Validation of Ultrasound Dating Protocols Using Data From Twins Conceived Through In Vitro Fertilization in Nova Scotia: A Retrospective Cohort Study.

OBJECTIVES: Clinical practice guidelines recommend determining gestational age (GA) for twin pregnancies using the fetal crown rump length (CRL) of the larger fetus. This study investigated whether the CRL of the larger or smaller fetus at 11-14 weeks best predicted in vitro fertilization (IVF) assigned GA. METHODS: A retrospective cohort study of twin pregnancies conceived by IVF ± intracytoplasmic sperm injection, 2004-2022, generated GA estimations for each co-twin CRL at the 11-14 week ultrasound, to determine which fetus (smaller or larger) more consistently predicted IVF-assigned GA. Monoamniotic twins and twins with known structural or vascular abnormalities were excluded. Paired t tests evaluated the ability of CRL to predict GA, and logistic regression evaluated the predictive ability of each of the co-twin groups with increasing size differences. Statistical significance was set at P < 0.05. RESULTS: Viewpoint 6 identified 359 eligible twin pairs. CRL was closest with the smaller fetus (0.38 days); CRL for both the smaller (95% CI 0.16-0.61) and the larger (2.25 days, 95% CI 2.04-2.46) fetus showed deviation from IVF-assigned GA. As the absolute difference between the small and large fetus increased, the ultrasound-estimated GA of the smaller fetus was still consistently closer to IVF-assigned GA. CONCLUSIONS: In this selected population of twins with known GA, the CRL of the smaller fetus more accurately predicted IVF-assigned GA even with increasing differences in fetal size. These findings provide important information for appropriately dating pregnancies to facilitate adherence to national guidelines to monitor for pregnancy complications, and plan frequency and type of fetal surveillance, as well as timing of delivery.

No 375 - Directive clinique sur l'utilisation de l'échographie au premier trimestre.

OBJECTIF: Révision des indications cliniques de l'échographie du premier trimestre. RéSULTATS: L'échographie au premier trimestre offre des avantages cliniques démontrés. DONNéES PROBANTES: Les données probantes ont été révisées au moyen de recherche dans Medline et selon la bibliographie des articles pertinents. VALEURS: Le contenu et les recommandations ont été évalués par les auteurs principaux et le Comité d'imagerie diagnostique de la Société des obstétriciens et gynécologues du Canada. Le niveau d'évidence a été défini en fonction des critères du Groupe d'étude canadien sur les soins de santé préventifs. RECOMMANDATIONS.

No. 375-Clinical Practice Guideline on the Use of First Trimester Ultrasound.

OBJECTIVE: This guideline reviews the clinical indications for first trimester ultrasound. OUTCOME: Proven clinical benefit has been reported from first trimester ultrasound. EVIDENCE: A Medline search and bibliography reviews in relevant literature provided the evidence. VALUES: Content and recommendations were reviewed by the principal authors and the Diagnostic Imaging Committee of the Society of Obstetricians and Gynaecologists of Canada. Levels of evidence were judged as outlined by the Canadian Task Force on Preventive Health Care.

No. 359-Obstetric Ultrasound Biological Effects and Safety.

OBJECTIVE: To review the biological effects and safety of obstetric ultrasound. OUTCOME: Outline the circumstances in which safety may be a concern with obstetric ultrasound. EVIDENCE: The 2005 version of this guideline was used as a basis and updated following a Medline search and review of relevant publications. Sources included guidelines and reports by Health Canada and the American Institute of Ultrasound in Medicine. VALUES: Review by principal author and the Diagnostic Imaging Committee of the SOGC. The quality of evidence and classification of recommendations have been adapted from the Report of the Canadian Task Force on the Periodic Health Examination. BENEFITS, HARMS, AND COSTS: Obstetric ultrasound should only be done for medical reasons, and exposure should be kept as low as reasonably achievable because of the potential for tissue heating. Higher energy is of particular concern in the following scenarios: Doppler studies (pulsed, colour, and power), first trimester ultrasound with a long trans-vesical path (>5 cm), second or third trimester exams when bone is in the focal zone, when scanning tissue with minimal perfusion (embryonic), or in patients who are febrile. Operators can minimize risk by limiting dwell time and exposure to critical structures. It is also important to be aware of equipment-generated exposure information.

Peripartum factors predicting the need for increased doses of postpartum rhesus immune globulin.

