ACOG updates recommendations for diagnostic imaging during pregnancy and lactation

http://www.infantrisk.com/content/radiological-procedures-pregnancy

ACOG has issued recommendations addressing the concerns surrounding the use of X-ray, sonography, nuclear medicine, CT and MRI in pregnancy and lactation. The committee opinion was published in October issue of Journal Obstetrics and Gynecology.

These investigative modalities have become an integral part of our diagnostic armamentarium for evaluating acute and chronic conditions. However, there is confusion and fear surrounding these tests among physician and patients alike that many times they are delayed or totally avoided. Many a times breast feeding is stopped while patient undergo these investigations.

The ACOG’s committee on obstetric practice make the following recommendations:

Ultrasonography and MRI are safe and are the imaging modalities of choice in pregnancy and lactation, although they should be availed only when they are expected to answer a relevant clinical dilemma or are provide health benefit to the patient.

Routine radiography, computed tomography (CT) scan, or nuclear medicine imaging techniques exposes the pregnant women to a dose that is much lower than what is associated with fetal harm and so these techniques should be used if deemed necessary in addition to USG or MRI or alone if they answer the relevant clinical question.

The use of gadolinium contrast with MRI is not advised in routine practice and should only be used as contrast if it significantly improve the diagnosis and maternal and fetal outcome during pregnancy.

Breastfeeding need not be interrupted after gadolinium administration.

Nuclear Medicine imaging should be limited to the use of technetium 99m at 5 mGy when indicated during pregnancy. 

Radioactive iodine (iodine 131) readily crosses placenta and is absolutely contraindicated in pregnancy.

Full Text 

For more news, join me on Facebook and Twitter

Virtual reality 3D technology allows parents to meet their unborn child: News from Radiological Society of North America 2016 Annual Conference.

3D virtual model MRI view of fetus at 26 weeks.Photo credit: Image courtesy of Radiological Society of North America

1. New technology combines MRI and Ultrasound data into a 3-D virtual reality model of a fetus.
2. The models are very similar to what the baby will look like after birth and can create any internal fetal organ replica to perfection.
3. Wearing a virtual reality headset, the parents can hear the baby’s heartbeat and see the anatomy. 

Parents may now be able to see their unborn babies developing in realistic 3-D immersive visualizations. This is made possible because of efforts of team of Brazilian researchers said Heron Werner Jr, MD, PhD, from the Clínica de Diagnóstico por Imagem in Rio de Janeiro.

The study was presented at the Radiological Society of North America 2016 Annual Meeting in Chicago on November 30,2016.[i]

“The 3-D fetal models combined with virtual reality immersive technologies may improve our understanding of fetal anatomical characteristics and can be used for educational purposes and as a method for parents to visualize their unborn baby,” said study co-author Heron Werner Jr., M.D., Ph.D., from the Clínica de Diagnóstico por Imagem, in Rio de Janeiro, Brazil.

The new technology transforms MRI and ultrasound data into a 3-D virtual reality model of a fetus. The construction of 3D accurate virtual model starts with the MRI scanning slices that are than sequentially stitched together to form a 3-D image. The physician decides the organ or body part he wants to visualize and   that part is reconstructed including the uterus, placenta, umbilical cord and fetus.  

At the beginning of the study the researchers scanned 6 mm "slices" and put them together, now they scan 1mm slices improving the resolution and producing more clear pictures.

The Virtual reality 3-D model is very similar to what a baby would look like after delivery. The doctors can create a very detailed structure of every organ of the fetal body.

 Werner and colleagues turned to the latest-generation Oculus Rift 2 (Oculus) headset to be used as the virtual reality viewing device. The parents don the device to interact with the baby in this very real immersive sensory environment. Adding the heartbeat by the use of headphone brings them further close to  the baby. Users can simply move their heads to study 3D fetal anatomy close-up.

Oculus device headset 

"The experience with the Oculus Rift has been wonderful," Werner said. "It provides fetal images that are sharper and clearer than ultrasound and MR images viewed on a traditional display." 

The virtual reality model has an array of potential applications, including detection of important structural malformations like cardiac and respiratory. It can also be of great help in cases requiring intrauterine surgeries. Using the models the team can simulate the surgeries in virtual reality.

https://3dprint.com

"We think this is especially interesting for training novice endoscopic surgeons." Dr Werner said.

