Oligohydramnios: should it be considered a risk factor for developmental dysplasia of the hip?

Breech, family history, first born and female sex are the main risk factors described for developmental dysplasia of the hip (DDH). Foot abnormalities and oligohydramnios have also been listed. Recent studies have discredited torticollis, multiple gestation pregnancy, mode of delivery and prematurity as risk factors. Definition of oligohydramnios in the literature is inconsistent. Our aim was to investigate the term oligohydramnios and evaluate whether it should be considered a risk factor for DDH. All live births in our institution between 2001 and 2014 were included. We identified all pregnancies classed as reduced amniotic fluid (AF) or oligohydramnios over that period. Data on DDH, breech presentation, female sex and positive family history were collected. The significance level was set to 5%. We identified 73 990 live births, 3408 pregnancies were classed as reduced AF or oligohydramnios. The incidence of DDH (Graf type IIb and higher) was 1: 1000 (75 babies, 18 bilateral). Oligohydramnios/reduced AF was found in 12 (16%) DDH babies. Breech presentation was found in 24 (32%), positive family history in 19 (25%) and female sex in 71 (94.7%). Oligohydramnios was found to be associated with a higher odds ratio (OR) for DDH [OR = 3.9, 95% confidence interval (CI): 2.1-7.3] as were breech presentation (OR = 10.6, 95% CI: 6.5-17.1) and female sex (OR = 19.1, 95% CI: 7-52.4). All examined risk factors showed statistical significance (P < 0.05). A regression analysis was performed to control for interactions and confounding factors and confirmed the findings. On the basis of our findings the diagnosis of reduced AF/oligohydramnios in consecutive antenatal sonographic scans should be regarded as an independent risk factor for DDH and be considered in any future studies regarding DDH. Level of evidence: Level IV: Case series.