OBJECTIVE: To evaluate the need for increased doses of postpartum rhesus immune globulin in a woman at risk for rhesus alloimmunization. METHODS: Using data from the Nova Scotia Atlee Perinatal Database (NSAPD) and the Rh Program of Nova Scotia Database, Rh negative women delivering infants with a birth weight greater than 500 grams and gestational age greater than 20 weeks at the IWK Health Centre from 1998 to 2007 were identified. Within this population, Rh(D) negative women who received both antepartum and postpartum anti-D prophylaxis were identified. Logistic regression was used to estimate peripartum predictive factors for elevated postpartum Kleihauer and the need for administration of additional rhesus immune globulin. RESULTS: The NSAPD and Rh Program Database identified 4323 Rh negative women who received both antepartum and postpartum prophylaxis from 1998 and 2007. Following logistic regression, a postpartum Kleihauer value of > 0.2% was found to be predicted by multiparity (OR 1.47; 95% CI 1.03 to 2.08), multiple gestation (OR 3.03; 95% CI 1.61 to 5.70), antepartum risks for fetomaternal hemorrhage (OR 63.6; 95% CI 30.2 to 134), and Caesarean section (OR 2.03; 95% CI 1.42 to 2.91). A postpartum Kleihauer value of > 0.5% was found to be predicted by antepartum risks for fetomaternal hemorrhage (OR 29.1; 95% CI 12.9 to 65.5), and Caesarean section (OR 2.01; 95% CI 1.18 to 3.42). CONCLUSION: While there are recognized events that increase the risk for Rh(D) alloimmunization, multiparity, multiple gestation, and Caesarean section should be additional factors for consideration, especially with rising rates of CS. Adequate postpartum prophylaxis may be optimized by conducting routine screening for fetomaternal hemorrhage, especially when lower doses of Rh(D) immune globulin are administered.

Spina bifida before and after folic acid fortification in Canada.

BACKGROUND: In 1998, fortification of a large variety of cereal products with folic acid became mandatory in Canada. A multicentric study was carried out to assess the impact of this policy on the frequency of NTDs. The present analysis focused on spina bifida. METHODS: The study population included approximately 2 million livebirths, stillbirths, and terminations of pregnancies because of fetal anomalies among women residing in seven Canadian provinces, from 1993 to 2002. Spina bifida cases were divided according to the upper limit of the defect: upper (cranial, cervical, or thoracic) and lower (lumbar or sacral) defects. Based on published results of red blood cell folate tests, the study period was divided into prefortification, partial fortification, and full fortification periods. RESULTS: A total of 1,286 spina bifida cases were identified: 51% livebirths, 3% stillbirths, and 46% terminations. Prevalence decreased from 0.86/1,000 in the prefortification to 0.40 in the full fortification period, while the proportion of upper defects decreased from 32% to 13%. Following fortification, regional variations in the prevalence and distribution of sites almost disappeared. CONCLUSIONS: Results confirmed the etiologic heterogeneity of spina bifida and the more pronounced effect of folic acid in decreasing the risk of the more severe clinical presentations.

Impact of folic acid food fortification on the birth prevalence of lipomyelomeningocele in Canada.

BACKGROUND: Recent studies reported no reduction in the frequency of lipomeningomyelocele (LMMC) in Hawaii and Nova Scotia after the implementation of a folic acid food fortification policy in 1998, while a marked reduction in the prevalence of other NTDs was observed. This study was performed to assess the prevalence of LMMC in Canada in relation to the timing of food fortification. METHODS: The study population included livebirths, stillbirths, and terminations of pregnancies because of fetal anomaly to women residing in seven Canadian provinces, from 1993 to 2002. In each province, the ascertainment of NTD cases relied on multiple sources, and in addition all medical charts were reviewed. The study period was divided into pre-, partial, and full fortification periods, based on results of red cell folate tests published in the literature. RESULTS: A total of 86 LMMC cases were recorded among approximately 1.9 million live births. The average birth prevalence rate was 0.05/1,000, ranging from a minimum of 0.01/1,000 in 2002 to a maximum of 0.08/1,000 in 1999. There was statistical heterogeneity between years (p = .01), but no pattern compatible with a decrease following fortification. Comparing the full fortification period with the prefortification period, there was a slight but not statistically significant decrease in LMMC birth prevalence. CONCLUSIONS: LMMC seems to be pathogenically distinct from myelomeningocele and more studies are needed to understand the embryologic mechanisms leading to this condition, and the environmental and genetic factors involved in its etiology.

Reduction in neural-tube defects after folic acid fortification in Canada.

