Experiences of cohabiting partners of women diagnosed with cancer during pregnancy: a qualitative study.

PURPOSE: When a pregnant woman is diagnosed with cancer, she faces complex and unique challenges while navigating both obstetric and oncological care. Despite often being the primary support for women diagnosed with cancer during pregnancy (CDP), little is known about the experiences of their partners. We undertook an in-depth exploration of the experiences of partners of women diagnosed with CDP in Australia. METHODS: Semi-structured interviews were conducted with partners of women diagnosed with CDP treated in Australia. Interviews explored partners' inclusion in decision making and communication with health professionals and their own coping experiences. Data were analysed thematically. RESULTS: Data from interviews with 12 male partners (N = 12) of women diagnosed with CDP were analysed. Two unique themes relevant to partners were identified: 'Partners require support to adjust to changing roles and additional burdens' and 'Treating the couple as a team facilitates agency and coping, but partners' needs are placed second by all'. CONCLUSION: Partners of women diagnosed with CDP commonly experience unique stressors and a substantial shift in previously established roles across multiple domains including medical advocacy, household coordination and parenting. Partners' coping is interlinked with how the woman diagnosed with CDP is coping. Inclusion of partners in treatment decisions and communications, and considering partners' wellbeing alongside that of the woman with CDP, is likely to be supportive for partners. In turn, this is likely to enhance the quality of support that women diagnosed with CDP receive from their partners.

An audit of the maternal medicine clinic: Cancer and pregnancy.

AIMS: To explore the incidence and complexity of women presenting for maternity care who require concurrent cancer care, and to report the birth outcomes of these women. MATERIALS AND METHODS: A retrospective audit of women attending a 'high risk' maternal medicine clinic at an Australian tertiary maternity hospital between 1 October 2021 and 30 April 2023 was conducted. The inclusion criteria were a diagnosis of cancer and a concurrent pregnancy, or a diagnosis of cancer prior to the current pregnancy. Clinic lists and coding data were screened via the electronic medical record to identify potential subjects. Data were collected from the individual maternity and neonatal records. RESULTS: Forty of 705 (5.7%) women attending the maternal medicine clinic met the inclusion criteria, of which ten had a new diagnosis of cancer in pregnancy and 30 presented for maternity care after a previous diagnosis of cancer. Cancer therapy during pregnancy included surgery and chemotherapy. Most pregnancies (92.5%) resulted in term deliveries (≥37 weeks gestation). Four neonates were preterm, and one was small-for-gestational-age. Caesarean section delivery and post-partum haemorrhage were more common than expected, but the rate of other adverse pregnancy outcomes was consistent with the background population. Over half of neonates required neonatal intensive care unit / special care nursery admission but the indications for admission were common, self-limiting conditions, and the length of stay was short (mean <5.0 days). CONCLUSIONS: Approximately 6% of women attending the maternal medicine clinic had a current or previous diagnosis of cancer. Most pregnancies resulted in term deliveries and neonatal outcomes were excellent.

Three trajectories of gestational weight gain identified in an Australian twin study.

OBJECTIVES: Gestational weight gain (GWG) has been associated with maternal and child health outcomes, but knowledge of appropriate GWG for twin gestations is limited. STUDY DESIGN: The Peri/Postnatal Epigenetic Twins Study is a prospective twin cohort study of 250 women and their twin children in Melbourne, Australia. We modeled trajectories of GWG using group-based growth modeling and compared these trajectories to GWG categories (within, above, or below current GWG recommendations for twin pregnancy). We fitted robust linear and Poisson regression models to assess associations of maternal pre-pregnancy and gestational exposures with risk of gaining weight outside the recommendations. RESULTS: Of the 250 women enrolled in the PETS, GWG measures were available for 172 women. Forty-seven percent of women had GWG within the current recommendations. We identified three GWG trajectories - 23.6% of women had low GWG throughout pregnancy, 34.5% had average GWG throughout pregnancy, and 42.0% had average initial GWG, followed by high GWG from trimester two until delivery. Gestational diabetes mellitus (GDM) was associated with increased risk of inadequate GWG (RR: 2.40, 95%CI: 1.53, 3.75). Pre-pregnancy obesity (RR: 1.88, 95%CI: 1.09, 3.26) and hypertensive disorders of pregnancy (RR: 2.64, 95%CI: 1.20, 5.81) were associated with increased risk of excessive GWG. CONCLUSIONS: More than half of the women in the PETS did not meet the current GWG recommendations. Women with GDM or hypertensive disorders were more likely to gain weight outside these guidelines. More research is needed to establish comprehensive guidelines for twin pregnancies.

