The effect of placental laterality at 20-24 gestational weeks on uterine artery doppler indices, fetal growth and preeclampsia.

BACKGROUND

This study aimed (i) to assess the potential effect of placental location on uterine artery (UtA) pulsatility index (PI) and offspring birthweight (BW), and (ii) to examine the potential association of unilaterally increased UtA PI with preeclampsia (PE) or low BW.

MATERIALS AND METHODS

This was an asynchronous cohort study of singleton pregnancies between 20 and 23 gestational weeks resulting in live birth, for whom the placental site (posterior, anterior, fundal, previa, right lateral, or left lateral) and bilateral UtA PI measurements were recorded. The effect of placental location on mean BW and UtA mean PI z-scores was assessed using -test or ANOVA and post-hoc tests, as appropriate. The UtA PI measurements were then grouped into three categories (normal mean PI; unilaterally increased PI with normal mean; increased mean PI) and we calculated the odds ratios (ORs) of unilaterally increased or increased mean PI vs. normal mean PI for PE, BW <10th centile and BW <5th centile. The independent association of placental location, UtA PI category (normal mean, unilateral increase with normal mean, increased mean PI) and UtA PI z-score with PE, BW <10th centile and BW <5th centile was then assessed using logistic regression.

RESULTS

The analysis included 5506 pregnancies. A lateral placenta was associated with higher mean PI z-score ( = .0001) and lower BW ( = .003) than non-lateral placenta. Compared with normal mean UtA PI, a unilaterally increased PI with a normal mean was associated with increased risk for PE (OR 4.3, 95%CI 1.9-9.7), BW <10th centile (OR 1.7, 95%CI 1.3-2.4) and BW <5th centile (OR 1.8, 95%CI 1.1-2.9). Similarly, increased mean UtA PI was also associated with increased risk for PE, BW <10th and BW <5th centile (OR 9.1, 95%CI 4.8-17.3; OR 4.4, 95%CI 3.5-5.7; OR 7.0, 95%CI 5.1-9.6, respectively). When assessing the independent association of placental location and UtA PI with PE and low BW, only mean UtA PI remains a significant predictor.

CONCLUSIONS

A lateral placenta is associated with a higher mean UtA PI and lower BW. Unilaterally increased UtA PI still carries a greater risk of PE and low BW than bilaterally normal PI, however this effect appears to be eventually mediated through mean UtA PI z-score, which is relatively increased in these cases.