BACKGROUND: In 1998, folic acid fortification of a large variety of cereal products became mandatory in Canada, a country where the prevalence of neural-tube defects was historically higher in the eastern provinces than in the western provinces. We assessed changes in the prevalence of neural-tube defects in Canada before and after food fortification with folic acid was implemented. METHODS: The study population included live births, stillbirths, and terminations of pregnancies because of fetal anomalies among women residing in seven Canadian provinces from 1993 to 2002. On the basis of published results of testing of red-cell folate levels, the study period was divided into prefortification, partial-fortification, and full-fortification periods. We evaluated the relationship between baseline rates of neural-tube defects in each province and the magnitude of the decrease after fortification was implemented. RESULTS: A total of 2446 subjects with neural-tube defects were recorded among 1.9 million births. The prevalence of neural-tube defects decreased from 1.58 per 1000 births before fortification to 0.86 per 1000 births during the full-fortification period, a 46% reduction (95% confidence interval, 40 to 51). The magnitude of the decrease was proportional to the prefortification baseline rate in each province, and geographical differences almost disappeared after fortification began. The observed reduction in rate was greater for spina bifida (a decrease of 53%) than for anencephaly and encephalocele (decreases of 38% and 31%, respectively). CONCLUSIONS: Food fortification with folic acid was associated with a significant reduction in the rate of neural-tube defects in Canada. The decrease was greatest in areas in which the baseline rate was high.

SOGC clinical practice guidelines. Ultrasound evaluation of first trimester pregnancy complications. Number 161, June 2005.

OBJECTIVES: First, to review normal embryonic development and the sonographic evidence of early pregnancy failure; second, to review sonographic evidence of ectopic pregnancy. OUTCOMES: First, prediction of pregnancy failure, second, sonographic identification of ectopic pregnancy. EVIDENCE: A MEDLINE search and review of bibliographies in identified articles was conducted. VALUES: The evidence was reviewed by the Diagnostic Imaging Committee along with the principal authors. A quality of evidence assessment was undertaken as outlined in the report of the Canadian Task Force on the Periodic Health Examination (Table 1). BENEFITS, HARMS, AND COSTS: Women presenting with first trimester bleeding may be incorrectly diagnosed with a missed abortion and (or) may be inappropriately reassured about viability. Transvaginal ultrasound provides improved resolution allowing description of early embryonic development characteristics. Improvement in the identification of the sonographic landmark of normal embryonic development and awareness of the sonographic risk factors of pregnancy failure may lead to more successful management strategies. Diagnosis of suspected ectopic pregnancy often involves an assessment of both hormonal markers and sonographic features. Maternal morbidity and mortality can be reduced with an early diagnosis of ectopic pregnancy. RECOMMENDATIONS: There is good (class A) evidence that current ultrasound technology can distinguish between normal and abnormal pregnancies in the first trimester. There is good (class A) evidence that transvaginal ultrasound in conjunction with quantitative-HCG can diagnose ectopic pregnancy.

Prenatal infantile cortical hyperostosis (Caffey's disease): a 'hepatic myeloid hyperplasia-pulmonary hypoplasia sequence' can explain the lethality of early onset cases.

BACKGROUND: Infantile cortical hyperostosis (ICH) is benign and self-limiting when it presents near or after birth but is usually lethal when it presents earlier. METHODS: We present the clinical, ultrasonic, radiographic and pathologic findings in an instructive case of early onset prenatal ICH. RESULTS: A 40-year-old G2P1 woman delivered spontaneously at 22 weeks' gestation. Prenatal ultrasounds showed rib and mandibular abnormalities as well as short humeri. Post-mortem radiographs showed asymmetric hyperostosis in long bones, mandible, scapulae and pelvis with sparing of spine, hands, feet and skull. The affected skeleton showed marked bony sclerosis and ballooning of the diaphyses of the long bones with periosteal sclerosis. A complete autopsy showed characteristic histologic findings in affected bones. Previous reports at 20+ weeks have described anasarca, fetal hydrops, hepatomegaly, and pulmonary hypoplasia. In our case, there was no hydrops/anasarca; hepatomegaly, due to massive extramedullary hematopoiesis with marked myeloid hyperplasia, combined with ribcage abnormalities, caused mild pulmonary hypoplasia. CONCLUSION: We hypothesize that early onset fetal ICH is usually lethal because massive hepatic myeloid hyperplasia sequentially causes: (1) hepatomegaly and, in conjunction with rib abnormalities, mild pulmonary hypoplasia, (2) sinusoidal and pre-sinusoidal portal hypertension followed by ascites/hydrops, and (3) ascites/hydrops-induced severe pulmonary hypoplasia.