Comment déterminer la date de début de grossesse ?

Testing the assumptions of customized intrauterine growth charts using national birth studies

INTRODUCTION

Customized intrauterine growth charts are widely used for growth monitoring and research. They are based on three assumptions: (1) estimated fetal weight (EFW) has a normal distribution with a constant coefficient of variation at all gestational ages; (2) Hadlock's growth curve accurately describes the relation between EFW and gestational ages; (3) associations between EFW and the fetal and maternal characteristics included in the customization model (fetal sex, pre-pregnancy weight, height, parity) are proportional throughout pregnancy. The aim of this study was to test whether these underlying assumptions are verified.

MATERIAL AND METHODS

Data came from (1) the French Longitudinal Study of Children (ELFE) cohort, which recruited births after 32 weeks' gestation in 349 maternity hospitals in France in 2011, and (2) the National Perinatal Survey, which included births from all French maternity hospitals in 2016. The study population included, respectively, 6 920 and 8 969 singleton non-malformed term live births with data on customization characteristics and EFW. We computed the coefficient of variation by gestational age and then modeled the association of gestational age, maternal and fetal characteristics with EFW at the second and third trimester ultrasound and with birthweight using linear regression. To assess the proportionality of the impact of maternal and fetal characteristics, we computed the percent change in weight associated with these characteristics at these three time points.

RESULTS

The coefficient of variation was close to 12% at each gestational age, but EFW was not normally distributed, leading to small but systematic underestimation of fetuses under the 10th percentile. Weights representing the 50th and 10th percentiles based on Hadlock's growth trajectory were lower than observed or predicted weights. Most characteristics more strongly impacted weight at birth than during pregnancy. In the French Longitudinal study of Children (ELFE) cohort, boys were 1.8% (95% confidence interval [CI] 1.3-2.4) heavier than girls in the third trimester, whereas this percentage was 4.6% (95% CI 4.0-5.2) at birth. In the National Perinatal Survey, these percentages were 2.3% (95% CI 1.8-2.8) and 4.3% (95% CI 3.8-4.8).

CONCLUSIONS

These results from two independent sources revealed discrepancies between routine clinical EFW data used for growth monitoring and the customized growth model's assumptions.

World Health Organization fetal growth charts applied in a French birth cohort

OBJECTIVE

To evaluate the applicability of World Health Organization (WHO) fetal growth charts for abdominal circumference (AC), femur length (FL) and estimated fetal weight (EFW) at the second and third trimester ultrasounds in a French birth cohort.

MATERIALS AND METHODS

Using the ELFE cohort of live births after 33 weeks' gestation in France in 2011, we selected 7747 singletons with fetal biometric measurements at the second (20-25 weeks) and third (30-35 weeks) trimester routine ultrasounds. We calculated proportions of fetuses <3rd and <10th percentiles and >90th and >97th percentiles for AC, FL and EFW using WHO charts and two international (Intergrowth and Hadlock) and two national (Salomon and CFEF) charts. Analyses were also carried out in a subsample of 4427 low-risk births.

RESULTS

WHO charts classified 2,3% and 8-10% of fetuses <3rd and <10th percentiles respectively, for AC and FL in the second and third trimesters and EFW in the third trimester. Similarly, about 3 and 10% of fetuses had AC, FL and EFW >97th and >90th percentile in both trimesters. Hadlock and CFEF charts also provided a good fit for third-trimester EFW <10th percentile. For most measures, Intergrowth yielded low proportions <3rd and <10th percentile, and high proportions >90th and >97th percentiles. Proportions were slightly lower for low-risk pregnancies.

CONCLUSION

WHO charts provided a good description of the distribution of French fetal biometric measures. Further research is needed to assess the impact of using WHO charts on obstetrical management and perinatal outcomes.

The impact of optimal dating on the assessment of fetal growth

BACKGROUND

The impact of using the Intergrowth (IG) dating formulae in comparison to the commonly used Robinson dating on the evaluation of biometrics and estimated fetal weight (EFW) has not been evaluated.