"We believe that these images will help facilitate a multidisciplinary discussion about some pathologies, in addition to bringing a new experience for parents when following the development of their unborn child." said Dr. Werner.

Currently Dr Werner is working on many projects including creating models to study trisomy 11 and trisomy 18 syndromes, ZIKA syndrome.

The researchers have already used the technique in many cases in Rio that required postnatal surgeries. They are hoping for a broader use of the technology in near future.

Not everyone is ready to jump on the virtual reality 3-D visualizations. Some doctors still prefer the 3D-printed models with a hands-on experience.

---

[i] https://press.rsna.org/timssnet/media/pressreleases/PDF/pressreleasePDF.cfm?ID=1912

Abnormally invasive placenta---Can we predict and do better?

Clinical Pearls:

• Previous cesarean section or uterine surgery is the single most important predisposing factors for Abnormally Invasive placenta.
• One cesarean section increases the risk of AIP seven fold in subsequent pregnancy.
• History of post-partum hemorrhage is also a risk factor for AIP and increases the risk 6 fold in current pregnancy.
• In 70% of cases, the diagnosis of AIP was missed during antenatal period.
• Increasing clinician awareness for incidence of AIP in the high risk patients leads to increased diagnosis in antenatal period.
• Avoiding unnecessary cesarean section is the only way to decrease the incidence of AIP.  

Lowering the Cesarean section rate in the population is the only most effective way in reducing the incidence of Abnormally invasive placenta(AIP) is the conclusion of a large, population based cohort study from the Nordic countries.

The Nordic Obstetric Surveillance Study (NOSS) required obstetricians’ collaboration in reporting AIP, uterine rupture, excessive blood loss and peripartum hysterectomy from 2009-2012. Due to paucity of cases at a single hospital the data was pooled and validated by National Health Registries. 

The data was analyzed and identified 205 cases of AIP amounting to an incidence of 3.4 per 10,000 deliveries.

The study was published in the current issue of British Journal of Obstetrics and Gynecology(BJOG).[1]

The study goal was to gauge the prevalence, risk prediction, predisposing factors, antenatal suspicion, maternal morbidity and birth complications in cases of AIP.

The study confirmed the association between AIP and previous cesarean section or any other previous uterine surgeries like endometrial ablation, and in vitro fertilization. The risk of AIP in subsequent pregnancy is seven fold with one prior Cesarean section to 56-fold after three or more CS.

Placenta previa was the single most important risk factor identified in nearly half of the pregnancies.

 In addition, patient who had postpartum hemorrhage in previous pregnancy have 6 times the risk of AIP in current pregnancy as compared to patients who did not have PPH.

An antenatal diagnosis of AIP can strikingly reduce the complication rate but in nearly two-third of patients (70%) of patients the diagnosis was missed. Of these, 39% had prior CS and 33% had placenta praevia.

Increased awareness about the risk factors among clinicians can raise the index of suspicion and led to more and more patients being diagnosed in prenatal period. Clinicians performing Ultrasound(USG) should have high index of suspicion in high risk women with previous uterine surgery or a placenta over uterine scar. These women should be offered additional sonography.

Nordic countries have lower rates of AIP than US, perhaps due to lower rate of cesarean section and high order cesarean births or better obstetrics facilities. 

But, the only sure way to decrease the incidence of AIP is to avoid unnecessary cesarean delivery, especially the first cesarean section.

---

[1] Thurn L, Lindqvist PG, Jakobsson M, Colmorn LB, Klungsoyr K, Bjarnadóttir RI, Tapper AM, Børdahl PE, Gottvall K, Petersen KB, Krebs L, Gissler M, Langhoff-Roos J, Källen K. Abnormally invasive placenta—prevalence, risk factors and antenatal suspicion: results from a large population-based pregnancy cohort study in the Nordic countries. BJOG 2015; DOI: 10.1111/1471-0528.13547.

Predicting spontaneous preterm birth in twin pregnancies utilizing cervical length and gestational age: Individual patient data meta-analysis.

Multiple births are steadily climbing all around the world. Developed countries making a significantly higher contribution to this rising rate because of women delaying childbirth, elderly mothers and increased use of ARTs.

US twinning rate rose by 101% from 1980 – 2006. About 68,339 twins were born in 1980 that doubled to 137,085 in 2006. The US current twin birth rate is 33.9 per 1,000 live births.

