The value of quantitative ultrasound tissue characterization of the cervix and rapid fetal fibronectin in predicting preterm delivery

Accuracy of the combination of commercially available biomarkers and cervical length measurement to predict preterm birth in symptomatic women: A systematic review

An accurate prognostic method for preterm birth (PTB) could avoid unnecessary treatment(s) with potentially negative effects. The objective was to explore the prognostic accuracy of commercially available bedside cervicovaginal biomarker tests in combination with cervical length (CL) compared to CL measurement alone and/or a biomarker test alone, for PTB within 7 days after testing symptomatic women at 22-34 weeks. The MEDLINE, Cochrane, Embase and Web of Science databases were searched from inception to August 28th, 2019. Seven hundred and eight articles were identified and screened using Rayyan. Studies reporting on the predictive accuracy of combined tests compared to CL or biomarker alone for the prediction of PTB within 7 days of testing in symptomatic women with intact membranes were included. A piloted data extraction form was used. Direct comparisons of the prognostic accuracy of the combination test with CL measurement or a biomarker alone were done, as well as comparisons of prognostic accuracy of the included combination tests (indirect comparisons). Twelve articles were included (seven on fetal fibronectin, four on phosphorylated insulin-like growth factor binding protein-1, one comparing both). A variety of CL cut-offs was reported. The results could not demonstrate superiority of a combination method compared to single methods. Due to data scarcity and quality, the superiority of either predictive test for PTB, either combination or single, cannot be demonstrated with this systematic review. We recommend further research to compare available biomarkers.

Shear wave elastography of the uterine cervix under different conditions with inter-operator agreement analysis

Purpose

Shear wave elastography (SWE) is a relatively new technique for measuring tissue elasticity. Its implementation for assessing the tissue of the cervix is evolving, and SWE analyses of healthy, nonpregnant cervixes is the first step in understanding other SWE changes related to cervical pathologies; nevertheless, some challenges in the use of the technique still require investigation. We aimed to target the consistency of healthy cervix shear wave elastography measurements and examine the changes induced by patient-related factors.

Material and methods

Elastograms were obtained at the internal and external os in the anterior (IA, EA) and posterior (IP, EP) portions of the cervix using a transvaginal approach in eight postmenopausal and 25 premenopausal women. Measurements with a standard deviation of over 20% and patients who presented with colour loss or heterogeneity were excluded from the study. Shear wave elastography assessments were performed using a Toshiba Aplio 500 version 6. Statistical significance was defined as a p value less than 0.10, due to the small number of patients.

Results

The mean speeds obtained at the external os on the anterior and posterior aspects was 3.17 ± 0.85 m/s and 3.18 ± 0.84 m/s, respectively, and at the internal os, the results on the anterior and posterior aspects were 3.38 ± 0.73 m/s and 3.53 ± 0.81 m/s, respectively. The difference in speed among all regions was statistically significant (p < 0.05). Fifteen patients were also analysed by a second radiologist with a similar experience level as that of the first. Nine measurements for IP, 13 measurements for IA, 11 measurements for EP, and 15 measurements for EA were performed. The correlation coefficients between the two sets of measurements were 0.46, 0.30, 0.67, and 0.51, respectively. There was no difference in the SWE values with respect to age, parity, and gravidity for any of the regions. The SWE values at the IA, IP, and EA regions between the postmenopausal and premenopausal women were significantly different (p = 0.038, p = 0.059, p = 0.065).

Conclusions

The posterior portion of the internal os is most likely to undergo inaccurate SWE measurement among the different anatomical positions. The correlation between radiologists was found to be different for different locations in the cervix. More studies are needed to determine the SWE values of the healthy cervix and the agreement levels between radiologists.

Quantitative Ultrasound Analysis of Proximal and Distal Cervical Tissue Echogenicity in Premature Cervical Remodeling

OBJECTIVES

To determine whether a novel, noninvasive quantitative ultrasound (US) technique can detect differences in proximal and distal cervical tissue echogenicity in women with and without a shortened cervical length (CL).