METHODS

Nationwide cross-sectional study of routine fetal ultrasound biometry in low-risk pregnant women whose gestational age (GA) had been previously assessed by a first trimester CRL measurement. We compared the CRL-based GA according to the Robinson formula and the IG formula. We evaluated the fetal biometric measurements as well as the EFW taken later in pregnancy depending on the dating formula used. Mean and standard deviation of the Z scores as well as the number and percentage of cases classified as <3rd, < 10th, >90th and > 97th percentile were compared.

RESULTS

Three thousand five hundred twenty-two low-risk women with scans carried out after 18 weeks were included. There were differences of zero, one and 2 days in 642 (18.2%), 2700 (76.7%) and 180 (5%) when GA was estimated based on the Robinson or the IG formula, respectively. The biometry Z scores assessed later in pregnancy were all statistically significantly lower when the Intergrowth-based dating formula was used (p < 10- 4). Likewise, the number and percentage of foetuses classified as <3rd, < 10th, >90th and > 97th percentile demonstrated significant differences. As an example, the proportion of SGA foetuses varied from 3.46 to 4.57% (p = 0.02) and that of LGA foetuses from 17.86 to 13.4% (p < 10- 4).

CONCLUSION

The dating formula used has a quite significant impact on the subsequent evaluation of biometry and EFW. We suggest that the combined and homogeneous use of a recent dating standard, together with prescriptive growth standards established on the same low-risk pregnancies, allows an optimal assessment of fetal growth.

Singleton fetal growth kinetics depend on the mode of conception

OBJECTIVE

To study the impact of in vitro fertilization, with or without intracytoplasmic sperm injection (IVF/ICSI), frozen-embryo transfer (FET), and intrauterine insemination (IUI) on fetal growth kinetics throughout pregnancy and to compare the different modes of conception.

DESIGN

Retrospective cohort study.

SETTING

University.

PATIENT(S)

A total of 560 singleton pregnancies were included (96 IVF, 210 ICSI, 121 FET, and 133 IUI).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

We compared crown-rump length (CRL) at the first trimester (T1: 11-13 weeks of gestation [WG] + 6 days), estimated fetal weight (EFW) at the second (T2: 21-23 WG + 6 days) and third (T3: 31-33 WG + 6 days) trimesters, and birth weight (BW) z-scores with those in the reference curves (Papageorghiou for T1, and Ego M2 for T2, T3, and birth). Multivariate analyses were performed.

RESULT(S)

For T1, the CRL was longer than the reference curve whatever the assisted reproductive technique (ART). For T2, EFW was significantly greater for all groups compared with the reference curve, and for T3 only FET singletons had a greater EFW. ICSI, IVF, and IUI singletons had a significantly lower BW compared with reference curves. For all ART fetuses, growth kinetics differed from T2. Only FET fetuses maintained their significantly above-reference growth values. The proportion of fetuses for which at least one period of growth loss was observed from T2 to birth was higher after IVF, ICSI, and IUI than after FET.

CONCLUSION(S)

For the first time, we have highlighted that fetal growth kinetics differed from T2 depending on the ART protocols used. They could have an impact on trophoblastic invasiveness and might lead to long-term health effects.

Placental volume and other first-trimester outcomes: are there differences between fresh embryo transfer, frozen-thawed embryo transfer and natural conception?

RESEARCH QUESTION

Does mode of conception influence placental volume and other first-trimester outcomes?

DESIGN

This retrospective single-centre case-control study led in Dijon University Hospital included 252 singleton pregnancies (84 IVF with either fresh embryo transfer or frozen-thawed embryo transfer [FET] and 168 natural conceptions). First-trimester placental volume, uterine artery pulsatility index and maternal serum PAPP-A and beta-HCG were measured. Statistical analyses were adjusted for gestational age, the newborn's gender, maternal age, parity, body mass index and smoking status.