Gestational weight gain is associated with childhood height, weight and BMI in the Peri/Postnatal Epigenetic Twins Study.

Multifetal pregnancies are at risk of adverse maternal, neonatal and long-term health outcomes, and gestational weight gain (GWG) is a potentially modifiable risk factor for several of these. However, studies assessing the associations of GWG with long-term health in twins are rare, and studies which do assess these associations in twins often do not account for gestational age. Since longer gestations are likely to lead to larger GWG and lower risk of adverse outcomes, adjusting for gestational age is necessary to better understand the association of GWG with twin health outcomes. We aimed to explore long-term associations of GWG-for-gestational-age with twin anthropometric measures. The Peri/Postnatal Epigenetic Twins Study (PETS) is a prospective cohort study, which recruited women pregnant with twins from 2007 to 2009. Twins were followed-up at 18 months and 6 years of age. GWG-for-gestational-age z-scores were calculated from pre-pregnancy weight and weight at delivery. We fitted regression models to assess associations of GWG with twin weight, height and BMI at birth, 18 months, and 6 years. Of the 250 women in the PETS, 172 had GWG measured throughout pregnancy. Overall, higher GWG-for-gestational-age z-scores were associated with higher birthweight (ß: 0.32 z-scores, 95% Confidence Interval (95% CI): 0.19, 0.45), BMI (ß: 0.29 z-scores, 95% CI: 0.14, 0.43) and length (ß: 0.27 z-scores, 95% CI: 0.09, 0.45). However, these associations were not observed at 18 months or 6 years of age. GWG was associated with twin length, weight and BMI at birth but not during childhood. Further research is needed to determine the long-term effects of GWG on twin health outcomes.

Experiences of health professionals treating women diagnosed with cancer during pregnancy and proposals for service improvement.

OBJECTIVE: To examine the experiences, needs, and perceptions of health professionals(HPs) treating women diagnosed with cancer during pregnancy(gestational cancer, GC). METHODS: Interviews were undertaken with Australian HPs who had treated women diagnosed with GC over the previous five years. HPs were recruited via social media, and professional and community networks. Questions focussed upon HPs' confidence caring for these women, whether current guidelines/training met their needs, psychological impacts of care provision, and service gaps. Interview data were analysed thematically. RESULTS: Twenty-seven HPs were interviewed; most were oncology HPs(22/27) with experience caring for women with gestational breast cancer and 13 had a breast-specific clinical focus (e.g. breast surgeon). Many were currently treating women with GC(48%) or had in the last 6-12 months(29.6%). Four themes were identified: A clinically complex case, Managing multi-disciplinary care, Centralised resources for health professionals, and Liaison, information and shared experiences for women. HPs found this population personally challenging to treat. They reported initial uncertainty regarding treatment due to infrequent exposure to GC, limited resources/information, and the need to collaborate with services with which they did not usually engage. Solutions offered include centralised resources, clinical liaison/care coordinators, and connecting women with GC with peer support. CONCLUSIONS: HPs perceived women with GC as a vulnerable, complex population and experienced challenges providing comprehensive care; particularly when treatment was delivered at geographically separated hospitals. Systemic changes are needed to optimise comprehensive care for these women. Their insights can guide the development of more integrated cancer and obstetric care, and better HP support.