METHODS

We conducted a retrospective case-control study of singleton pregnancies at 16 to 26 weeks' gestation in which a transvaginal US examination was performed to measure CL from 2013 to 2015. Initial CLs in cases and controls were less than 2.5 cm and 2.5 cm or greater, respectively. For each US image, a region of interest was selected in the proximal and distal cervical stroma, in both the anterior and posterior cervical lips. The Floyd-Steinberg dithering algorithm transformed grayscale pixels in each region of interest into a binary map. A histogram tabulated the number of black and white pixels, allowing determination of the percent echogenicity. The difference in the percent echogenicity was calculated by subtracting the distal cervical echogenicity (average of anterior and posterior lips) from the proximal cervical echogenicity (average of anterior and posterior lips).

RESULTS

Ultrasound images from 177 women were analyzed. There was a difference in the percent echogenicity (P < .0001) when comparing women with a short cervix (mean ± SD, 9.8 ± 10.1; n = 102) to women with a normal CL (17.2 ± 9.5; n = 75). Differences were attributable to changes in proximal (P < .008) rather than distal cervical echogenicity. Regardless of CL, the proximal cervix was more echogenic than the distal cervix.

CONCLUSIONS

A quantitative US analysis of cervical tissue can detect differences in echogenicity between the proximal and distal cervix in the second trimester. Proximal cervical echogenicity is lower with CL of less than 2.5 cm compared to a normal CL.

The fetal fibronectin test: 25 years after its development, what is the evidence regarding its clinical utility? A systematic review and meta-analysis

Background: The identification of women at risk for preterm birth should allow interventions which could improve neonatal outcome. Fetal fibronectin, a glycoprotein which acts normally as glue between decidua and amniotic membranes could be a good marker of impending labour when its concentration in cervicovaginal secretions between 22 and 36 weeks of gestation is ≥50 ng/mL. Many authors worldwide have tested this marker with many different methodologies and clinical settings, but conclusions about its clinical use are mixed. It is time for a comprehensive update through a systematic review and meta-analysis.Methods: We searched PubMed, Cochrane Library, and Embase, supplemented by manual search of bibliographies of known primary and review articles, international conference papers, and contact with experts from 1-1990 to 2-2018. We have selected all type of studies involving fetal fibronectin test accuracy for preterm delivery. Two authors independently extracted data about study characteristics and quality from identified publications. Contingency tables were constructed. Reference standards were preterm delivery before 37, 36, 35, 34, and 32 weeks, within 28, 21, 14, or 7 d and within 48 h. Data were pooled to produce summary likelihood ratios for positive and negative tests results.Results: One hundred and ninety-three primary studies were identified allowing analysis of 53 subgroups. In all settings, none of the summary likelihood ratios were >10 or <0.1, thus indicating moderate prediction, particularly in asymptomatic women and in multiple gestations.Conclusions: The fetal fibronectin test should not be used as a screening test for asymptomatic women. For high-risk asymptomatic women, and especially for women with multiple pregnancies, the performance of the fetal fibronectin test was also too low to be clinically relevant. Consensual use as a diagnostic tool for women with suspected preterm labor, the best use policy probably still depends on local contingencies, future cost-effectiveness analysis, and comparison with other more recent available biochemical markers.

New model for predicting preterm delivery during the second trimester of pregnancy

In this study, a new model for predicting preterm delivery (PD) was proposed. The primary model was constructed using ten selected variables, as previously defined in seventeen different studies. The ability of the model to predict PD was evaluated using the combined measurement from these variables. Therefore, a prospective investigation was performed by enrolling 130 pregnant patients whose gestational ages varied from 17⁺⁰ to 28⁺⁶ weeks. The patients underwent epidemiological surveys and ultrasonographic measurements of their cervixes, and cervicovaginal fluid and serum were collected during a routine speculum examination performed by the managing gynecologist. The results showed eight significant variables were included in the present analysis, and combination of the positive variables indicated an increased probability of PD in pregnant patients. The accuracy for predicting PD were as follows: one positive – 42.9%; two positives – 75.0%; three positives – 81.8% and four positives – 100.0%. In particular, the combination of ≥2× positives had the best predictive value, with a relatively high sensitivity (82.6%), specificity (88.1%) and accuracy rate (79.2%), and was considered the cut-off point for predicting PD. In conclusion, the new model provides a useful reference for evaluating the risk of PD in clinical cases.

Strain at the internal cervical os assessed with quasi-static elastography is associated with the risk of spontaneous preterm delivery at ≤34 weeks of gestation

AIM

To evaluate the association between cervical strain assessed with quasi-static elastography and spontaneous preterm delivery.