RESULTS

Placental volume was significantly greater in the FET group than in the control group (P = 0.043) and fresh embryo transfer (P = 0.023) groups. At birth, fresh embryo transfer newborns were significantly smaller than controls (P = 0.01) and FET newborns (P = 0.008). Postpartum haemorrhage was far more frequent in FET than in controls and fresh embryo transfer group (38.1%, 2.6% and 1.9%, respectively; P < 0.0001). Placental volume positively correlated with PAPP-A, beta-HCG and the newborn's birth weight, and negatively correlated with uterine artery pulsatility index.

CONCLUSIONS

Placental volume and other first-trimester parameters are modified by IVF with fresh embryo transfer and FET compared with natural conception, but with opposite trends. Given the different protocols used for these techniques, hormonal treatment per se may have a major effect on pregnancy outcomes through the modification of placental invasiveness.

A score-based method for quality control of fetal hard palate assessment during routine second-trimester ultrasound examination

INTRODUCTION

When an orofacial cleft lip is discovered, precise characterization of this malformation is necessary, especially the extension of this cleft to the secondary palate. We aimed to develop and evaluate the feasibility/reproducibility of a score-based quality control for the visualization of the fetal hard palate during the second-trimester scan.

MATERIAL AND METHODS

All ultrasound images of fetal hard palate assessed routinely during second-trimester scan were retrospectively retrieved for a 6-month period. One hundred of these images were randomly selected and analyzed by two blinded reviewers, according to a scoring system (0-6 points). Criteria retained in the score were complete palate bone horizontal plate, presence of two pterygoid processes, visible alveolar ridge, and horizontal axis of insonation. A score ≥4 defined images of good quality. Inter- and intra-reviewer reproducibility was assessed.

RESULTS

Inter-reviewer reproducibility was excellent with significant correlation (Pearson coefficient 0.953; P < .0001), global adjusted κ coefficient (0.86, 95% CI 0.79-0.94) and individual criteria adjusted κ coefficient always > 0.8. Rates of images of good quality (score ≥ 4) were 75%-77%, also with excellent agreement (κ coefficient 0.89, 95% CI 0.79-0.99). Intra-reviewer reproducibility retrieved the same results (excellent agreement) except for the axis of insonation (satisfactory agreement).

CONCLUSIONS

This simple image scoring system for the fetal palate is easy, has excellent inter- and intra-reviewer reproducibility and could also help sonographers to correctly identify the palate structure.

Association between amniotic fluid evaluation and fetal biometry: a prospective French "Flash" study

We aimed to study the association between three different methods of assessing the amount of amniotic fluid (subjective method (SM), deepest vertical pocket (DVP) and amniotic fluid index (AFI)) and estimated fetal weight (EFW) (in percentile or Z-score) after adjustment on maternal-fetal parameters. We performed a nationwide cross-sectional study through the French network of obstetric sonographers using the "flash" study method and including low-risk singleton pregnancies from 18-40 weeks. Crude and adjusted odds ratio were computed after stratification upon 2nd and 3rd trimester of pregnancy. 1667 ultrasound scans performed by 65 operators were included. Only Z-score of EFW was significantly associated with SM in both trimesters. For DVP and AFI, Z-score of EFW and male fetal gender was significantly associated with them in 2nd trimester. In the 3rd trimester, both Z-score of EFW and large (LGA) or small for gestational age (SGA) fetus were significantly associated with AFI. and DVP. Overweight woman and class I obesity women were also significantly associated with DVP modification. In conclusion, all three methods of amniotic fluid evaluation are significantly associated to estimated fetal weight. DVP and AFI appeared equivalent except that maternal-fetal factors seemed to have a higher impact in DVP than AFI.

[Report from the CFEF seminar on fetal biometry (June 2017)]

This article reports the conclusions and recommendations resulting from the seminar organized in Paris on June 15, 2017 by the scientific committee of the French College of Fetal Ultrasound (CFEF). The purpose of this meeting was to audit the practices in screening for SGA and IUGR fetuses in France and to discuss ways to improve ultrasound screening. A review of charts, references, standards and common practices was performed. The potential new biometric tools applicable in France were reviewed and analyzed. Eventually, options and recommendations for improvement are proposed.