Cancer during pregnancy: A qualitative study of healthcare experiences of Australian women.

OBJECTIVES: To identify features enhancing the quality of healthcare experiences for women with gestational cancer, and explore the impact of the heterogeneous Australian healthcare system on those experiences. METHODS: Semi-structured, qualitative interviews were conducted with women diagnosed with any cancer during pregnancy in the last five years. Recruitment occurred during 2018-2019 via social media and professional, clinical and community networks. Questions related to women's experiences of their healthcare, wellbeing and psychosocial needs. Interviews were analysed thematically. RESULTS: Study participants (n = 23) received treatment in the private sector (n = 10), public sector (n = 8), or both (n = 5). Five interview themes were found: Control over healthcare; Trust in clinicians, hospitals and systems; Coordination of care; An uncommon diagnosis; Holistic, future-oriented care. Women were most likely to have had a positive healthcare experience when (a)care was well-coordinated and adjusted to meet their unique needs/challenges, and (b)women perceived their care went beyond their immediate medical needs and encompassed future psychosocial wellbeing, including preparation for postpartum challenges. CONCLUSION: Existing 'usual care' in the public and/or private sector for both the pregnancy and the cancer is insufficient to meet these women's needs. Prioritising psychological wellbeing including psychosocial needs, and communication and planning around fertility and postnatal challenges are essential for this population.

The Value of Twins for Health and Medical Research: A Third of a Century of Progress.

In 1984, Hrubec and Robinette published what was arguably the first review of the role of twins in medical research. The authors acknowledged a growing distinction between two categories of twin studies: those aimed at assessing genetic contributions to disease and those aimed at assessing environmental contributions while controlling for genetic variation. They concluded with a brief section on recently founded twin registries that had begun to provide unprecedented access to twins for medical research. Here we offer an overview of the twin research that, in our estimation, best represents the field has progress since 1984. We start by summarizing what we know about twinning. We then focus on the value of twin study designs to differentiate between genetic and environmental influences on health and on emerging applications of twins in multiple areas of medical research. We finish by describing how twin registries and networks are accelerating twin research worldwide.

The Significance of Yolk Sac Number in Monoamniotic Twins.

BACKGROUND: Detection of a single yolk sac on early first trimester ultrasound was previously thought to be a reliable diagnostic feature of monochorionic monoamniotic (MCMA) twin pregnancies. OBJECTIVES: To determine the frequency of two yolk sacs in MCMA twin pregnancies and the association of yolk sac number with pregnancy outcomes. METHODS: A retrospective cohort analysis of MCMA twins managed at a tertiary obstetric centre from January 2003 until February 2017. All MCMA twin pregnancies were diagnosed on tertiary centre ultrasound and, where possible, placental histopathology postnatally. All MCMA twin pregnancies, including conjoined twins, with available first trimester ultrasounds from 5 to 11 weeks' gestation were included in the analysis. MCMA pregnancies without available first trimester ultrasounds and triplet pregnancies which included a MCMA pair were excluded from the study. RESULTS: Sixty-seven MCMA cases were identified over 14 years. Thirty-eight cases were included in the analysis. There was one yolk sac identified in 26 cases (68%) and two yolk sacs in 12 cases (32%). Two yolk sacs were associated with a higher proportion of male fetuses (33%, 4 out of 12, vs. 8%, 2 out of 26; p = 0.01). There were no other significant differences between one and two yolk sacs for maternal or neonatal outcomes. CONCLUSIONS: Two yolk sacs are present in up to a third of all MCMA twin pregnancies, dispelling the original concept that a single yolk sac is diagnostic of MCMA pregnancies. Yolk sac number should not be used to determine amnionicity. The presence of two yolk sacs on first trimester ultrasound is associated with an increased rate of male fetuses. The number of yolk sacs has no other significant impact on perinatal outcomes.

