Precise mid-trimester placenta localisation: Does it predict adverse outcomes?

• Published in: Australian & New Zealand journal of obstetrics & gynaecology 2012-04, Vol.52 (2), p.156-160
• Main Authors: Robinson, Alice J., Muller, Peter R., Allan, Richard, Ross, Richard, Baghurst, Peter A., Keirse, Marc J.N.C.
• Format: Article
• Language: English
• Subjects: Adult; Female; Humans; mid-trimester; placenta; Placenta - diagnostic imaging; placenta praevia; Placenta Previa - diagnostic imaging; Pregnancy; pregnancy outcome; Pregnancy Outcome - epidemiology; Pregnancy Trimester, Second; Prospective Studies; Ultrasonography, Prenatal; ultrasound; vasa praevia; Young Adult
• ISSN: 0004-8666; 1479-828X
• DOI: 10.1111/j.1479-828X.2012.01416.x

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