Assessment of human placental perfusion by intravoxel incoherent motion MR imaging

PURPOSE

To provide functional information on the human placenta, including perfusion, and diffusion, with no contrast agent injection, and to study correlations between intravoxel incoherent motion (IVIM) placental parameters and fetal growth.

MATERIALS AND METHODS

MRI was performed in women undergoing legal termination of pregnancy at 17-34 weeks, including a 4-b-value and 11-b-value DW sequences. The apparent diffusion coefficient (ADC), the restricted diffusion coefficient (D), the pseudoperfusion coefficient (D*), and the perfusion fraction (f) were calculated. Their relationships with gestational age, Z-scores for fetal and placental weight were evaluated by means of regression analysis. Logistic regression analysis was used to assess the ability of IVIM parameters to predict/detect intrauterine growth retardation (SGA).

RESULTS

Fifty-five pregnant women, including nine cases of SGA (16%), were included in the study. The ADC (n = 55) showed a quadratic correlation with gestational age (p < .001) and a linear correlation with the fetal weight Z-score (p = .02). Mean ADC values were significantly different between normally growing and SGA fetuses (2.37 ± 0.25 versus 2.29 ± 0.33 10^-3.mm².s^-1, p=.048). The perfusion fraction f (n = 23) showed a quadratic correlation with gestational age (p = .017) and a linear correlation with the fetal weight Z - score (p = .008). Mean f values differed significantly between normally growing and SGA fetuses (42.55 ± 9.30% versus 27.94 ± 8.76%, p = .002). The receiver operating characteristics (ROC) curve for f to predict SGA was produced (area under the ROC curve = 0.9).

CONCLUSIONS

The observed association between f and fetal weight suggests that fMRI could be suitable for studying placental insufficiency and for identifying risk of SGA.

[How to deal with a fetal head circumference lower than the third percentile?]

The prenatal finding of a head circumference (HC) below the 3rd percentile (p) remains, in the same way as short femur or increased nuchal translucency with normal karyotype, one the most difficult situations for the praticionner in the setting of prenatal diagnosis. Microcephaly is a gateway to possible cerebral pathologies, but the main objective is to identify serious prenatal situations. A standardized HC measurement, the use of adapted reference tools and charts, longitudinal following of cephalic biometrics in high-risk situations, and systematic central nervous system analysis can increase the diagnostic performance of ultrasound which is often disappointing for microcephaly. The early distinction between associated or isolated microcephaly makes it possible to quickly orient the prenatal management and counseling. Fetal MRI and genetic counseling are fundamental in this context, making it possible to specify at best the etiological diagnosis and to provide assistance to the neuropediatrician in the establishment of an often uncertain prognosis. The recent increase in cases of microcephaly concomitant with the epidemic of the ZIKA virus is an additional argument to improve our practices and the daily apprehension of HC<3rd p.

Implementing the INTERGROWTH-21st fetal growth standards in France: a 'flash study' of the College Français d'Echographie Foetale (CFEF)

OBJECTIVES

To assess potential differences in fetal size between the French population and the international population from the INTERGROWTH-21^st (IG-21^st ) Project and to measure the impact of switching to the IG-21^st reference standards for fetal size.

METHODS

This was a nationwide cross-sectional study of fetal ultrasound biometry. Low-risk singleton pregnancies were recruited prospectively within the network of the national French College of Fetal Ultrasound, CFEF, over a 6-week period. Further selection was performed based on the criteria of the IG-21^st Project in order to obtain a comparable population. Head circumference (HC) was used as the main fat-free skeletal measure of growth for comparison of French fetal size with that of the IG-21^st population. The impact of switching to the IG-21^st fetal growth standards was quantified by comparing Z-scores calculated using the IG-21^st standards with those calculated using locally derived reference ranges for HC, abdominal circumference (AC) and femur length (FL).