Does Gestational Diabetes Cause Additional Risk in Twin Pregnancy?

It has been suggested that the risk of adverse perinatal outcomes in twin pregnancies is exacerbated by concomitant gestational diabetes mellitus (GDM). This study aimed to assess the risk incurred by twin pregnancy and by a diagnosis of GDM, separately, on the development of poor perinatal outcomes. A retrospective cohort study was conducted on all pregnant women at a tertiary center between 2016 and 2017. The impact of GDM and twin pregnancies on perinatal outcomes - birth weight above the 90th centile for gestational age, cesarean delivery, clinical neonatal hypoglycemia, and premature delivery (before 37 weeks' gestation) - was assessed using univariate and multivariate analyses. Overall, 13,527 women were eligible for the study; 11,915 were uncomplicated singleton pregnancies; 1379 of these had GDM; 194 were twin pregnancies, and 39 of these had GDM. Univariate analyses showed that twin pregnancies were associated with a higher risk of all perinatal outcomes except macrosomia. In the multivariate analyses, twin pregnancy was a much higher predictor of cesarean delivery (OR 8.40, 95% CI [6.25, 11.49], p < .0001) and preterm birth (OR 58.82, 95% CI [31.25, 125], p < .0001) compared to GDM but GDM was a higher predictor of neonatal hypoglycemia (OR 4.87, 95% CI [3.74, 6.29], p < .0001). Twin pregnancy is more strongly associated with all adverse perinatal outcomes except macrosomia. GDM does not increase risk of adverse perinatal outcomes except for neonatal hypoglycemia.

Single Intrauterine Death in Twins: The Importance of Fetal Order.

Perinatal mortality is higher in twins. Effects of twin order have not previously been studied in the context of single fetal demise. Our objective was to determine whether death of the fetus more proximal to the cervix will result in worse perinatal outcomes. Our population included multiple pregnancies with two viable fetuses confirmed prior to 20 weeks' gestation with the subsequent death of at least one twin. All the pregnancies were managed at The Royal Women's Hospital, Melbourne between 2006 and 2014. We excluded pregnancies of higher order multiples, the death of both twins simultaneously, and cases with incomplete outcome data. Maternal and neonatal data were reviewed. Of 46 pregnancies included, in 24 (52%), the dead twin was presenting. Gestational age at delivery was significantly earlier in these cases (mean difference: -5.0 weeks, 95% CI [-7.4, -2.6], p < .001), and emergency cesarean rates were higher 67% versus 32% (OR 4.29, 95% CI [1.25, 14.7], p = .02). There were no differences in the frequency of chorioamnionitis, preterm prelabor rupture of membranes, or placental abruption. Survival rates for co-twins were similar in both groups (presenting 83%; not presenting 91%; OR 0.41, 95% CI [0.07, 2.50], p = .29). The increase in neonatal morbidities was related to prematurity rather than to order. Findings were more common in dichorionic twins. Analysis was limited by a small sample size. If the dead twin is presenting, delivery is likely to occur earlier, with associated morbidity for the survivors. This is especially relevant for dichorionic twin pregnancies.

Pregnancy risk factors associated with birthweight of infants born to Australian Aboriginal women in an urban setting - a retrospective cohort study.

