EP17.60: The association of placental‐fetal ratio with pregnancy duration

To explore the association between placental-fetal volume ratio (placental-fetal ratio) at gestational week 27 with time to spontaneous delivery. For comparison, we studied the association of fetal and of placental size with time to delivery. We included 100 pregnancies in a follow-up study from gestational week 27 until spontaneous delivery. Placental and fetal volume were measured by magnetic resonance imaging (MRI), and the association of placental-fetal ratio (placental volume/fetal volume) with delivery after spontaneous onset of labour was estimated as hazard ratios (HR) by applying Cox regression models. HR of 1.0 indicates no association. Pregnancies with deliveries after planned Caesarean section or induced labour provided follow-up time until these events. Mean placental volume was 532 cm3 (SD 136 cm3), while fetal volume was 961 cm3 (SD 112 cm3). This yielded a mean placental-fetal ratio of 0.55 (SD 0.12). The HR of spontaneous delivery decreased by increasing placental-fetal ratio (HR 0.013 (95% CI 0.001 – 0.121, p < 0.001)), indicating a longer duration of pregnancy with higher placental-fetal ratio. The HR of spontaneous delivery decreased also by increasing placental size (HR 0.997 (CI 0.995 – 0.999, p = 0.006)). For the fetal size, we estimated no association (HR 1.001 (CI 0.999 – 1.003, p = 0.189)). Our findings suggest that the placental-fetal ratio at gestational week 27 may be an indicator of the remaining time of pregnancy until onset of spontaneous labour. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.