RESULTS

Following selection, 4858 cases were analyzed. The distribution of HC demonstrated clear similarity between our French population and the IG-21^st population: our observed centile curves closely matched those of IG-21^st and the Z-scores were close to 0 across gestational age. The IG-21^st standards performed as well as did locally derived charts in terms of screening for small-for-gestational age by AC, while they identified significantly fewer small FL values than were expected and than did the locally derived charts.

CONCLUSIONS

Under strict selection criteria, fetal size in France is similar to that of the international population used in the IG-21^st Project. The discrepancies in FL are unlikely to impact on prenatal management. Therefore, switching from locally derived reference ranges to the IG-21^st standards appears to be a safe option. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

[Role of ultrasound in elective abortions]

Ultrasound plays a fundamental role in the management of elective abortions. Although it can improve the quality of post-abortion care, it must not be an obstacle to abortion access. We thus studied the role of ultrasound in pregnancy dating and possible alternatives and analyzed the literature to determine the role of ultrasound in post-abortion follow-up. During an ultrasound scan, the date of conception is estimated by measurement of the crown-rump length (CRL), defined by Robinson, or of the biparietal diameter (BPD), as defined by the French Center for Fetal Ultrasound (CFEF) after 11 weeks of gestation (Robinson and CFEF curves) (grade B). Updated curves have been developed in the INTERGROWTH study. In the context of abortion, the literature recommends the application of a safety margin of 5 days, especially when the CRL and/or BPD measurement indicates a term close to 14 weeks (that is equal or below 80 and 27mm, respectively) (best practice agreement). Accordingly, with the ultrasound measurement reliable to±5 days when its performance meets the relevant criteria, an abortion can take place when the CRL measurement is less than 90mm or the BPD less than 30mm (INTERGROWTH curves) (best practice agreement). While a dating ultrasound should be encouraged, its absence is not an obstacle to scheduling an abortion for women who report that they know the date of their last menstrual period and/or of the at-risk sexual relations and for whom a clinical examination by a healthcare professional is possible (best practice agreement). In cases of intrauterine pregnancy of uncertain viability or of a pregnancy of unknown location, without any particular symptoms, the patient must be able to have a transvaginal ultrasound to increase the precision of the diagnosis (grade B). Various reviews of the literature on post-abortion follow-up indicate that the routine use of ultrasound during instrumental abortions should be avoided (best practice agreement). If it becomes clear immediately after the procedure that the endometrial thickness exceeds 8mm, immediate reaspiration is necessary. Ultrasound examination of the endometrium several days after an instrumental elective abortion does not appear to be relevant (grade B). An analysis of the literature similarly shows that routine ultrasound scans after medical abortions should be avoided. If a transvaginal ultrasound is performed after a medical abortion, it should take place at least two weeks afterwards (best practice agreement). The only aim of an ultrasound examination during follow-up should be to determine whether a gestational sac is present (best practice agreement). Finally, if an ultrasound is performed at any point during pre- or post-abortion care, a report should be drafted, specifying any potential gynecologic abnormalities found, but its absence must not delay the scheduling of the abortion (best practice agreement).

Prolonged and post-term pregnancies: guidelines for clinical practice from the French College of Gynecologists and Obstetricians (CNGOF)