BACKGROUND: A key focus of the Closing the Gap campaign is to reduce low birthweight in Aboriginal babies. Limited research exists on factors affecting Aboriginal birthweight in urban areas. METHODS: Retrospective cohort analysis of 38,382 births (38,167 non-Aboriginal, 215 Aboriginal) at the Royal Women's Hospital in Melbourne from January 2010 to December 2015. Aboriginal status was defined by mothers who identified themselves and their baby as Aboriginal or Torres Strait Islander. The aim was to examine the association of maternal health risk behaviours and obstetric complications with birthweight of infants born to Australian Aboriginal women birthing in an urban setting. RESULTS: Aboriginal babies had a lower mean birthweight than non-Aboriginal babies (mean difference -290 g; 95% confidence interval [CI] -413, - 166 g), but when accounting for gestational age and sex there was little difference (mean difference 5 g; 95% CI -53, 6 g). Aboriginal babies were significantly more likely to be delivered preterm < 37 weeks (23.3% vs 7.9%, odds ratio [OR] 3.58; 95% CI 2.58, 4.95) and be of low birthweight < 2500 g (22.3% vs 6.7%, OR 4.03; 95% CI 2.90, 5.60) or very low birthweight < 1500 g (9.8% vs 1.8%, OR 5.81; 95% CI 3.67, 9.16). Aboriginal mothers were significantly more likely to be teenage mothers (9.8% vs 1.6%, OR 5.72; 95% CI 3.54, 9.24), smoke cigarettes throughout the pregnancy (53.8% vs 5.6%, OR 17.2; 95% CI 12.8, 23.0), and use drugs (26.5% vs 2.4%, OR 14.3; 95% CI 10.4, 19.6) during pregnancy, all of which were associated with lower birthweight. Aboriginal mothers were also more likely to have a mental health diagnosis (49.5% vs 18.8%, OR 3.77; 95% CI 2.86, 4.97), be overweight (59.9% vs 42.6%, OR 1.88; 95% CI 1.39, 2.56) and have diabetes (15.3% vs 7.3%, OR 2.31; 95% CI 1.59, 3.35) which were all associated with higher birthweight. CONCLUSIONS: Aboriginal babies born in metropolitan Melbourne are more likely to be of low birthweight compared with non-Aboriginal babies, which in turn was related to higher rates of prematurity and not to being small for gestational age.

Neonatal outcomes among twins following assisted reproductive technology: an Australian population-based retrospective cohort study.

BACKGROUND: While their incidence is on the rise, twin pregnancies are associated with risks to the mothers and their babies. This study aims to investigate the likelihood of adverse neonatal outcomes of twins following assisted reproductive technology (ART) compared to non-ART twins. METHODS: A retrospective population study using the Australian National Perinatal Data Collections (NPDC) which included 19,662 twins of ≥20 weeks gestational age or ≥ 400 g birthweight in Australia. Maternal outcomes and neonatal outcomes (preterm birth, low birth weight, resuscitation and neonatal death) were compared. Generalized Estimating Equations were used to assess the likelihood of any neonatal outcomes, with adjusted odds ratio (AOR) and 95% confidence intervals (CI) presented. Weinberg's differential rule was used to estimate monozygotic twin rate. RESULTS: ART mothers were 3.3 years older than non-ART mothers. The rates of pregnancy-induced hypertension and gestational diabetes were significantly higher for ART mothers than non-ART mothers (12.2% vs. 8.4%, p <  0.01) and (9.7% vs. 7.5%, p <  0.01) respectively. The incidence of monozygotic twins was 2.0% for ART twins and 1.1% for non-ART twins. Compared with non-ART twins, ART twins had higher rates of preterm birth (AOR 1.13, 95% CI: 1.05-1.22), low birth weight (AOR 1.13, 95% CI: 1.05-1.22), and resuscitation (AOR 1.26, 95% CI: 1.17-1.36). Liveborn ART twins had 28% (AOR 1.28, 95% CI 1.09-1.50) increased odds of having any adverse neonatal outcome compared to liveborn non-ART twins, especially for opposite-sex ART twins (AOR 1.42, 95% CI 1.11-1.82). CONCLUSION: As ART twins had higher rates of adverse outcome, special prenatal care is recommended. Couples accessing ART should be fully informed of the risk of adverse outcome of twin pregnancies.

Outcome of Twin Pregnancies Complicated by a Neural Tube Defect.

