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Knowing the predictors of pregnancy outcomes in patients with recurrent spontaneous abortion (RSA) is extremely critical. Accordingly, we aimed to determine the effects of the difference between mean gestational sac diameter and crown-rump length (mGSD-CRL) on the pregnancy outcomes in patients with RSA at 6–10 gestational weeks, as well as to explore its significance in predicting the pregnancy outcomes of patients with RSA. This retrospective cohort study included 256 pregnant women at 6–10 weeks of gestation and with RSA who had visited our hospital from January 2020 to March 2023. The patients were allocated to three groups based on the mGSD-CRL difference: Group A: mGSD-CRL ≤ 10 mm, Group B: 10 mm < mGSD-CRL ≤ 15 mm, and Group C: mGSD-CRL > 15 mm. The pregnancy failure rate in Group A was 22%, which was higher than those that in Group B (5.5%) and Group C (9.4%), with statistically significant differences ( P  < 0.05). Binary logistic regression analysis revealed that the mGSD (odd ratio [OR] = 1.14, 95% confidence interval [CI] = 1.06–1.23, P  = 0.001), the CRL (OR = 1.16, 95% CI = 1.05–1.28, P  = 0.004), and mGSD-CRL (OR = 1.12, 95% CI = 1.01–1.24, P  = 0.026) were independent risk factors affecting the pregnancy outcome of patients with RSA. However, the uterine artery peak systolic value to end-diastolic value (UtA-S/D), D-dimer (DD), adenosine diphosphate (ADP), and arachidonic acid (AA) were not related ( P  > 0.05). The area under the receiver operator characteristic (ROC) curve of mGSD-CRL at 6–10 weeks of pregnancy was 0.566, with a cutoff value of 9.50 mm. The sensitivity and specificity were 90% and 36%, respectively. Compared with their prediction value, the combined prediction of mGSD-CRL, mGSD, and CRL exhibited a higher value (AUC = 0.718) in predicting pregnancy outcomes. A weak negative correlation was detected between ADP and mGSD-CRL difference ( r  = − 0.165, P  = 0.025). In patients with RSA, mGSD-CRL acts as an independent risk factor affecting pregnancy outcomes, thereby effectively predicting the early pregnancy outcomes of patients with RSA. Thus, a low mGSD-CRL difference signifies the heightened probability of miscarriage, thereby urgently requiring clinicians to pay timely attention. Trial registration: The study is registered at ClinincalTrails.gov (Trial registration number: NCT06081556, October 13, 2023).

Background This study aimed to develop a new ultrasonographic dating formula to estimate gestational age (GA) based on fetal crown–rump length (CRL) in a Chinese population, evaluate model accuracy and compare its performance with established dating formulas. Methods A prospective, multicenter study was conducted across mainland China. Participants included healthy, low-risk women with spontaneously conceived singleton pregnancies and a regular menstrual cycle in the preceding year. Ultrasonography was performed between 11 and 14 weeks of gestation, with GA determined based on the last menstrual period. Participants were randomly assigned to a development or validation cohort in a 7:3 ratio. A best-fit regression model was constructed for GA estimation based on CRL in the development cohort. For validation, mean differences between the new estimated GA and menstrual age were calculated and compared with those obtained using five established CRL-based dating formulas in the validation cohort. All participants were followed through to delivery. Results The study recruited 4,710 women with singleton pregnancies, with 3,297 in the development cohort and 1,413 women in the validation cohort. The mean and standard deviation values of CRL changed linearly with GA during 11–14 weeks. CRL demonstrated a linear relationship with GA between 11 and 14 weeks, yielding the regression equation GA = 59.590085 + 0.458539×CRL (R 2  = 0.8042). The mean difference between estimated GA and menstrual age was 0.32 days (95% confidence interval 0.17–0.46), demonstrating a smaller error compared with those obtained from the five widely used CRL dating formulas. Conclusions We derived a CRL-based dating formula applicable to naturally conceived pregnancies at 11–14 weeks. This new formula exhibits small residuals, providing a more accurate alternative to existing CRL-based dating formulas.

