Multiple Pregnancy: Knowledge and Practice Patterns of Obstetricians and Gynecologists

Clinician-reported Chorionicity and Zygosity Assignment using single-nucleotide polymorphism-based cell-free DNA Lessons learned from 55,344 Twin Pregnancies

Objective

Prenatal chorionicity assessment relies on ultrasound, which can be confounded by many factors. Noninvasive assessment of zygosity is possible using single nucleotide polymorphism (SNP)‐based cell‐free DNA testing. Our objective was to determine the relationship between provider‐reported chorionicity and SNP‐cfDNA assignment of twin zygosity.

Methods

All twin pregnancy blood samples received by a reference laboratory between September 27, 2017 and September 8, 2021 were included. Chorionicity assignment was requested on the requisition, recorded as; monochorionic (MC), dichorionic, or “don't know”. SNP‐cfDNA zygosity results, monozygotic (MZ) or dizygotic (DZ), were correlated with chorionicity assignment.

Results

59,471 twin samples (median gestational age = 12.0 weeks at draw) were received and analyzed; 55,344 (93.1%) received zygosity assignment. SNP‐cfDNA reported 16,673 (30.1%) MZ and 38,671 (69.9%) as DZ. Provider‐reported chorionicity was compared to the zygosity assignment for each case. Of 6283 provider‐reported MC twins, 318 (5.1%) were reported as DZ using SNP‐cfDNA.

Conclusion(s)

One in 20 suspected MC twin pregnancies were reported as DZ using SNP‐cfDNA. Approximately 30% of 55,344 twin pregnancies were found to be MZ, including cases where chorionicity was unknown. SNP‐cfDNA zygosity assessment is a useful adjunct assessment for twin pregnancies, particularly those reported as MC or without determined chorionicity.

What's already known about the topic?

The assignment of chorionicity early in pregnancy can improve perinatal outcomes of twin pregnancies. Prenatal assessment of chorionicity relies on ultrasound (US), and the accuracy of US can be confounded by many factors, including gestational age (GA) and operator experience. Noninvasive assessment of zygosity is now possible using single nucleotide polymorphism (SNP)‐based cell‐free DNA (cfDNA).

What does this study add?

This is the first population‐based study describing the correlation between cfDNA assessment of zygosity and chorionicity. In 55,344 twin pregnancies, approximately 30% were found to be monozygotic (MZ), including cases where chorionicity was unknown. We found that one in 20 suspected monochorionic (MC) twin pregnancies were reported as dizygotic (DZ) twins (DZ) by SNP‐cfDNA testing. SNP‐cfDNA zygosity assessment is a useful adjunct assessment for twin pregnancies, particularly those reported as MC or without determined chorionicity.

The Association between Placental Histopathology, Fetal Growth Restriction, and Preeclampsia in Twin Pregnancies

OBJECTIVE

This study aims to estimate the association between abnormal placental histopathology, fetal growth restriction (FGR), and preeclampsia (PEC) in twin pregnancies.

STUDY DESIGN

Retrospective cohort study of women with diamniotic twin pregnancies with live births at ≥24 weeks of gestation and available placental pathology. Findings were compared between women with and without FGR, which was defined as a birthweight <10th percentile, using singleton and twin growth curves, and those with and without PEC. The primary study outcome was a composite of abnormal placental histopathology. Chi-square, Fisher's exact, and Student's t-tests were used for analysis.

RESULTS

Among 859 patients with diamniotic twins, 806 (93.8%) had placental pathology. A total of 422 (52.4%) women had at least one twin with FGR, using a singleton growth curve. FGR affected 136 (16.9%) pregnancies when a twin growth curve was applied. There was no significant difference in composite outcome between groups, using either growth curve (45.5 vs. 44.8%, p = 0.84; adjusted odds ratio (aOR): 1.06, 95% CI: 0.79-1.40 and 52.2 vs. 43.7%, p = 0.07; aOR: 1.44, 95% CI: 0.90-2.10). A total of 122 of 789 (15.5%) patients developed PEC. There was no significant difference in composite outcome between patients with and without PEC (41.8 vs. 45.4%, p = 0.46; aOR: 0.79, 95% CI: 0.53-1.18).

CONCLUSION

In twin pregnancies, FGR and PEC are not associated with abnormal placental histopathology. This suggests that the pathologic placental manifestations of these conditions may differ in twins and include factors other than those commonly described in singletons.

Maternal proximity to Central Appalachia surface mining and birth outcomes

Supplemental Digital Content is available in the text.

Maternal residency in Central Appalachia counties with coal production has been previously associated with increased rates of low birth weight (LBW). To refine the relationship between surface mining and birth outcomes, this study employs finer spatiotemporal estimates of exposure.

Practice patterns of obstetric care in twin gestations: the value of MFM consultation

OBJECTIVES

To evaluate the practice patterns among Lebanese obstetricians regarding obstetric care of twins and to compare selected practice patterns between general obstetricians and maternal fetal medicine physicians.

METHODS

Questionnaires distributed during the annual meeting of the Lebanese Society of Obstetrics and Gynecology.

