were initially collected. Twenty-six [26] were lost during follow-up or excluded by other criteria; 380 were included in the study with a follow-up period ranging from 2 to 3 years. There were 215 patients (56.6%) that became pregnant, of whom 18 spontaneously miscarried, 5 birthed prematurely (31-36 gestational weeks), 182 delivered at term, and 10 were pregnant at the end of the study. A bivariate and binary logistic regression analysis showed that an age of >30 years, cohesive IUA, lack of increased menstrual volume, and more than 2 times undergoing HA procedure were the risk factors for infertility in IUA patients (P<0.05).

Conclusions

Age, severity of IUA, increased menstrual volume, and HA procedures were the dominant factors affecting reproductive outcomes and may be regarded as potential predictors for evaluating IUA prognosis.

Cold scissors ploughing technique in hysteroscopic adhesiolysis: a comparative study

Background

Intrauterine adhesions (IUAs) can be dissected using hysteroscopic scissors (cold scissors) or other methods, but there is no consensus on which hysteroscopic method is preferable. There is also no consensus on the method of how to deal with the scar tissue on the surface of the intrauterine cavity.

Methods

From January 2016 to October 2017, 179 patients who had HA met the enrollment criteria (see the text below), and their data were analyzed retrospectively. In addition, all patients were divided into three groups according to the surgical techniques used. The groups were the ploughing group (PG) (using cold scissors to dissect the adhesion and cut the scar tissue using a ploughing technique) (n=81), the traditional group (TG) (using cold scissors to dissect the adhesion, but not deal with the scar tissue) (n=42), and the electrosurgical group (EG) (using a resectoscope to dissect the adhesion with an energy L-hook electrode, and not deal with the scar tissue) (n=56). Safety (surgical complications), feasibility (surgical technique replacement rate), and postoperative efficacy (reduction of AFS score, pregnancy, and live birth rate), were each evaluated between groups.

Results

No statistically significant differences between the groups were observed in basic preoperative information (P>0.05), while there were significant differences between PG and TG, as well as PG and EG in postoperative AFS scores (PG vs. TG: P=0.007; PG vs. EG: P<0.001) and pregnancy outcome (PG vs. TG: P=0.039; PG vs. EG: P<0.001). No patients had surgical complications such as uterine perforations, moderate or severe fluid overload, heavy uterine bleeding, nor any surgical technique replacements (for example, transfer to use a resectoscope).

Conclusions

Cold scissors ploughing technique in HA is effective, feasible, and safe, and thus worthy of further study.

Uterine size and volume are associated with higher live birth rate in patients undergoing assisted reproduction technology: A prospective cohort study

To investigate how uterine size and volume are associated with live birth rate in patients undergoing assisted reproduction technology.This prospective cohort study was conducted at the Reproductive Medicine Centre from January 2010 to May 2017. Multivariate binary logistic regression was used to evaluate the relations between uterine size, total volume, and live birth outcomes, after they were adjusted for the main influencing factors.A total of 7320 women of clinical pregnancy were enrolled. Compared with uterine lengths of 50 to 59 mm (referent), women with uterine lengths ≥60 mm had a lower live birth rate (RR = 1.541). Compared with uterine widths of ≥50 mm (referent), women with uterine widths <30 mm had a lower live birth rate (RR = 1.430). Compared with uterine anteroposterior diameters of <30 mm (referent), women with uterine anteroposterior diameters ≥50 mm had a lower live birth rate (RR = 1.636). Compared with uterine volumes of 30 to 49 mL (referent), women with volumes <30 mL and ≥70 mL had lower live birth rates (RR = 1.368 and 1.742, respectively).Our findings indicate that uterine sizes and volumes that were too large or too small reduced the live birth rate.