METHODS

Quasi-static elastography was used to estimate cervical strain in 545 pregnant women with singleton pregnancies from 11 weeks to 28 weeks of gestation. Cervical strain was evaluated in one sagittal plane and in the cross-sectional planes of the internal cervical os and external cervical os. The distribution of strain values was categorized into quartiles for each studied region and their association with spontaneous preterm delivery at ≤34 weeks and at <37 weeks of gestation was evaluated using logistic regression.

RESULTS

The prevalence of spontaneous preterm delivery at <37 weeks of gestation was 8.2% (n=45), and that at ≤34 weeks of gestation was 3.8% (n=21). Strain in the internal cervical os was the only elastography value associated with spontaneous preterm delivery. Women with strain values in the 3rd and 4th quartiles had a significantly higher risk of spontaneous preterm delivery at ≤34 weeks and at <37 weeks of gestation when compared to women with strain values in the lowest quartile. When adjusting for a short cervix (<25 mm) and gestational age at examination, women with strain values in the 3rd quartile maintained a significant association with spontaneous preterm delivery at ≤34 weeks (OR 9.0; 95% CI, 1.1-74.0; P=0.02), whereas women with strain values in the highest quartile were marginally more likely than women with lowest quartile strain values to deliver spontaneously at ≤37 weeks of gestation (OR 95% CI: 2.8; [0.9-9.0]; P=0.08).

CONCLUSION

Increased strain in the internal cervical os is associated with higher risk of spontaneous preterm delivery both at ≤34 and <37 weeks of gestation.

Overview of the methods available for biomechanical testing of the uterine cervix in vivo

OBJECTIVE

To give an overview of the methods available for biomechanical testing of the non-pregnant and pregnant uterine cervix in vivo.

METHODS

The following databases were searched. PubMed, Embase, and Cochrane Library. Additional studies were identified from reference lists. Only studies on in vivo biomechanical testing on both pregnant and non-pregnant women were included.

MAIN OUTCOME MEASURES

Estimation of distensibility, compressibility, and biochemical composition of the uterine cervix.

RESULTS

The distensibility methods evaluated a physiologic variable and might serve as a gold standard; however, they may never be clinically useful as they involve instrumentation of the cervical canal. The compression methods evaluated an unphysiological variable but despite that, they seemed to evaluate biologically relevant figures and were non-invasive. Of the methods evaluating the biomechanical properties indirectly, those based on ultrasound may be clinically useful. Other indirect methods only measured variables within the most superficial layer of the distal uterine cervix, so further studies are needed to evaluate whether these measurements reflect the entire organ. Both compression methods and indirect methods were similar or superior to the Bishop score and to cervical length measurements regarding prediction of spontaneous preterm delivery and successful induction of labor in small studies.

CONCLUSION

The methods may have the potential to detect the biomechanical changes in the uterine cervix before the cervical length has shortened. The most promising methods need large-scale clinical testing regarding induction of labor and preterm delivery before they can be used in the clinic.

In vivo assessment of the biomechanical properties of the uterine cervix in pregnancy

Measuring the stiffness of the cervix might be useful in the prediction of preterm delivery or successful induction of labor. For that purpose, a variety of methods for quantitative determination of physical properties of the pregnant cervix have been developed. Herein, we review studies on the clinical application of these new techniques. They are based on the quantification of mechanical, optical, or electrical properties associated with increased hydration and loss of organization in collagen structure. Quasi-static elastography determines relative values of stiffness; hence, it can identify differences in deformability. Quasi-static elastography unfortunately cannot quantify in absolute terms the stiffness of the cervix. Also, the current clinical studies did not demonstrate the ability to predict the time point of delivery. In contrast, measurement of maximum deformability of the cervix (e.g. quantified with the cervical consistency index) provided meaningful results, showing an increase in compliance with gestational age. These findings are consistent with aspiration measurements on the pregnant ectocervix, indicating a progressive decrease of stiffness along gestation. Cervical consistency index and aspiration measurements therefore represent promising techniques for quantitative assessment of the biomechanical properties of the cervix.

Effect of depth on shear-wave elastography estimated in the internal and external cervical os during pregnancy

AIM

To investigate the effect of depth on cervical shear-wave elastography.