RESULTS

Questionnaires were returned by 69.2% of the 296 physicians approached. Ten percent had fellowship training in Maternal Fetal Medicine (MFM). Thirty-nine percent perform cervical length measurement at 20-24 weeks of gestation and 34% recommend vaginal progesterone in case of a short cervix. When comparing selected practice patterns between MFM & general obstetricians, MFM specialists were less likely to perform cervical cerclage in the first trimester (5.9% versus 49%, p = .001), more likely to offer prenatal screening for aneuploidy (66.6% vs 46.4%, p = .03), less likely to use vaginal progesterone in the second trimester in the case of a short cervix (42.1% vs 61.8%, p = .04), less likely to perform serial ultrasound exam in the third trimester to assess fetal growth (50% vs 78%, p = .005) and more likely to deliver monoamniotic twins at 32-34 weeks of gestation (55% vs 37%, p = .05).

CONCLUSION

Because of the different background of the Lebanese physicians, MFM specialists are more likely to follow obstetric care guidelines in twin gestation.

Adequacy of Using a Three-Item Questionnaire to Determine Zygosity in Chinese Young Twins

The present study examined the adequacy of a three-item parent questionnaire in determining the zygosity of young Chinese twins and whether there was any association between parent response accuracy and some demographic variables. The sample consisted of 334 pairs of same-sex Chinese twins aged from 3 to 11 years. Three scoring methods, namely the summed score, logistic regression, and decision tree, were employed to evaluate parent response accuracy of twin zygosity based on single nucleotide polymorphism (SNP) information. The results showed that all three methods achieved high level of accuracy ranging from 91 to 93 % which was comparable to the accuracy rates in previous Chinese twin studies. Correlation results also showed that the higher the parents' education level or the family income was, the more likely parents were able to tell correctly that their twins are identical or fraternal. The present findings confirmed the validity of using a three-item parent questionnaire to determine twin zygosity in a Chinese school-aged twin sample.

Prenatal Prediction of the Type of Omphalocele Closure by Different Medical Consultants

INTRODUCTION

To evaluate differences between consultants of different disciplines in the prenatal prediction of the type of postnatal surgical closure of an omphalocele.

MATERIAL AND METHODS

Twenty-one images of prenatally detected omphaloceles prior to 24 weeks of gestation were included. A standardized form provided known prenatal information and an ultrasound image for each case. Nineteen consultants were asked to assess the probability of primary closure of an omphalocele and to state which information was the most important for their assessment.

RESULTS

Primary closure (13/21 images) was predicted correctly in 5/13 images. The number of correct predictions per image ranged from 63 to 89%. The type of closure was predicted correctly in 7/8 images of cases which were not closed primarily, ranging from 58 to 84% correct predictions per image. There was no significant difference between consultants of different disciplines. Individual accuracy ranged from 10 to 62%. The consultants regarded omphalocele content as the most important information (34%) for counseling.

DISCUSSION

The consultants did not differ in their prenatal judgment of the primary closure of an omphalocele. The consultants tended to be too negative in their assessment, since 75% assessed the probability of primary closure overall to be <60%, whereas 62% of the cases were primarily closed. Omphalocele content was the most important information for the consultants' judgment.

Clinical practice in prevention of neonatal HSV infection: a survey of obstetrical care providers in Alberta

OBJECTIVE

To identify the current practice patterns of physicians providing prenatal care in Alberta with respect to prevention of neonatal herpes simplex virus (HSV) infection.

METHOD

A 22-item questionnaire was mailed to all obstetricians and family physicians providing obstetrical care in Alberta. The questionnaire included demographic and practice details, and details of management of patients with a history or symptoms of HSV lesions, including practice in prescribing antiviral therapy, recommending elective Caesarean section, and ordering serology. Two reminders were mailed as necessary.

RESULTS

Responses were received from 89 obstetricians (57%) and 94 family physicians (54%). Antiviral therapy was prescribed for the prevention of neonatal HSV infection in the third trimester by 97% of obstetricians versus 84% of family physicians (P = 0.007), with acyclovir being the most commonly prescribed agent. Caesarean section was offered "most of the time" to women with primary HSV infection in the third trimester by 65% of physicians, to women with prodromal symptoms during the intrapartum period by 57% (no significant differences between groups), and to women with HSV lesions by 92% of obstetricians and 82% of family physicians (P = 0.032). Women with a negative HSV history but whose partner had known HSV were offered serological testing "most of the time" by 30% of physicians (no significant difference between groups).

CONCLUSION

Despite the encouraging survey results, obstetrical providers should be encouraged to offer Caesarean section to women with a primary HSV infection in the third trimester and to offer serological testing in discordant couples. These simple strategies can help to prevent neonatal HSV infection and its long-term consequences.

Suspected twin-twin transfusion syndrome: how often is the diagnosis correct and referral timely?

OBJECTIVES

The purpose of this study was to describe a single center's experience with referrals suspected to have twin-twin transfusion syndrome.

METHODS

A retrospective review was performed for patients with suspected twin-twin transfusion syndrome referred to a fetal treatment center between November 1, 2006, and June 1, 2010. Data were collected regarding diagnosis, treatment, and follow-up.