Introduction The inaccuracy of late pregnancy dating is often discussed, and the impact on diagnosis of fetal growth restriction is a concern. However, the magnitude and direction of this effect has not previously been demonstrated. In this study, we aimed to investigate the effect of late pregnancy dating by head circumference on the detection of late onset growth restriction, compared to first trimester crown‐rump length dating. Material and methods This was a cohort study of 14 013 pregnancies receiving obstetric care at a tertiary center over a three‐year period. Universal scans were performed at 12 weeks, including crown‐rump length; at 20 weeks including fetal biometry; and at 36 weeks, where biometry, umbilical artery doppler and cerebroplacental ratio were used to determine the incidence of fetal growth restriction according to the Delphi consensus. For the entire cohort, the gestational age was first calculated using T1 dating; and was then recalculated using head circumference at 20 weeks (T2 dating); and at 36 weeks (T3 dating). The incidence of fetal growth restriction following T2 and T3 dating was compared to T1 dating using four‐by‐four sensitivity tables. Results When the cohort was redated from T1 to T2, the median gestation at delivery changed from 40 + 0 to 40 + 2 weeks (p < 0.001). When the cohort was redated from T1 to T3, the median gestation at delivery changed from 40 + 0 to 40 + 3 weeks (p < 0.001). T2 dating resulted in fetal growth restriction sensitivity of 80.2% with positive predictive value of 78.8% compared to T1 dating. T3 dating resulted in sensitivity of 8.6% and positive predictive value of 27.7%, respectively. The sensitivity of abnormal CPR remained high despite T2 and T3 redating; 98.0% and 89.4%, respectively. Conclusions Although dating at 11–14 weeks is recommended, late pregnancy dating is sometimes inevitable, and this can prolong the estimated due date by an average of two to three days. One in five pregnancies which would be classified as growth restricted if the pregnancy was dated in the first trimester, will be reclassified as nongrowth restricted following dating at 20 weeks, whereas nine out of 10 pregnancies will be reclassified as non‐growth restricted with 36‐week dating. Dating of pregnancies by head circumference in the second or third trimester can lead to underdiagnosis of fetal growth restriction compared with first trimester dating using crown‐rump‐length. However, false positives for fetal growth restriction diagnosis may also occur. The incidence of abnormal cerebroplacental ratio is least affected by late pregnancy dating.

Infant undernutrition, defined by length‐ and weight‐based indices, is common in low‐ and middle‐income countries (LMICs), but corresponding deficits in head size have received less attention. In a cohort of term newborns in Dhaka, Bangladesh, we compared the severity of deficits (vs. World Health Organization Growth Standards) in head circumference (HC), length and weight at birth and every 3 months until 2 years of age (n range across timepoints: 843–920). We estimated the mean and 25th, 50th and 75th percentiles of HC‐, length‐ and weight‐for‐age z‐scores (HCZ, LAZ and WAZ, respectively). Differences between HCZ and LAZ (or WAZ) were analyzed using paired t tests and quantile regression. We also derived HCZ using height‐age instead of chronological age at 3–24 months. Mean HCZ was significantly higher than mean LAZ and WAZ at birth, but HCZ was significantly lower than LAZ at 6, 9 and 12 months and the HCZ and LAZ deficits were similar from 15 to 24 months. Mean HCZ was lower than WAZ at all ages beyond birth. Patterns were broadly consistent at the 25th, 50th and 75th percentiles. The HCZ deficit remained evident when HC was standardized using height‐age at all ages beyond birth, indicating HC was reduced relative to body size. In conclusion, among term‐born children in Dhaka, HCs were smaller than international standards at all ages up to 2 years, and there was no evidence of postnatal head sparing. Consideration should be given to routine measurement of HC in population health surveys in LMICs. Term infants in Bangladesh had smaller head circumferences compared to international standards. In the postnatal period (3–24 months of age), average deficits in head circumference were more severe than expected based on body lengths, indicating a lack of head‐sparing in a setting where early childhood undernutrition is widespread. Summary In a Bangladeshi cohort of term infants, average head circumference (HC) z‐scores were closer to international norms than corresponding length and weight z‐scores at birth, suggesting possible foetal head sparing. Postnatal head sparing was not observed among children in Dhaka at any timepoint following birth. At 6, 9 and 12 months of age, the HC distribution was further below the international norm compared to the length and weight distributions. Analyses using height‐age rather than chronological age showed that postnatal HC deficits were more severe than expected given children's average height, at all timepoints following birth. The entire HC distribution was negatively displaced relative to the international standard at all ages, indicating that the head size deficit is a whole‐population condition, analogous to linear growth faltering. HC, like length and weight, should be considered for routine monitoring in LMIC settings where early childhood undernutrition is common.