METHODS

Shear-wave elastography was applied to estimate the velocity of propagation of the acoustic force impulse (shear wave) in the cervix of 154 pregnant women at 11-36 weeks of gestation. Shear-wave speed (SWS) was evaluated in cross-sectional views of the internal and external cervical os in five regions of interest: anterior, posterior, lateral right, lateral left, and endocervix. Distance from the center of the ultrasound (US) transducer to the center of each region of interest was registered.

RESULTS

In all regions, SWS decreased significantly with gestational age (P=0.006). In the internal os, SWS was similar among the anterior, posterior, and lateral regions and lower in the endocervix. In the external os, the endocervix and anterior regions showed similar SWS values, lower than those from the posterior and lateral regions. In the endocervix, these differences remained significant after adjustment for depth, gestational age, and cervical length. SWS estimations in all regions of the internal os were higher than those of the external os, suggesting denser tissue.

CONCLUSION

Depth from the US probe to different regions in the cervix did not significantly affect the SWS estimations.

Cervical strain determined by ultrasound elastography and its association with spontaneous preterm delivery

OBJECTIVE

To determine if there is an association between cervical strain, evaluated using ultrasound elastography, and spontaneous preterm delivery (sPTD) <37 weeks of gestation.

METHODS

One hundred and eighty nine (189) women at 16-24 weeks of gestation were evaluated. Ultrasound elastography was used to estimate cervical strain in three anatomical planes: one mid-sagittal in the same plane used for cervical length measurement, and two cross sectional images: one at the level of the internal cervical os, and the other at the level of the external cervical os. In each plane, two regions of interest (endocervix and entire cervix) were examined; a total of six regions of interest were evaluated.

RESULTS

The prevalence of sPTD was 11% (21/189). Strain values from each of the six cervical regions correlated weakly with cervical length (from r=-0.24, P<0.001 to r=-0.03, P=0.69). Strain measurements obtained in a cross sectional view of the internal cervical os were significantly associated with sPTD. Women with strain values ≤25th centile in the endocervical canal (0.19) and in the entire cervix (0.14) were 80% less likely to have a sPTD than women with strain values >25th centile [endocervical: odds ratio (OR) 0.2; 95% confidence interval (CI), 0.03-0.96; entire cervix: OR 0.17; 95% CI, 0.03-0.9]. Additional adjustment for gestational age, race, smoking status, parity, maternal age, pre-pregnancy body mass index, and previous preterm delivery did not appreciably alter the magnitude or statistical significance of these associations. Strain values obtained from the external cervical os and from the sagittal view were not associated with sPTD.

CONCLUSION

Low strain values in the internal cervical os were associated with a significantly lower risk of spontaneous preterm delivery <37 weeks of gestation.

Three-dimensional volumetric gray-scale uterine cervix histogram prediction of days to delivery in full term pregnancy

OBJECTIVE

Our aim was to figure out whether volumetric gray-scale histogram difference between anterior and posterior cervix can indicate the extent of cervical consistency.

METHODS

We collected data of 95 patients who were appropriate for vaginal delivery with 36th to 37th weeks of gestational age from September 2010 to October 2011 in the Department of Obstetrics and Gynecology, Korea University Ansan Hospital. Patients were excluded who had one of the followings: Cesarean section, labor induction, premature rupture of membrane. Thirty-four patients were finally enrolled. The patients underwent evaluation of the cervix through Bishop score, cervical length, cervical volume, three-dimensional (3D) cervical volumetric gray-scale histogram. The interval days from the cervix evaluation to the delivery day were counted. We compared to 3D cervical volumetric gray-scale histogram, Bishop score, cervical length, cervical volume with interval days from the evaluation of the cervix to the delivery.

RESULTS

Gray-scale histogram difference between anterior and posterior cervix was significantly correlated to days to delivery. Its correlation coefficient (R) was 0.500 (P = 0.003). The cervical length was significantly related to the days to delivery. The correlation coefficient (R) and P-value between them were 0.421 and 0.013. However, anterior lip histogram, posterior lip histogram, total cervical volume, Bishop score were not associated with days to delivery (P >0.05).

CONCLUSION

By using gray-scale histogram difference between anterior and posterior cervix and cervical length correlated with the days to delivery. These methods can be utilized to better help predict a cervical consistency.

A novel method for evaluating uterine cervical consistency using vaginal ultrasound gray-level histogram

AIMS

To evaluate uterine cervical consistency using a vaginal ultrasound gray-level histogram.