RESULTS

Of the 324 patients referred for twin-twin transfusion syndrome, the diagnosis was confirmed in 249 (77%): Quintero stage I in 28 (11%), stage II in 50 (20%), stage III in 150 (60%), stage IV in 15 (6%), and stage V in 6 (2%). Ten patients presented too late for any intervention, including 6 cases of stage V disease with either single- or dual-twin death and 4 patients who imminently delivered. Of the 249 confirmed cases, 200 (84%) patients elected to undergo laser photocoagulation. The average gestational age ± SD for referral evaluation for laser-treated cases was 20.9 ± 5.7 weeks (median, 20.5 weeks). The other 75 patients who were referred for suspected twin-twin transfusion syndrome had a diagnosis of either a discordant amniotic fluid volume that did not meet the criteria for Quintero stage I twin-twin transfusion syndrome (56%) or selective intrauterine growth restriction (44%).

CONCLUSIONS

Our data suggest that patients with confirmed twin-twin transfusion syndrome are referred with advanced stages of disease (69% stages III-V), with 59% of referrals made after 20 weeks' gestation. Such a referral pattern calls into question the current frequency of sonographic surveillance used by many obstetricians. Revisions of current practice guidelines emphasizing the importance of more frequent examinations in monochorionic twin gestations beginning at 16 weeks' gestation should be considered.

Screening for Down syndrome: changing practice of obstetricians

OBJECTIVE

We sought to assess the impact of American College of Obstetrician and Gynecologists (ACOG) guidelines on the practices and knowledge of obstetricians regarding screening for Down syndrome 1 year later.

STUDY DESIGN

A questionnaire on Down syndrome screening was mailed to 968 ACOG Fellows and Junior Fellows.

RESULTS

The response rate was 53%. The majority (95%) of respondents offer Down syndrome screening to all pregnant patients; 70% of general obstetricians offer the first-trimester screen and 86% the quad screen. Almost two-thirds (63%) of respondents are offering patients >/= 1 combination of first- and second-trimester screening tests. For women aged < 35 years, 70% offer amniocentesis selectively and 15% routinely. Chorionic villus sampling is offered less frequently. Respondents who more closely read the bulletin were more likely to say their practice had changed, answered more knowledge questions correctly, and felt more qualified to counsel patients. Most (85%) obstetricians personally counsel patients about Down syndrome risk and screening tests. The majority (94-95%) of respondents have access to adequate resources for screening within a 90-minute drive.

CONCLUSION

Obstetricians have adopted a new paradigm for Down syndrome screening. First-trimester screening has been incorporated into prenatal care. Experience with these current screening tests will likely influence future guidelines and challenge the long-standing tradition of offering diagnostic testing based on maternal age. This study highlights the need for concise, unambiguous guidelines and a need to address unresolved issues in Down syndrome screening.

Antenatal sonographic prediction of twin chorionicity

OBJECTIVE

We sought to determine the accuracy of antenatal diagnosis of twin chorionicity at a single tertiary care center and assess the consequences of incorrect diagnoses.

STUDY DESIGN

Twins with chorionicity diagnosed by ultrasound < or = 24 weeks' gestation were retrospectively reviewed. Chorionicity was assigned by sonographic findings including placental location(s), the lambda and T-signs, and/or fetal gender(s). Postnatal diagnosis was determined by placental histopathologic examination. Medical records of antenatal-postnatal discordant chorionicities were reviewed for adverse sequelae.

RESULTS

Chorionicity was correctly assigned antenatally in 392/410 (95.6%) twins. The sensitivity, specificity, and positive and negative predictive values of monochorionicity assessed < or = 14 weeks were 89.8%, 99.5%, 97.8%, and 97.5%. Corresponding statistical values for the second trimester were 88.0%, 94.7%, 88.0%, and 94.7%. Two cases of inaccurate antenatal diagnoses affected patient counseling or were associated with adverse clinical outcomes.

CONCLUSION

Antenatal assessment of chorionicity is accurate; however, incorrect diagnoses do occur and can affect reliable patient counseling and management.

Maternal complications of multifetal pregnancy

This article reviews the common maternal complications encountered in multifetal gestations.

Contemporary clinical issues in outpatient obstetrics and gynecology: findings of the Collaborative Ambulatory Research Network, 2001-2004: part II

Obstetrician/gynecologists are taking on more primary care responsibilities and thus are expected to have a wider base of medical knowledge on a variety of women's health issues. The Collaborative Ambulatory Research Network (CARN) was created in 1990 to investigate issues pertinent to women's health and to the practice of obstetrics and gynecology in the outpatient setting. This article summarizes the findings of CARN studies from 2001 to 2004, covering topics of abnormal pregnancy outcomes, complications of pregnancy, and psychologic disorders. Each study provides a glimpse into the current practice patterns, attitudes, and knowledge of the practicing obstetrician/gynecologist. Although aggregate results suggest that clinicians are consistent and knowledgeable in traditional areas of practice, there appears to be a need for comprehensive educational programs to increase clinicians' comfort level with and knowledge of many primary care issues.