Correlation between the duration of maternal rest in the left lateral decubitus position and the amniotic fluid volume increase

Fetuses with deceleration of growth improve their growth following maternal rest

OBJECTIVE

The purpose of this study was to determine if fetuses with deceleration of growth velocity resulting in an EFW <10th percentile increase their growth above the 10th percentile following 2 weeks of maternal rest in the left lateral recumbent position.

METHODS

This was a retrospective observational study of 265 fetuses with the prenatal diagnosis of an EFW <10th percentile. Fetuses were classified by four definitions of abnormal growth velocity: (1) a growth velocity less than 20 g/day, (2) 30 percentile decrease in the EFW, (3) 50 percentile decrease in the EFW, and (4) abnormal growth trajectory. Once the fetuses were identified with an EFW <10th percentile the patient was requested to begin 2 weeks of rest in the left lateral recumbent position during her waking hours following which the EFW was reassessed 2 week later to determine the effect of maternal rest on the EFW.

RESULTS

Irrespective of the four types of decreased growth velocity described in the methods section, there was as significant increase (p < 0.001) in the EFW following 2 weeks of maternal rest as follows: (1) growth less than 20 g/day (75%); (2) decrease of 30 or more EFW percentiles (79%); (3) decrease of 50 or more EFW percentiles (64%); and abnormal growth trajectory (77%).

CONCLUSIONS

This suggests an important role of increased maternal cardiac output as the result of resting in the left lateral recumbent position that may be associated with improved fetal growth. These observations should be the basis for future prospective randomized trials to test this hypothesis.

Maternal rest improves growth in small-for-gestational-age fetuses (<10th percentile)

BACKGROUND

Optimal management of fetuses diagnosed as small for gestational age based on an estimated fetal weight of <10th percentile represents a major clinical problem. The standard approach is to increase fetal surveillance with serial biometry and antepartum testing to assess fetal well-being and timing of delivery. Observational studies have indicated that maternal rest in the left lateral position improves maternal cardiac output and uterine blood flow. However, maternal bed rest has not been recommended based on the results of a randomized clinical trial that showed that maternal rest does not improve fetal growth in small-for-gestational-age fetuses. This study was conducted to revisit this question.

OBJECTIVE

This study aimed to determine whether maternal bed rest was associated with an increase in the fetal biometric parameters that reflect growth after the diagnosis of a small-for-gestational-age fetus.

STUDY DESIGN

A retrospective study was conducted on fetuses who were diagnosed as small for gestational age because of an estimated fetal weight of <10th percentile for gestational age. The mothers were asked to rest in the left lateral recumbent position. Fetal biometry was performed 2 weeks after the diagnosis. All fetuses before entry into the study had a previous ultrasound that demonstrated an estimated fetal weight of >10th percentile. To assess the response to bed rest, the change in fetal biometric parameters (estimated fetal weight, head circumference, abdominal circumference, and femur length) after the recommendation of bed rest was computed for 2 periods: (1) before the diagnosis of a weight of <10th percentile vs at the time of diagnosis of a weight of <10th percentile and (2) at the time of diagnosis of a weight of <10th percentile vs 2 weeks after maternal bed rest. For repeated measures, proportions were compared using the McNemar test, and percentile values were compared using the Bonferroni Multiple Comparison Test. A P value of <.05 was considered significant. To describe changes in the estimated fetal weight without bed rest, 2 control groups in which the mothers were not placed on bed rest after the diagnosis of a small-for-gestational-age fetus were included.

RESULTS

A total of 265 fetuses were observed before and after maternal bed rest. The following were observed in this study: (1) after 2 weeks of maternal rest, 199 of 265 fetuses (75%) had a fetal weight of >10th percentile; (2) the median fetal weight percentile increased from 6.8 (interquartile range, 4.4-8.4) to 18.0 (interquartile range, 9.5-29.5) after 2 weeks of bed rest; (3) similar trends were noted for the head circumference, abdominal circumference, and femur length. In the groups of patients who were not asked to be on bed rest, a reassignment to a weight of >10th percentile at a follow-up examination only occurred in 7 of 37 patients (19%) in the Texas-Michigan group and 13 of 111 patients (12%) in the Colorado group compared with the bed rest group (199/265 [75%]) (P<.001).

CONCLUSION

Patients who were prescribed 2 weeks of bed rest after the diagnosis of a fetal weight of <10th percentile had an increase in weight of >10th percentile in 199 of 265 fetuses (75%). This increase in fetal weight was significantly higher than that in the 2 control groups in which bed rest was not prescribed. This observation suggests that bed rest improves fetal growth in a subset of patients.

Impact of maternal posture on fetal physiology in human pregnancy: a narrative review

In numerous medical conditions, including pregnancy, gravity and posture interact to impact physiology and pathophysiology. Recent investigations, for example, pertaining to maternal sleeping posture during the third trimester and possible impact on fetal growth and stillbirth risk highlight the importance and potential clinical implications of the subject. In this review, we provide an extensive discussion of the impact of maternal posture on fetal physiology from conception to the postpartum period in human pregnancy. We conducted a systematic literature search of the MEDLINE database and identified 242 studies from 1991 through 2021, inclusive, that met our inclusion criteria. Herein, we provide a synthesis of the resulting literature. In the first section of the review, we group the results by the impact of maternal posture at rest on the cervix, uterus, placenta, umbilical cord, amniotic fluid, and fetus. In the second section of the review, we address the impact on fetal-related outcomes of maternal posture during various maternal activities (e.g., sleep, work, exercise), medical procedures (e.g., fertility, imaging, surgery), and labor and birth. We present the published literature, highlight gaps and discrepancies, and suggest future research opportunities and clinical practice changes. In sum, we anticipate that this review will shed light on the impact of maternal posture on fetal physiology in a manner that lends utility to researchers and clinicians who are working to improve maternal, fetal, and child health.

Amniotic Fluid: Technical Update on Physiology and Measurement

OBJECTIVE

OUTCOMES: EVIDENCE: A MEDLINE and KFINDER search was used to identify relevant articles, with review of bibliography identified article including Cochrane reviews and recent review articles.

VALUES

The evidence collected was reviewed by the Diagnostic Imaging Committee of the Society of Obstetricians and Gynecologists of Canada. The recommendations were made according to the guidelines developed by The Canadian Task Force on Preventative Health Care (Table 1).

BENEFITS, HARMS AND COSTS

Amniotic fluid assessment by ultrasound has become an integral part of fetal assessment in modern obstetrics. Abnormalities of fluid volume result in obstetrical intervention and further investigations. In Canada, there are no standard definitions of fluid volume estimation, nor a standard approach to assessing fluid. Multiple randomized trials have suggested that using a Single Pocket Estimation technique (rather than the multi pocket assessment approach known as the amniotic fluid index), will result in fewer obstetrical interventions without any increase in adverse outcomes. Recent literature suggests that there are detectable, modest changes in amniotic fluid that can occur within an hour or two of normal physiological maneuvers. This may account for the variability and inconsistent results from repeated assessments within a short period of time which can lead to confusion and generate further testing. This article hopes to describe the limitations of amniotic fluid assessment, promote a standard method of amniotic fluid assessment, and propose a common set of definitions to be used to describe amniotic fluid volume.

SUMMARY STATEMENTS

RECOMMENDATION.

Mise à jour technique sur la physiologie et l'évaluation du liquide amniotique

OBJECTIF

RéSULTATS: SOURCES DES DONNéES PROBANTES: Nous avons effectué une recherche sur MEDLINE et Kfinder pour trouver des articles pertinents, puis avons examiné les bibliographies des articles retenus, notamment des revues Cochrane et des articles de revue récents.

VALEURS

Les données recueillies ont été analysées par le Comité d'imagerie diagnostique de la Société des obstétriciens et gynécologues du Canada. Les recommandations ont été classées selon les critères établis par le Groupe d'étude canadien sur les soins de santé préventifs (Tableau 1). AVANTAGES, DéSAVANTAGES ET COûTS: En obstétrique moderne, l'évaluation du volume de liquide amniotique par échographie fait partie intégrante de l'évaluation fœtale. Toute anomalie donne lieu à une intervention obstétricale et à des examens approfondis. Au Canada, il n'existe aucune définition normalisée associée à l'estimation du volume de liquide amniotique ni aucune approche d'évaluation uniforme. Plusieurs essais randomisés semblent indiquer que l'évaluation de poche unique, plutôt que de plusieurs poches (indice de liquide amniotique), diminue les interventions obstétricales sans augmenter l'incidence de résultats indésirables. La littérature récente laisse croire que des changements légers, mais détectables du liquide amniotique peuvent survenir une heure ou deux suivant des manœuvres physiologiques normales, ce qui pourrait expliquer la variabilité et le manque de cohérence des résultats d'évaluations répétées en peu de temps et ainsi créer de la confusion et donner lieu à d'autres examens. Le présent article vise à décrire les limites de l'évaluation du volume de liquide amniotique, à promouvoir une méthode d'évaluation normalisée et à proposer un ensemble commun de définitions. DéCLARATIONS SOMMAIRES: RECOMMANDATION.

Comparison of the Effect of Maternal Rest in Alternative Lateral Decubitus Positions on the Amniotic Fluid Index: A Randomized Controlled Trial

OBJECTIVES

To analyze the effect of maternal rest in the left and right lateral decubitus positions and resting alone on the amniotic fluid index (AFI).

METHOD

Sixty-nine women with singleton pregnancies and an AFI of 6 to 24 cm at 36 to 40 weeks' gestation were included in this randomized controlled trial. The women were randomized into 2 intervention groups. After initial AFI measurements, group 1 (n = 35) rested in the left lateral position for 15 minutes and then rested in the right lateral position for another 15 minutes. Group 2 (n = 34) rested in the right lateral position for 15 minutes and then rested in the left lateral position for another 15 minutes. To compare differences between groups, AFIs were measured at the end of each 15-minute period while the participants were kept on their backs in a semirecumbent position.

RESULTS

The demographic data, gestational ages, and initial AFI values did not differ between groups (P > .05). In group 1, the initial mean AFI ± SD of 12.25 ± 3.81 increased significantly during the first 15 minutes to 15.17 ± 4.27 and decreased significantly during the second 15 minutes to 13.30 ± 4.29 (P< .001); however, the 30-minute AFI was still significantly higher than the initial value (P = .008). In group 2, the initial AFI change during the first 15 minutes, from 12.83 ± 3.99 to 12.72 ± 3.87, was not significant (P> .05); however, it increased significantly to 15.63 ± 4.14 during the second 15 minutes (P< .001). The 30-minute AFI was still significantly higher than the initial value (P< .001).

CONCLUSIONS

Maternal rest in the right lateral decubitus position does not seem to either increase or decrease the AFI, and resting alone does not increase the AFI in the short term.

Effect of maternal hydration on the amniotic fluid volume during maternal rest in the left lateral decubitus position: a randomized prospective study

OBJECTIVES

The purpose of this study was to evaluate the effect of maternal hydration on amniotic fluid volume during maternal rest in the left lateral decubitus position.

METHODS

Pregnant women (n = 79) with an amniotic fluid index between 6 and 24 cm and a singleton uncomplicated pregnancy at 35 to 40 weeks' gestation were randomized into hydration and control groups. Starting 30 minutes before the measurements, the hydration group drank 250 mL of water at 15-minute intervals (1000 mL/h). After the initial amniotic fluid index measurements, the women in both groups were instructed to rest in the left lateral decubitus position, and the measurements were repeated at 15, 30, 45, 60, 75, and 90 minutes.

RESULTS

The amniotic fluid index increased at each interval in both groups. Although each amniotic fluid index value was higher than the preceding one, only the 15- and 30-minute values in the left lateral decubitus position alone and the 15-, 30-, and 45-minute values in the left lateral decubitus position with maternal hydration were significantly higher than the preceding measurements (P < .05). A similar increase in the amniotic fluid volume was present 15 minutes after assuming the left lateral decubitus position in both groups. However, after 30 minutes, the women in the left lateral decubitus position without maternal hydration needed another 60 minutes for a significant amniotic fluid index increase, whereas the women with maternal hydration needed only another 45 minutes for a significant increase.

CONCLUSIONS

Maternal rest in the left lateral decubitus position with hydration and maternal rest in the left lateral decubitus position alone caused similar increases in the estimated amniotic fluid volume at 15 minutes. However, after 30 minutes, the amniotic fluid volume increased more rapidly in the group with hydration.