Determination of amniotic fluid volume in twin pregnancies: ultrasonographic evaluation versus operator estimation

MRI Findings in Third-Trimester Opioid-Exposed Fetuses, With Focus on Brain Measurements: A Prospective Multicenter Case-Control Study

BACKGROUND. The opioid epidemic has profoundly affected infants born in the United States, as in utero opioid exposure increases the risk of cognitive and behavioral problems in childhood. Scarce literature has evaluated prenatal brain development in fetuses with opioid exposure in utero (hereafter opioid-exposed fetuses). OBJECTIVE. The purpose of this study is to compare opioid-exposed fetuses and fetuses without opioid exposure (hereafter unexposed fetuses) in terms of 2D biometric measurements of the brain and additional pregnancy-related assessments on fetal MRI. METHODS. This prospective case-control study included patients in the third trimester of pregnancy who underwent investigational fetal MRI at one of three U.S. academic medical centers from July 1, 2020, through December 31, 2021. Fetuses were classified as opioid exposed or unexposed in utero. Fourteen 2D biometric measurements of the fetal brain were manually assessed and used to derive four indexes. Measurements and indexes were compared between the two groups by use of multivariable linear regression models, which were adjusted for gestational age (GA), fetal sex, and nicotine exposure. Additional pregnancy-related findings on MRI were evaluated. RESULTS. The study included 65 women (mean age, 29.0 ± 5.5 [SD] years). A total of 28 fetuses (mean GA at the time of MRI, 32.2 ± 2.5 weeks) were opioid-exposed, and 37 fetuses (mean GA at the time of MRI, 31.9 ± 2.7 weeks) were unexposed. In the adjusted models, seven measurements were smaller (p < .05) in opioid-exposed fetuses than in unexposed fetuses: cerebral frontooccipital diameter (93.8 ± 7.4 vs 95.0 ± 8.6 mm), bone biparietal diameter (79.0 ± 6.0 vs 80.3 ± 7.1 mm), brain biparietal diameter (72.9 ± 7.7 vs 74.1 ± 8.6 mm), corpus callosum length (37.7 ± 4.0 vs 39.4 ± 3.7 mm), vermis height (18.2 ± 2.7 vs 18.8 ± 2.6 mm), anteroposterior pons measurement (11.6 ± 1.4 vs 12.1 ± 1.4 mm), and transverse cerebellar diameter (40.4 ± 5.1 vs 41.4 ± 6.0 mm). In addition, in the adjusted model, the frontoocccipital index was larger (p = .02) in opioid-exposed fetuses (0.04 ± 0.02) than in unexposed fetuses (0.04 ± 0.02). Remaining measures and indexes were not significantly different between the two groups (p > .05). Fetal motion, cervical length, and deepest vertical pocket of amniotic fluid were not significantly different (p > .05) between groups. Opioid-exposed fetuses, compared with unexposed fetuses, showed higher frequencies of both breech position (21% vs 3%, p = .03) and increased amniotic fluid volume (29% vs 8%, p = .04). CONCLUSION. Fetuses with opioid exposure in utero had a smaller brain size and altered fetal physiology. CLINICAL IMPACT. The findings provide insight into the impact of prenatal opioid exposure on fetal brain development.

Twin-to-Twin Transfusion Syndrome: Definition, Staging, and Ultrasound Assessment

Objective: The purpose of this article is to review the definition of twin-to-twin transfusion syndrome (TTTS) and the sonographic diagnostic assessment of these cases prior to therapy.

Materials and Methods: The article addresses the terminology used to refer to the condition and describes the systematic ultrasound assessment of the condition, including the ultrasound diagnosis, the staging of the disease, cervical assessment and pre-operative mapping.

Results: From an etymologic and medical point of view, the term ‘fetofetal transfusion’ is more appropriate than ‘TTTS’. However, as the latter, and its attendant acronym TTTS, have been widely adopted in the English language, it is impractical to change at this point. TTTS is defined sonographically in the combined presence of a maximum vertical pocket (MVP) of 8 cm or greater in one sac and 2 cm or less in the other sac, regardless of the gestational age at diagnosis. Staging of the condition using the Quintero staging system is practical, reproducible, and accepted. Transvaginal cervical length assessment should be an integral part of the ultrasound evaluation. Pre-operative mapping to anticipate the location of the placental vascular anastomoses and avoid injuring the dividing membrane is also discussed.

Conclusions: The term ‘TTTS’ can continue to be used in the English medical literature. The condition can be diagnosed and assessed following a systematic ultrasound methodology. The use of such ultrasound methodology breaks the examination into a distinct set of components, assuring a comprehensive examination and proper communication among caregivers.