The duration of pregnancy varies between 40(+0) and 41(+3) weeks. Conventionally, and essentially arbitrarily, a pregnancy is considered to be "prolonged" after 41(+0) weeks, but the infant is not considered "post-term" until 42(+0) weeks (Professional consensus). A term birth thus occurs during the period from 37(+0) to 41(+6) weeks. In France, prolonged pregnancies (≥41(+0)weeks) involve 15-20% of pregnant women, and post-term pregnancies (≥42(+0) weeks) approximately 1%. The frequency of post-term pregnancies is very heterogeneous: in Europe and the United States, it ranges from 0.5% to 10% according to country. In prolonged pregnancies, the cesarean section rate-especially the emergency cesarean rate-is multiplied by approximately 1.5 (grade B). From 37(0-6) to 43(0-6) weeks, the risk of perinatal mortality increases regularly, from 0.7‰ to 5.8‰. Meconium aspiration syndrome is responsible for substantial morbidity and mortality, and its incidence increases regularly between 38(+0) and 42(+6) weeks, from 0.24‰ to 1.42‰ (grade B). Similarly, the risks of neonatal acidosis (grade B), 5-min Apgar scores less than 7 (grade B) and admissions to neonatal intensive care (grade B) increase progressively between 38(+0) and 42(+6) weeks. These risks appear to double for post-term growth-restricted newborns (grade C). Ultrasound dating of the pregnancy makes it possible to reduce the risk that it will be incorrectly considered prolonged and that labor will therefore be induced unnecessarily. To harmonize practices, if the crown-rump length (CRL) is correctly measured (this measurement should be taken between 11(+0) and 13(+6) weeks, when CRL should measure from 45 to 84mm), ultrasound dating based on it should be used to determine the official date pregnancy began, regardless of its difference from the date assumed by the patient or estimated based on the date of the last menstrual period. This rule does not apply to pregnancies by IVF, for which the date pregnancy began is defined by the date of oocyte retrieval (Professional consensus). From 37(0-6) to 43(0-6) weeks, the risk of perinatal mortality increases regularly and there is no threshold at which a clear increase in perinatal mortality becomes visible. Fetal monitoring by cardiotocography (CTG) that begins at 41(+0) weeks would cover approximately 20% of women and reduce perinatal morbidity compared with monitoring that begins at 42(+0) weeks (grade C). The frequency recommended for this monitoring ranges between two and three times a week (Professional consensus). For ultrasonography assessment, measurement of the largest fluid pocket is recommended, because measurement of the amniotic fluid index (that is, the sum of the four quadrants) is accompanied by more diagnoses of oligohydramnios, inductions of labor, and cesareans for fetal distress without any improvement in neonatal prognosis (grade A). The practice of assessing the Manning biophysical score increases the number of diagnoses of oligohydramnios and fetal heart rage (FHR) abnormalities and generates an increase in the rates of inductions and cesareans without improving neonatal prognosis. The use of this biophysical score in monitoring prolonged pregnancies is therefore not recommended (grade B). In the absence of a specific disorder, induction of labor can be proposed in patients between 41(+0) and 42(+6) weeks (grade B). Nonetheless, the choice of prolongation beyond above 42(+0) weeks appears to involve an increase in fetal risk, which must be explained to the patient and balanced against the potential disadvantages of induction (Professional consensus). Stripping the membranes can reduce the duration of pregnancy by increasing the number of patients going into labor spontaneously during the week afterward (grade B). Compared to an expectant approach, it does not increase the cesarean section rate (grade A). It reduces recourse to induction by 41% at 41(+0) weeks and by 72% at 42(+0) weeks (grade B), without increasing the risk of either membrane rupture or maternal or neonatal infection (grade B). Used as a tampon or vaginal gel, prostaglandins E2 (PGE2) are an effective method of inducing labor (grade A). They can be used to induce labor successfully, regardless of cervical ripeness (grade A). If misoprostol is chosen, the lowest dose is to be preferred, starting with a vaginal dose of 25μg every 3-6h (grade A). For misoprostol, more powerful studies remain necessary for better defining the doses, routes of administration, tolerance and indications. Misoprostol at any dose is contraindicated in women with uterine scars (grade B). Placement of an intracervical Foley catheter is an effective mechanical means of inducing labor, with less uterine hyperstimulation than prostaglandins and no increase in the cesarean section rate (grade A). Nonetheless, as the risk of infection might be increased, this technique requires more robust evaluation before entering general practice (grade B). In cases of meconium-stained amniotic fluid, pharyngeal aspiration before delivery of the shoulders is not recommended (grade A). The team managing a post-term newborn with meconium-stained amniotic fluid at birth must know how to perform intubation and, if the intubation is not helpful, endotracheal aspiration (grade C) and ventilation with a mask. Routine endotracheal intubation of a vigorous newborn is not recommended (grade A).