G Blayney

and 3 more

Objective: To evaluate the impact of twin dating by ultrasound-measured crown-rump length (CRL) of the larger (CRL-L), smaller (CRL-S) or mean twin measurement (CRL-M) on the rates of preterm birth (PTB) and detection of fetal growth restriction. Design: A cohort study. Setting: A tertiary fetal medicine centre (London, UK). Population or sample: All twin pregnancies between 1998 and 2023 who underwent ultrasound assessment of first trimester CRL and fetal growth. Methods: Data collection included CRL measurement, estimated fetal weight (EFW), pregnancy outcome and birthweight (BW) for each twin. Pregnancies were retrospectively re-dated by CRL-S, CRL-L and CRL-M. Main outcome measures: Small for gestational age (SGA) <10 th centile and PTB rates. Results: Of the 1129 twin pairs median CRL was 61mm (IQR:56.0-66.0) and 63mm (IQR:58.4-68.9) for the smaller and larger twin respectively with a mean discordance of 4.0%. Prenatal SGA diagnosis occurred in 19.8% and 23.1% of smaller twins when dated by CRL-S and CRL-L respectively. When pregnancies were dated by CRL-M versus CRL-S or CRL-L there was no difference in prenatal SGA diagnosis (p=0.275 and p=0.419); SGA at birth (p=0.132 and p=0.325); or PTB (p=1.00 and p=0.765 respectively). Conclusions: Dating by the smaller, larger or mean-twin CRL doesn’t significantly alter rates of extreme preterm birth, SGA detection or SGA birth. Dating by the mean twin CRL reduces stigmatisation of the smaller twin, alleviating parental anxiety, whilst retaining the utility of accurate gestational age assessment without impacting on clinical outcomes.
BJOG mini-commentary on BJOG-22-0097This manuscript by McCall et al reports that UK and France have very different approaches to managing women with PAS. More women in France received a uterus conserving approach. Major haemorrhage was more common in the UK series. The authors speculate that this may be related to treatment modality. The ACOG/SMFM committee opinion (Obstet Gynecol 2018;132:e259–75) recommends caesarean hysterectomy as the most generally accepted approach. Does this report imply that we should stop offering hysterectomies and recommend conservative treatment?Before we make up our mind, it is important to consider what else was different in the two cohorts. The case definitions used by UK OSS and PACCRETA investigators were different. However, the authors of the current report have included only those cases that satisfied a harmonised definition. UK prevalence (1.7/10 000) was significantly lower as compared to that from France (4.2/10 000). This raises the question: Is UK under-reporting or is France over-reporting? Screening studies may give some idea about the ‘true’ prevalence. A prevalence of 5.8/10 000 (Panaiotova et al, Ultrasound Obstet Gynecol 2019; 53: 101–106) was reported with screening for Caesarean scar pregnancies. Coutinho et al (Ultrasound Obstet Gynecol 2021; 57: 91–96) reported a prevalence of 3.8/10 000 with screening for PAS in late pregnancy. In both these reports all women had either placenta previa or a low-lying placenta. In contrast, placenta previa was present in 64% and 63% of women from UK and France, respectively. In this light, one would expect a higher, rather than lower prevalence of PAS as compared to the two screening studies. One explanation could be increasing Caesarean section rate and better awareness with time.A systematic review reported high (>90%) sensitivity for the detection of PAS using ultrasound in women at high risk of PAS (D’Antonio et al, Ultrasound Obstet Gynecol 2013; 42: 509–517). The prenatal detection was disappointingly low at < 50% in both UK and France. Before we begin to berate ourselves, it is noteworthy that these are 7-12 year-old data. The current study took place between May 2010 - April 2011(UK) and November 2013 - October 2015(France).What about the differences in median blood loss? Manual removal of the placenta was attempted in fewer women in France. Even then, unplanned hysterectomy was more common in the French group. The blood loss may be lower with conservative management, but this advantage should be weighed against the uncertainty about the possibility and timing of developing major haemorrhage in the post-operative period. Moreover, it is possible that the UK series had particularly severe cases as compared to the French cohort given the significantly lower prevalence. A head-to-head comparison of the two treatment modalities has never been reported. This will necessitate a unified definition and accurate prenatal detection. Such a study would be extremely challenging given the strong views of women regarding fertility preservation and of physicians regarding ongoing uncertainty with complications and personal experience. The jury is still out on this one.