Twin pregnancies discordant for neural tube defects (NTD) is a management dilemma. Risks of preterm delivery from polyhydramnios must be balanced with the risks of selective termination (ST) of the anomalous fetus. We investigated the prevalence of twin pregnancies discordant for NTD and the rate of pregnancy complications in our institution over a 10-year period. Cases were obtained by searching the hospital ultrasound database and findings were confirmed by expert review of ultrasound images. Outcomes of ST and expectant management were assessed. Each unaffected co-twin was assigned to three consecutive twin pregnancy controls matched by chorionicity and maternal age. Primary outcome was birth before 34 weeks' gestation. Secondary outcomes were small for gestational age, mode of delivery, neonatal unit admission, and neonatal death. In total, 13 pregnancies were identified as potential cases. Of these, 11 were included in the analysis: 9 dichorionic diamniotic and 2 monochorionic diamniotic twins. Seven cases had ST and four were managed expectantly. We found 100% (4/4) of expectantly managed pregnancies delivered <34 weeks compared with 14% (1/7) of the ST group (p = .015). Polyhydramnios complicated three expectantly managed pregnancies and one pregnancy in the ST group. The birthweight SD score of all unaffected co-twins was ≥-2. The case-control analysis showed a higher rate of polyhydramnios in twin pregnancies discordant for NTD compared with controls, but little evidence for differences between groups in delivery rates <34 weeks, birthweight, neonatal unit admission, or neonatal death. ST warrants serious consideration to avoid potential complications to the unaffected co-twin.

Expression of Homeobox Gene HLX and its Downstream Target Genes are Altered in Placentae From Discordant Twin Pregnancies.

A discordant twin gestation, in which one fetus is significantly growth restricted, compared to the other normal twin, is a unique model that can be used to elucidate the mechanism(s) by which the intrauterine environment affects fetal growth. In many model systems, placental transcription factor genes regulate fetal growth. Transcription factors regulate growth through their activation or repression of downstream target genes that mediate important cell functions. The objective of this study was to determine the expression of the placental HLX homeobox gene transcription factor and its downstream target genes in dizygotic twins with growth discordance. In this cross-sectional study, HLX and its downstream target genes' retinoblastoma 1 (RB1) and cyclin kinase D (CDKN1C) expression levels were determined in placentae obtained from dichorionic diamniotic twin pregnancies (n = 23) where one of the twins was growth restricted. Fetal growth restriction (FGR) was defined as small for gestational age with abnormal umbilical artery Doppler indices when compared with the normal control co-twin. Homeobox gene HLX expression was significantly decreased at both the mRNA and protein levels in FGR twin placentae compared with the normal control co-twin placentae (p < .05). Downstream target genes CDKN1C and RB1 were also significantly decreased and increased, respectively, at both the mRNA and protein levels in FGR twin placentae compared with normal control co-twin placentae (p < .05). Together, these observations suggest an important association between HLX transcription factor expression and abnormal human placental development in discordant twin pregnancies.

The Outcome of Monochorionic Diamniotic Twins Discordant at 11 to 13+6 Weeks' Gestation.

BACKGROUND: Monochorionic diamniotic (MCDA) twin pregnancies are associated with adverse perinatal outcome. Intertwin discordances at the time of nuchal translucency (NT) screening may have a value in the prediction of fetal loss or twin-to-twin transfusion syndrome. We aimed to determine the ability of intertwin NT and crown rump length (CRL) discordances among MCDA twins to predict adverse outcomes. MATERIAL AND METHODS: All MCDA twins with a documented routine ultrasound at 11 to 13+6 weeks' gestation, and known pregnancy outcome between August 2003 and August 2012 were included. Receiver operating characteristic curves were used to determine the ideal NT and CRL discordances cut-off points that maximized the ability to predict adverse outcome, which was defined as any of: death of one or both twins, twin-to-twin transfusion syndrome, or estimated fetal weight or birth weight discordances ≥25%. RESULTS: Of the 89 cases, 20 (22.5%) had at least one adverse outcome. NT discordance was more discriminatory of adverse outcome than was CRL discordance. The optimal values for predicting any adverse outcomes for NT were >23.7% and for CRL >3.5%. The positive predictive values for NT (52.4%) and CRL (29.8%) screening were relatively low; however, the lack of either NT or CRL discordances was more reassuring, with negative predictive values of 86.8% and 86.4%, respectively. CONCLUSIONS: NT discordance is more predictive for adverse fetal outcome in MCDA twins than CRL discordance. Neither NT nor CRL discordance are likely to modify the intensive monitoring required for these very high-risk pregnancies.

