Unilaterally increased uterine artery resistance, placental location and pregnancy outcome

To evaluate the outcome of pregnancies with second trimester unilaterally increased uterine artery resistance.

Between January 2007 and December 2009 all low-risk patients with unilateral increase of uterine artery pulsatility index (PI) but normal mean pulsatility at 20-22 weeks of gestation were included in the study group. Among these, cases with central placenta (group A) were distinguished from those with lateral placenta (group B). A control group was selected among patients with bilaterally normal uterine artery PI. Pregnancy outcome was considered for all cases and compared with controls.

In the study period, 131 patients with second trimester unilaterally increased uterine artery PI were identified. Placental location was central in 67 (51.1%) patients (group A) and lateral in 64 (48.9%) patients (group B). In the study group (n=131) compared to controls (n=131), mean gestational age at delivery (38.9 ± 1.4 weeks vs. 38.8 ± 1.6 weeks; p=0.43), mean birth weight (3251 ± 445 vs. 3276 ± 388; p=0.63), Z-score of birth weight (-0.17 ± 0.87 SD vs. -0.04 ± 0.69 SD; p=0.19), occurrence of pre-eclampsia (4/131 vs. 3/131; p=1), low birth weight (7/131 vs. 7/131; p=1) and caesarean section due to fetal distress (9/131 vs. 6/131; p=0.5) were not significantly different. The same variables were compared within the study group between cases with central (group A) vs. lateral (group B) placenta and none of them was significantly different.

Patients with unilaterally abnormal uterine artery pulsatility, but normal mean PI, do not seem at increased risk for obstetric and perinatal complications, irrespectively of placental location.