A systematic review of amniotic fluid assessments in twin pregnancies

The objectives of this systematic review were to examine the reproducibility of sonographic estimates of amniotic fluid volume (AFV) in twin pregnancies, compare the association of sonographic estimates of AFV with dye-determined AFV, and correlate AFV with antepartum, intrapartum, and perinatal outcomes in twin pregnancies. Studies were included if they were adequately powered and investigated antepartum, intrapartum, and/or perinatal adverse outcome parameters in twin gestations. Studies with comparable populations and exclusion criteria were merged into forest plots. Data comparing the accuracy of AFV assessment, correlation of AFV with gestational age, and adverse outcomes were tabulated. Five of the 6 studies investigating AFV by the amniotic fluid index as a function of gestational age reported data fitting a quadratic equation, with fluid volumes peaking at mid gestation and then declining. This trend was less pronounced when AFV was assessed by the single deepest pocket (2 of 4 studies reporting a quadratic fit). Polyhydramnios was associated with prematurity in 2 of 4 studies (1 amniotic fluid index and 1 single deepest pocket), and oligohydramnios was associated with prematurity in 1 single deepest pocket study. Stillbirth was the only intrapartum outcome reported in more than 1 study. Perinatal outcomes associated with polyhydramnios included neonatal death (P < .05 in 1 of 2 studies), low Apgar scores (1 of 2 studies), neonatal intensive care unit admission (1 of 2 studies), and low birth weight (2 of 3 studies).

Polyhydramnios: Causes, Diagnosis and Therapy

Polyhydramnios is defined as a pathological increase of amniotic fluid volume in pregnancy and is associated with increased perinatal morbidity and mortality. Common causes of polyhydramnios include gestational diabetes, fetal anomalies with disturbed fetal swallowing of amniotic fluid, fetal infections and other, rarer causes. The diagnosis is obtained by ultrasound. The prognosis of polyhydramnios depends on its cause and severity. Typical symptoms of polyhydramnios include maternal dyspnea, preterm labor, premature rupture of membranes (PPROM), abnormal fetal presentation, cord prolapse and postpartum hemorrhage. Due to its common etiology with gestational diabetes, polyhydramnios is often associated with fetal macrosomia. To prevent the above complications, there are two methods of prenatal treatment: amnioreduction and pharmacological treatment with non-steroidal anti-inflammatory drugs (NSAIDs). However, prenatal administration of NSAIDs to reduce amniotic fluid volumes has not been approved in Germany. In addition to conventional management, experimental therapies which would alter fetal diuresis are being considered.

Amniotic fluid as a vital sign for fetal wellbeing

Introduction: Amniotic fluid, once thought to merely provide protection and room for necessary movement and growth for the fetus, is now understood to be a highly complex and dynamic system that is studied as a data point to interpret fetal wellbeing. Methods: Assessment of amniotic fluid volume is now routine when performing a sonographic evaluation of fetal status and is an important consideration in the assessment and management of perinatal morbidity and mortality.1,2 In this review, we will cover the dynamics that affect amniotic fluid volume, review methods for measurement and quantification of volume, review definitions for normative data as related to neonatal outcomes, and provide evidence based guidance on the workup and management options for oligoydramnios and polyhydramnios in singleton and twin pregnancies. Conclusions: When abnormalities of fluid exist, appropriate workup to uncover the underlying etiology should be initiated as adverse fetal outcomes are sometimes associated with these variations from normalcy.

Accuracy of Sonographic Amniotic Fluid Volume Assessments in Diamniotic Dichorionic Twin Pregnancies: A Literature Review

This literature review is meant to bring to light the controversy over the most accurate method to assess the amniotic fluid volumes (AFV) in diamniotic-dichorionic (di-di) twin gestations. It is hoped that this may initiate consideration of a standardized method so that all sonographers and interpreting physicians will consistently use the same method. There is no definitive standard method for sonographers to obtain an accurate amount of amniotic fluid. Commonly, sonographers and interpreting physicians agree that the most practical and accurate methods for sonographers to use are the amniotic fluid index, largest vertical pocket, and the two-diameter pocket methods. Although these measurements are fast, noninvasive, and relatively consistent in evaluating the relative amount of AFV, only the dye-determined technique is 100% accurate, especially when the AFV is outside the subjective normal ranges and either oligohydramnios or polyhydramnios is present.

Antepartum management of multifetal pregnancies

Correct antepartum management of multifetal gestations is a critical skill for practitioners of obstetrics. This article reviews important issues surrounding these complicated pregnancies while discussing current management options and recommendations. Topics include antepartum surveillance, preterm labor prediction, diagnosis, and management, and special situations unique to multiple gestations, such as twin-twin transfusion syndrome and death of one twin in utero. It is the authors' hope that this article is comprehensive in enhancing the reader's knowledge of these complex pregnancies.

Growth Aberration in Multiple Pregnancy

Growth of twins and higher-order multiples is an exceptional metabolic challenge for the expecting mother. She is doing much more than a mother of a singleton in terms of nurturing, however. Metabolic requirements need adequate dietary intervention in the form of increased weight gain during early pregnancy. It is normal for multiples to be smaller than singletons. Being smaller than singletons does not necessarily mean that multiples are pathologically growth restricted. It is important to remember that twins and triplets have different growth patterns, and their growth should not be considered by using singleton standards. When a small-for-gestational-age fetus is suspected in a multiple pregnancy, it is advisable to follow or to treat the pregnancy as if it was an SGA singleton.