 According to WHO the rate of singleton preterm birth ranges between 5% to 18% for singleton pregnancy worldwide, the average being 11%, while almost 60% of twins are delivered preterm. About 13% of twins are born before 34 weeks and 7% before 32 weeks.

A multitude of prophylactic therapies have been in use like to gain valuable gestational weeks by supplementing progesterone, vaginal pessaries and strict bed rest without substantially significant results.

The next step was to develop essential biomarkers that can predict the chances of preterm births. Cervical length(CL) has long   been used as a predictive indicator of preterm birth. An earlier review has shown that a CL < or=20 mm at 20-24 weeks' gestation was the most accurate in predicting preterm birth at <32 and <34 weeks respectively. Many other studies have combined fetal fibronectin with CL. 

Studies in singleton pregnancies have also shown that the relationship between CL and spontaneous preterm birth (sPTB) is dependent on the Gestational age (GA) at which the USG is done, a shorter CL early in pregnancy has greater significance than the same measurement at a later GA.

Such studies in twins are few with small sample size and are not comparable. Previous meta-analysis has shown a relationship between CL and sPTB in twins, but did not correlate the GA at screening with prediction of sPTB.

This recent study published in the May, 2016 issue of BJOG is a meta-analysis of independent patient data(IPD), and provides a new estimate in which CL and GA are treated as continuous variables to predict weeks at delivery.

Specific data collected for each patient from the original authors of the study included the exact GA at CL screening, the CL measurement in millimeters and the exact GA at birth in weeks and days.

23 studies met the inclusion criteria, resulting in a total of 6188 transvaginal scans, performed on 4409 twin pregnancies. 

In the first analysis, univariate regression was performed to see what other confounders like maternal age, ethnicity, smoking, BMI, chorionicity, parity and study location affects the GA at birth. 

As second analysis multinomial logistic regression model was derived predicting the probabilities of very early preterm, early preterm, late preterm, and term birth using GA at USG and CL as continuous variables.

Important study results were:

• BMI was the only other variable that correlated significantly with GA at birth in the univariate analysis, but when it was incorporated into multinomial logistic regression model with CL and GA at ultrasound, prediction of GA at birth did not improve.
• A short CL measured at ≤20⁺⁰ weeks by USG indicates a probability of birth significantly earlier than if the same CL was taken at a later GA.
• When screening before 18⁺⁰ weeks, any cervical length <30 mm has a higher risk of sPTB at ≤28⁺⁰ weeks in twins than in singletons.Whereas the best prediction of birth between 28⁺¹ and 36⁺⁰ weeks was provided by screening at ≥24⁺⁰ weeks.
• A 100% probability of preterm birth not occurring before 28 weeks is achieved by CL of 65 mm and 43 mm at ultrasound GA at ≤18⁺⁰ weeks and at 22⁺¹ to 24⁺⁰ weeks, respectively.

In the third analysis, the accuracy of the model to correctly predict term delivery as compared to preterm was assessed. The model has a 68.2% true negative rate, classifying correctly those who were predicted to deliver at ≥36⁺¹ weeks, compared with 26.2, 13.3 and 36.2% correctly predicted to deliver at ≤28⁺⁰, 28⁺¹ to 32⁺⁰ and 32⁺¹ to 36⁺⁰ weeks, respectively (true positive rate).

Although effective intervention for sPTB in twins are limited, the study provides risks of very early, early and late preterm birth, so a personalized cost effective delivery plan, optimal timing of corticosteroids and referring to neonatal unit can be managed. It also justifies serial CL measurements, so that early and late sPTB could be predicted.

To conclude the authors, recommend to start the screening at ≤18⁺⁰ weeks with repeat screening at >22⁺⁰ weeks; this best identifies the patients that may deliver very early at ≤28⁺⁰ weeks as well as the more common later group of sPTB between 28⁺⁰ to 36⁺⁰ weeks. 

References:

http://www.cdc.gov/nchs/fastats/multiple.htm

http://www.who.int/mediacentre/factsheets/fs363/en/

http://www.ncbi.nlm.nih.gov/pubmed/24360590

http://onlinelibrary.wiley.com/doi/10.1111/1471-0528.13575/full

http://onlinelibrary.wiley.com/doi/10.1111/1471-0528.13710/full