METHODS: Women at 28-32 weeks' gestation attending antenatal clinic for routine care were screened using the Rome IV chronic constipation criterion. Eligible women were approached and consented. Participants were randomized to oral polyethylene glycol (10 g/day) or lactulose (10 g/day) for 4 weeks. A bowel movement diary was kept and outcomes using the Patient Assessment of Constipation Symptoms questionnaire (PAC-SYM), Patient Assessment of Constipation Quality of Life questionnaire (PAC-QoL) and Bristol Stool Form Scale (BSFS), which were evaluated at the start and end of the four-week period. Relative risks (RR) were determined for the coprimary outcomes of complete spontaneous bowel movement (CSBM) and PAC-SYM mean score improvement (decrease in score of >1 from the baseline).

RESULTS: A total of 4323 women underwent screening, of which 780 fulfilled the Rome IV criterion, and 360 consented to participate (180 randomized to PEG and lactulose, respectively). Data from 247 women who completed the study were analyzed. CSBM was achieved in 107/124 (86.3%) versus 102/123 (82.9%) (RR 1.04, 95% CI: 0.93-1.16, P = 0.464) for PEG and lactulose trial arms, respectively. PAC-SYM mean score improvement was 62/118 (52.5%) in the PEG arm versus 44/118 (37.3%) in the lactulose arm (RR 1.40, 95% CI: 1.05-1.88). Of secondary outcomes, a significant difference was found in favor of PEG, with respect to PAC-SYM abdominal symptoms subscale, normal stool versus loose stool consistency and side effects of vomiting and diarrhea. After controlling for parity, baseline PAC-SYM, PAC-QoL scores, characteristics different at baseline, only diarrhea and loose stools remained significant.