Editorial-Special Issue.

Monochorionic twin pregnancies are subject to unique complications that can threaten the life and well-being of both fetuses, resulting in a disproportionate increase in perinatal morbidity and mortality.

The History of Treatment of Twin-to-Twin Transfusion Syndrome.

Historical suggestions of twin-to-twin transfusion syndrome (TTTS) date back to the early 17th century. Placental anastomoses were first reported in 1687; however, it was Schatz who first identified their importance in 1875. He recognized 'the area of transfusion' within the 'villous district' of the placenta, which he named the 'third circulation'. This article describes how the management of TTTS has evolved as we have gained a more sophisticated understanding and appreciation of the complex vascular anastomoses that exist in monochorionic twin placentae. Currently, fetosopic laser occlusion is the preferred treatment option for TTTS.

The urologist's role in multidisciplinary management of placenta percreta.

OBJECTIVE: To evaluate urological interventions in patients with placental adhesive disorders in our collaborative experience at a tertiary referral centre. PATIENTS AND METHODS: We performed a retrospective analysis of a prospectively collected data set, consisting of all women that presented with placental adhesive disorders at the Royal Women's Hospital from August 2009 to September 2013. Patients who required urological intervention were identified and perioperative details were retrieved. RESULTS: Of the 49 women that presented with placental adhesive disorders, 36 (73.5%) underwent urological interventions. The patients were divided into three groups: planned hysterectomy (37 patients), planned conservative management (five) and undiagnosed placenta percreta (seven). In the planned hysterectomy group, 29 patients underwent preoperative cystoscopy and ureteric catheter placement. In 10 patients (34%), the placenta partially invaded the bladder and/or ureter, requiring urological repair. In the conservative management group, four underwent preoperative cystoscopy and ureteric catheter placement, and one case required closure of a cystotomy. Of the seven patients with undiagnosed percreta, two were noted to have bladder involvement requiring repair at the time of Caesarean hysterectomy. CONCLUSION: Patients with placental adhesive disorders frequently require urological intervention to prevent or repair injury to the urinary tract. These cases are best managed in specialist centres with multidisciplinary expertise including urologists and interventional radiologists.

A review of the mechanisms and evidence for typical and atypical twinning.

The mechanisms responsible for twinning and disorders of twin gestations have been the subject of considerable interest by physicians and scientists, and cases of atypical twinning have called for a reexamination of the fundamental theories invoked to explain twin gestations. This article presents a review of the literature focusing on twinning and atypical twinning with an emphasis on the phenomena of chimeric twins, phenotypically discordant monozygotic twins, mirror-image twins, polar body twins, complete hydatidiform mole with a coexistent twin, vanishing twins, fetus papyraceus, fetus in fetu, superfetation, and superfecundation. The traditional models attributing monozygotic twinning to a fission event, and more recent models describing monozygotic twinning as a fusion event, are critically reviewed. Ethical restrictions on scientific experimentation with human embryos and the rarity of cases of atypical twinning have limited opportunities to elucidate the exact mechanisms by which these phenomena occur. Refinements in the modeling of early embryonic development in twin pregnancies may have significant clinical implications. The article includes a series of figures to illustrate the phenomena described.