METHODS

Vaginal ultrasound and digital examination were performed for 214 women with low-risk singleton pregnancy during 27-30(th) pregnancy week. The mean gray-level (MGL) of an ultrasound gray-level histogram, representing the echogenicity of a region of interest, was measured in the midsection of anterior and posterior cervical walls. The difference in MGL between anterior and posterior (AP difference) was related to the Bishop sub-score for cervical consistency (0, 1, or 2), determined before ultrasound.

RESULTS

A larger positive AP difference indicated significantly lower Bishop sub-score. After analyzing the receiver operator characteristic curves for the AP difference, a value of 1.42 and -1.98 was the best cut-off value to determine a hard cervix (score 0) and a soft cervix (score 2), respectively. To identify a hard cervix, this test had 71% sensitivity and 82% specificity. For a soft cervix, it was 66% and 87%, respectively.

CONCLUSIONS

A more echogenic anterior than posterior cervix indicates a hard cervix; the greater the difference in echogenicity between anterior and posterior walls the harder the cervix. The difference in MGL of the ultrasound gray-level histogram may enable objective evaluation of cervical consistency.

Quantitative ultrasound assessment of cervical microstructure

The objective of this preliminary study was to determine whether quantitative ultrasound (QUS) can provide insight into, and characterization of, uterine cervical microstructure. Throughout pregnancy, cervical collagen reorganizes (from aligned and anisotropic to disorganized and isotropic) as the cervix changes in preparation for delivery. Premature changes in collagen are associated with premature birth in mammals. Because QUS is able to detect structural anisotropy/isotropy, we hypothesized that it may provide a means of noninvasively assessing cervical microstructure. Thorough study of cervical microstructure has been limited by lack of technology to detect small changes in collagen organization, which has in turn limited our ability to detect abnormal and/or premature changes in collagen that may lead to preterm birth. In order to determine whether QUS may be useful for detection of cervical microstructure, radiofrequency (rf) echo data were acquired from the cervices of human hysterectomy specimens (n = 10). The angle between the acoustic beam and tissue was used to assess anisotropic acoustic propagation by control of transmit/receive angles from -20 degrees to +20 degrees. The power spectrum of the echo signals from within a region of interest was computed in order to investigate the microstructure of the tissue. An identical analysis was performed on a homogeneous phantom with spherical scatterers for system calibration. Power spectra of backscattered rf from the cervix were 6 dB higher for normal (0 degree) than steered (+/- 20 degrees) beams. The spectral power for steered beams decreased monotonically (0.4 dB at +5 degrees to 3.6 dB at +20 degrees). The excess difference (compared to similar analysis for the phantom) in normally-incident (0 degree) versus steered beams is consistent with scattering from an aligned component of the cervical microstructure. Therefore, QUS appears to reliably identify an aligned component of cervical microstructure; because collagen is ubiquitously and abundantly present in the cervix, this is the most likely candidate. Detection of changes in cervical collagen and microstructure may provide information about normal versus abnormal cervical change and thus guide development of earlier, more specific interventions for preterm birth.

Transvaginal cervical length measurement for prediction of preterm birth in women with threatened preterm labor: a meta-analysis

OBJECTIVES

To integrate data on the performance of cervical length measurement for the prediction of preterm birth in symptomatic women.

METHODS

MEDLINE, SCOPUS and manual searches for studies with transvaginal ultrasound measurement of the cervical length in symptomatic women were carried out. Random effects models were used for data integration, and pooled test estimates of sensitivity, specificity, and positive and negative likelihood ratios (LR+ and LR-) were calculated along with their 95% CIs.

RESULTS

Twenty-eight studies fulfilled the selection criteria. For birth within 1 week from presentation, the pooled sensitivity, specificity, LR+ and LR- of cervical length < 15 mm were 59.9% (95% CI, 52.7-66.8%), 90.5% (95% CI, 89.0-91.9%), 5.71 (95% CI, 3.77-8.65) and 0.51 (95% CI, 0.33-0.80), respectively. The same estimates for studies with presentation at or before 34 + 0 weeks were 71.0% (95% CI, 60.6-79.9%), 89.8% (95% CI, 87.4-91.9%), 5.19 (95% CI, 2.29-11.74) and 0.38 (95% CI, 0.11-1.34), respectively. For prediction of birth before 34 weeks, the pooled sensitivity, specificity, LR+ and LR- of cervical length < 15 mm were 46.2% (95% CI, 34.8-57.8%), 93.7% (95% CI, 90.7-96.0%), 4.31 (95% CI, 2.73-6.82) and 0.63 (95% CI, 0.38-1.04), respectively. There was considerable heterogeneity across studies in most estimates.