Background Selective intrauterine foetal growth restriction (sIUGR) and twin–twin transfusion syndrome (TTTS) are common complications in Monochorionic diamniotic (MCDA) twin pregnancies. Timely and accurate diagnosis and intervention are essential to improve perinatal outcomes. The purpose of this study was to determine the value of differences in crown - rump lengths (CRL) and nuchal translucency (NT) and evaluate the significance of differences in embryo length in predicting the occurrence of sIUGR and TTTS. Methods This research is a retrospective study that includes cases of MCDA twins diagnosed via ultrasound in the Obstetrics Department of Shandong Provincial Hospital Affiliated to Shandong University from January 2017 to March 2024. These cases were categorized into sIUGR group, TTTS group, TTTS with sIUGR group and normal MCDA group, based on the presence of complex twin related complications. For each group, embryo length, CRL and NT measured by ultrasound during the 7–14 week gestation period were respectively recorded. The differences in embryo length, CRL and NT between the normal MCDA twin group and sIUGR group, TTTS group, as well as TTTS with sIUGR group were compared. The Mann‒Whitney U test and the chi‒square test were utilized for the analysis. Furthermore, the receiver operating characteristic (ROC) curve was plotted to conduct further analysis. Results A total of 722 MCDA twins (203 with sIUGR, 158 with TTTS, 55 with TTTS with sIUGR and 306 controls) were included. The difference in the CRL in the sIUGR group (9.43%) was significantly greater than that in the control group (3.30%) ( P  < 0.001). However, no statistically significant difference in NT or embryo length was detected ( P  = 0.271, 0.567). The difference in CRL could not be used to distinguish between sIUGR-type I and sIUGR-type II/III ( P  = 0.35). ROC analysis revealed that the difference in CRL predicted sIUGR with an area under the curve of 0.78; for comparison, the area under the curve for the prediction of TTTS was 0.51. The prediction of sIUGR using the CRL difference threshold of 7.38% had a sensitivity of 80.72% and a specificity of 67%, a positive predictive value (PPV) of 67%, and a negative predictive value (NPV) of 80.72%. Conclusions In MCDA twin pregnancies, the difference in the first-trimester CRL was valuable for predicting the occurrence of sIUGR but was not associated with TTTS. Embryo length and NT did not significantly differ among the groups. Trial registration Not applicable.

Abstract STUDY QUESTION Is first-trimester intrauterine growth different between pregnancies resulting in live births established using fresh or frozen single embryo transfers (ET), and is it related to the embryo stage at the timing of transfer? SUMMARY ANSWER Among pregnancies resulting in live birth, the use of frozen embryo transfer was associated with larger crown–rump length in the first trimester compared with fresh embryo transfer, regardless of the embryo stage at the timing of transfer. WHAT IS KNOWN ALREADY Studies have indicated that singletons born following frozen/thawed ET have a higher likelihood of increased birthweight, in comparison with children born after fresh ET. A few studies have also suggested greater crown–rump length (CRL) in pregnancies after frozen embryo transfer (FET) compared to fresh ET. However, discrepancies exist regarding the intrauterine growth between fresh ET and FET groups, and the knowledge regarding the effect of embryo stage at transfer (cleavage stage vs. blastocyst stage) on the first-trimester growth remains limited. STUDY DESIGN, SIZE, DURATION This prospective cohort study included all single ETs resulting in singleton pregnancies and live births following either FET or fresh ET at an academic reproductive medical center during 2013–2024. PARTICIPANTS/MATERIALS, SETTING, METHODS Among 3445 singleton live births during the study period, 54.3% were after FET, and 62.2% after blastocyst transfer. All underwent an ultrasound scan between 6 and 12 gestational weeks to measure the CRL (mm). Generalized additive models were used to compare the CRL between pregnancies after FET and fresh ET, as well as to investigate associations according to embryo stage at transfer (cleavage stage or blastocyst stage), accounting for multiple confounders. MAIN RESULTS AND THE ROLE OF CHANCE Compared with pregnancies after fresh ET, the CRL in pregnancies after FET was larger after adjusting for gestational age, embryo stage at transfer, parental age, maternal BMI, and smoking status in the first trimester, though the difference was small (β = 0.30 mm, 95% CI: 0.00–0.60, P = 0.053). The difference remained in subgroups defined by the embryo stage at the timing of transfer (β = 0.31 mm, 95% CI: −0.01–0.62, P = 0.055 and β = 0.22 mm, 95% CI: 0.06–0.39, P = 0.008 for cleavage and blastocyst stage, respectively). Normalizing CRL to a reference population conceived naturally from the INTERGROWTH-21(st) project showed that the mean CRL Z-scores in pregnancies after fresh ET and FET were both greater than 0 before day 63, suggesting the CRL in the present study population was larger than that of the non-ART population. LIMITATIONS, REASONS FOR CAUTION The lack of adjustment for other relevant confounders, such as maternal infertility factors, could lead to unmeasured confounding. Additionally, the predominance of fresh embryos in the cleavage-stage ET group limited statistical power. WIDER IMPLICATIONS OF THE FINDINGS A difference in the intrauterine growth of singletons born after frozen and fresh ETs appears early. The effect of FET on the CRL is similar regardless of whether cleavage-stage embryo or blastocyst transfer is used. Thus, the selection of embryo stage at the timing of transfer needs to be informed by other clinical factors. Besides, reliance on CRL for redating pregnancies conceived by assisted reproductive technologies warrants caution as it may overestimate the gestational age and miss potential growth restriction. STUDY FUNDING/COMPETING INTEREST(S) This study was supported by the Swedish Childhood Cancer Fund, Swedish Cancer Society, Radiumhemmets Research Funds, The Swedish Research Council, ALF Grants from Region Stockholm, and Karolinska Institutet research grants to KARW. ARP is supported by fundings of the Beatriz Galindo Program BG23/00015 with further support from FEDER and UE (PID2024-160756OA-I00) both from the Spanish Ministry of Science, Innovation and Universities and KI Research Foundation Grants 2024-2025(2024-02566). The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication. The authors declare no conflicts of interest regarding this work. TRIAL REGISTRATION NUMBER N/A

