Among 1876 women who responded to the survey, 355 (19%) reported using domperidone. Of the women who reported domperidone use, most (n = 314, 88%) used it in combination with other galactagogues, and only 41 women (12%) reported using domperidone alone. The characteristics of women who reported taking domperidone and those who did not are listed in Table 1. Overall, domperidone use was significantly higher in women who were primiparous, delivered prematurely, delivered by caesarean section, reported self-perceived low milk supply, and worked with a lactation consultant. Compared with those who didn't take domperidone, those who took domperidone reported higher levels of perceived safety for maternal health (mean ± standard deviation 3.9 ± 1.2 vs 3.5 ± 1.0; P < 0.001) as well as infant health (infant mean ± standard deviation 3.9 ± 1.2 vs 3.4 ± 1.0: P < 0.001).

Participants reported that the majority of prescriptions for domperidone were provided by general practitioners (n = 271, 76%), followed by obstetricians (n = 72, 20%), midwives (n = 41, 12%), and neonatologists (n = 19, 5%). Approximately one in six (16%) women reported receiving a domperidone prescription from multiple prescribers.

Maximum reported doses of domperidone used ranged from 20 mg/day to 160 mg/day. Half (n = 178, 50%) of women reported using a dose of 30 mg/day or less, 44% (n = 155) reported using a dose between 31 and 60 mg/day, and 6% (n = 22) reported using a dose greater than 61 mg/day. Maternal characteristics of each dose category are reported in Supplementary Table 1.

Of all domperidone use, nearly 20% (n = 67) of women started using it in the first 7 days postpartum, and a further 38% (n = 134) started using it in the first four weeks postpartum. Women who started domperidone use earlier were more likely to report using higher maximum doses (see Supplementary Table 2).

The duration of use varied from one week to greater than one year, with a median duration of 6 weeks (Interquartile range [IQR] 3 – 16 weeks; Supplementary Table 3). For women who were continuing domperidone use at the time of survey completion, 90% (n = 73/81) had been using domperidone for two or more weeks, where the median duration of use was 11 weeks (IQR 5 – 20). Duration of use was considerably longer for those reporting doses ≥ 61 mg/day (median 20 weeks, IQR 12 – 52 weeks; P < 0.001) compared to doses of ≤ 30 mg/day (median 4.5 weeks, IQR 2 – 11 weeks) and 31 – 60 mg/day (median 10 weeks, IQR 4 – 20 weeks).

Side effects are reported in Table 2. Nearly half of all women using domperidone reported side effects (n = 172, 48%), with 9% (n = 31) of all women using domperidone ceasing use due to side effects. Of those experiencing side effects, the most common side effect was weight gain (25%, n = 88), followed by headaches (17%, n = 59) and dry mouth (13%, n = 47). Thirteen (4%) women reported experiencing heart palpitations/racing heart with domperidone use. Of the women reporting side effects, 47% (n = 80) experienced two or more side effects. The frequency of stopping use because of side effects was highest in those reporting headaches (58%, n = 18), followed by weight gain (48%, n = 15) and dry mouth (28%, n = 9). There was no difference in cessation rates due to side effects between women with perceived low supply or no perceived supply problems (P < 0.699). Higher doses were associated with higher rates of side effects (≤ 30 mg/day, 38.2%; 31 – ≤ 60 mg/day, 48.4%, ≥ 60 mg/day 72.7%; P < 0.004, Chi2). The likelihood of medication cessation due to side effects increased as the dose increased (≤ 30 mg/day, 7.9%, n = 14; 31 – ≤ 60 mg/day, 9.0%, n = 14; ≥ 60 mg/day 13.6%, n = 3; P < 0.000). A linear trend was observed between high perceived effectiveness and lower likelihood of women stopping domperidone due to side effects (P < 0.008).

Forty-five percent of women felt domperidone was 'very' or 'extremely effective', 47% felt it was ‘slightly’ to ‘moderately’ effective, with only 8% reporting it was 'not at all effective'. Perceived effectiveness was not significantly different for women based on parity, method of birth, gestation at birth, or timing of commencement of domperidone (Table 3). Perceived effectiveness of domperidone was higher among those taking doses ≥ 61 mg/day, but the differences were not statistically significant (≤ 30 mg/day; mean ± standard deviation 3.3 ± 1.2, n = 178; 31 – 60 mg/day 3.2 ± 1.2, n = 155; ≥ 61 mg/day 4.2 ± 0.9 n = 22 P < 0.310, One-way ANOVA). Perceived effectiveness of domperidone was lower among those reporting a requirement to use infant formula due to supply difficulties, compared with those who did not require infant formula (3.2 ± 1.2 vs 3.6 ± 1.1; P < 0.001).

Seventy-eight percent (n = 277) of women responded that they would use domperidone again. Eighty-two percent (n = 290) of women reported that they would recommend domperidone to a friend, whereas 18% (n = 62) would not recommend it. the most common reasons for not recommending domperidone were that it did not work (55%, n = 34), and because of side effects (40%, n = 25). Other reasons for not recommending domperidone use included that is was too expensive (3%, n = 2), and ‘other’ (13%, n = 8). The likelihood of recommendation domperidone to a friend increased significantly with higher perceived effectiveness (P < 0.000). Women who ceased domperidone use due to side effects were also less likely to recommend domperidone to a friend (P < 0.000).