CONCLUSIONS

Measurement of cervical length in symptomatic women can detect a significant proportion of those who will deliver within 1 week and help to rationalize their management. The considerable heterogeneity across studies may be indicative of methodological flaws, which either were not reported at all or were under-reported.

Frequency domain near-infrared spectroscopy of the uterine cervix during cervical ripening

OBJECTIVE

Preterm labor is a common obstetric complication. Clinical evaluation of cervical ripening to predict preterm labor has a substantial inter- and intraobserver variability. We used frequency domain near-infrared spectroscopy (FD-NIRS) to non-invasively investigate the changes of the optical properties (i.e., absorption and scattering of light) in the uterine cervix during drug-induced cervical ripening.

METHODS

Ten volunteers scheduled for abortion were examined. Optical properties of the uterine cervix were measured and physiological parameters were calculated prior to and after induction of cervical ripening using topical misoprostol. Mean relative changes, +/-standard error of the mean as well as statistical significance using the t-test were calculated for oxy- and deoxyhemoglobin, total hemoglobin, oxygen-saturation, and water. The wavelength-dependent decrease of scattering (scatter power) was calculated by an exponential fit and tested with the Wilcoxon test.

RESULTS

Misoprostol induced a decrease in total hemoglobin of 21 +/- 6% (P < 0.05), a decrease in oxyhemoglobin of 22 +/- 6% (P < 0.05), a decrease in deoxyhemoglobin of 16 +/- 11% and an increase of 36 +/- 8% (P < 0.005) in water content. The scatter power was significantly lower (P < 0.05) after cervical ripening.

CONCLUSION

Our results show that FD-NIRS is a promising diagnostic tool to detect changes in cervical concentrations of hemoglobin and water. A severe tissue edema, probably due to a hormone-induced inflammatory process, seems to be important for cervical ripening. The reduction in total hemoglobin is likely to be a consequence of the increased water content of the tissue resulting in a dramatic increase of the distance between vessels. We propose this technology to assess the cervical ripening and eventually to predict preterm labor.

An Analysis of Antenatal Hospitalization in Canada, 1991–2003

OBJECTIVES

To examine the incidence and temporal trends of hospitalization during pregnancy, and provide additional information on maternal morbidity among Canadian women.

METHODS

A population-based cohort study was conducted using the Canadian Institute for Health Information's Discharge Abstract Database between fiscal year 1991/92 and 2002/03. This database included antenatal hospitalizations for all hospital deliveries (N=3,103,365) in Canada except for those occurring in Manitoba and Quebec. Temporal trends, and variations in the non-delivery antenatal hospitalization ratio (per 100 deliveries) by maternal age and province or territory were quantified. Primary causes for antenatal hospitalization, the lengths of in-hospital stay, and changing pattern by maternal age and time period were compared.

RESULTS

The overall antenatal hospitalization ratio declined by 43%, from 24.0 per 100 deliveries in 1991/92 to 13.6 in 2002/03. Younger women tended to be hospitalized more frequently than older women: 27.1 per 100 deliveries for women aged less than 20 years and 21.5 per 100 deliveries for 20-24 years, respectively, compared to 11.5 per 100 for women aged 35-39 years. The antenatal hospitalization ratio varied greatly by province/territory--from 12.2 per 100 deliveries in Ontario to 30.7 in the Yukon. Threatened preterm labour, antenatal hemorrhage, hypertensive disorders, severe vomiting and diabetes remained the five most common causes for antenatal hospitalization, although the trends for the first four declined dramatically from 1991/92 to 2002/03. Younger women were more likely to be admitted for threatened preterm labour and severe vomiting, while older women were more likely to be admitted for antenatal hemorrhage and hypertensive disorders.

CONCLUSIONS

The decline in antenatal hospitalization may reflect changes in management of pregnancy complications, e.g., transition from in-hospital care to out-of-hospital care, and introduction of antepartum home care programs. Information on interprovincial/territorial variations in antenatal hospitalization may be helpful in directing future maternal health care.