PurposeThe aim of this study was to determine whether first trimester ultrasound measurements of crown rump length (CRL) and gestational sac diameter (GSD) differ depending on the method of conception among infertile women.MethodInfertile women, ages 21–50 years old, who conceived viable, singleton pregnancies via fresh embryo transfer (ET), frozen ET, non-in vitro fertilization (IVF) fertility treatment, or spontaneously were included in this observational cohort study at an academic fertility practice. Embryonic growth trajectories defined by the CRL and GSD at 6 and 8 weeks’ gestation were analyzed and compared among the methods of conception.ResultsCrown rump length at 6 weeks’ gestation was smaller for conceptions achieved via fresh ET compared with frozen ET in a natural cycle (1.50 vs. 2.50 mm, p = 0.017). Crown rump length was smaller at 8 weeks’ gestation in conceptions achieved via fresh ET compared to frozen ET in a programmed cycle (16.13 vs. 17.02 mm, p = 0.039).ConclusionAmong infertile women, embryo growth may differ between fresh and frozen ET as early as 6 and 8 weeks’ gestation.

Twins achieved through in-vitro fertilisation often undergo a viability ultrasound at 6–9 weeks of gestation. The presence of inter-twin crown-rump length discordance at this stage is not an uncommon finding; however the clinical significance of this is unknown. We analyzed 218 dichorionic twin pregnancies, producing two live fetuses > 24 weeks gestation, to determine whether inter-twin discordance (≥ 85th centile) in the mid-first trimester was associated with birthweight discordance (> 20%), or small for gestational age (< 10th centile). The incidence of birthweight discordance and small for gestational age infants were determined, with no increased risk found for the discordant population. This may provide some reassurance to treating clinicians.

ObjectiveTo evaluate the association between small crown–rump length (CRL) and fetal loss ≤22 weeks in IVF pregnancies.MethodsA retrospective analysis of prospectively collected data at a university-affiliated medical center. All singleton IVF pregnancies within a 5-year period, with a live embryo on first-trimester ultrasound and verified pregnancy outcome were included. Rates of fetal loss ≤22 weeks were compared between pregnancies with a CRL ≤tenth percentile and above the tenth percentile of our population.ResultsOverall, 397 pregnancies met inclusion criteria. Ninety-five percent of CRL measurements were performed at 40–80 gestational days. All live-embryo’s CRL measurements, from 40 to 80 mm, were plotted against expected gestational age (in 5-day clusters), with calculation of the tenth percentile for every gestational age. Total of 64 pregnancies had CRL ≤tenth percentile for gestational age. The rate of fetal loss in this group was significantly higher than in pregnancies with CRL >tenth percentile (17.2 vs. 6.6%, p = 0.005, OR = 2.93, 95% CI 1.2–6.7). In both groups, the majority of fetal losses occurred ≤10 weeks of gestation.ConclusionIn IVF pregnancies with a live embryo, a small CRL at 40–80 days’ gestation may predict fetal loss. Repeated ultrasound should be considered after 1–2 weeks.