Precise mid-trimester placenta localisation: does it predict adverse outcomes?
Date
2012
Authors
Robinson, A.
Muller, P.
Allan, R.
Ross, R.
Baghurst, P.
Keirse, M.
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Journal article
Citation
Australian and New Zealand Journal of Obstetrics and Gynaecology, 2012; 52(2):156-160
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Alice J. Robinson, Peter R. Muller, Richard Allan, Richard Ross, Peter A. Baghurst and Marc J.N.C. Keirse
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Abstract
BACKGROUND: A low-lying placenta detected at the mid-pregnancy ultrasound is commonly reported to warn against potential morbidity associated with placenta praevia. There is no information on what distance away from the internal cervical os is safe. AIMS: We examined whether a low-lying placenta not overlapping the cervical os in the second trimester increases the risk of obstetric complications and whether there is a cut-off point at which that increase occurs. METHODS: Adverse perinatal outcomes were examined prospectively in a cohort of women with a placenta 0–30 mm from the internal cervical os (low-lying) at the routine mid-trimester ultrasound and compared to those with a placenta further away. Two composite outcomes of major and minor adverse events were predefined as primary outcome measures, requiring a sample size of 480 women with a low-lying placenta. Chi-square and Fisher’s exact tests were used for statistical analysis. RESULTS: In 1662 pregnancies (low-lying: n = 484; normal: n = 1178), there was no increase in composite adverse outcomes with a low-lying placenta and no cut-off distance within 30 mm from the cervical os at which risks increased. Postpartum haemorrhage >1000 mL was more frequent with a low-lying placenta (7.6% vs 4.7%, P < 0.05). CONCLUSIONS: Women with a low-lying placenta, not overlapping the cervical os, in mid-pregnancy are at no higher risk of adverse outcomes than those with a normally located placenta, except postpartum haemorrhage. This suggests that the high-risk label can be removed from pregnancies with a low-lying placenta not overlapping the cervical os in midpregnancy, reducing anxiety and resource utilisation.
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© 2012 The Authors ANZJOG © 2012 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists