What is the issue?
Can aspirin be given to women who experience perineal pain following childbirth to relieve the pain without causing side effects for either women or their babies?
Why is this important?
Many women experience pain in the perineum (the area between the vagina and anus) following childbirth. The perineum may be bruised or torn during childbirth, or a cut made for the baby to be born (an episiotomy). After childbirth, perineal pain can interfere with women's ability to care for their newborns and establish breastfeeding. If perineal pain is not relieved effectively, longer-term problems for women may include painful sexual intercourse, pelvic floor problems resulting in incontinence, prolapse or chronic perineal pain. Aspirin may be given to women who have perineal pain after childbirth, but its effectiveness and safety had not been assessed in a systematic review. This is part of a series of reviews looking at drugs to help relieve perineal pain in first few weeks after childbirth.
What evidence did we find?
We searched for evidence on 31 May 2016, and included 17 studies involving 1132 women published between 1967 and 1997. All women had perineal pain following an episiotomy (usually within 48 hours after birth) and were not breastfeeding. The women received either aspirin (doses ranging from 300 mg to 1200 mg) or fake pills (placebo), by mouth. The studies were assessed as low- or very low-quality evidence. Two trials did not contribute any data for analyses.
More women had adequate pain relief at four to eight hours after taking aspirin compared with women who received placebo (low-quality evidence). Women were less likely to need additional pain relief at four to eight hours after taking aspirin (very low-quality evidence). There was no difference in adverse effects for women in the four to eight hours after administration (very low-quality evidence).
We found no clear differences in effect for women who received 300 mg versus 600 mg aspirin (1 trial), 600 mg versus 1200 mg aspirin (2 trials), or 300 mg versus 1200 mg (1 trial) for adequate pain relief, the need for additional pain relief, or adverse effects for the mother.
No studies reported on adverse effects of aspirin for the baby, or other outcomes we planned to assess: prolonged hospital stay or readmission to hospital due to perineal pain; perineal pain six weeks after childbirth, women's views, or postpartum depression.
What does this mean?
A single dose of aspirin may help with perineal pain following episiotomy for women who are not breastfeeding, when measured four to eight hours after administration. Breast milk is widely accepted as the best food for infants and it is recommended that where possible, mothers start breastfeeding within one hour of birth, and breastfeed for the first six months of their infant's life. We found no information to assess the effects of aspirin for women who are breastfeeding, but it is known that aspirin can be transferred into the breast milk.
We found low-quality evidence to suggest that single dose aspirin compared with placebo can increase pain relief in women with perineal pain post-episiotomy. Very low-quality evidence also suggested that aspirin can reduce the need for additional analgesia, without increasing maternal adverse effects. Evidence was downgraded based on study limitations (risk of bias), imprecision, and publication bias or both. RCTs excluded breastfeeding women so there is no evidence to assess the effects of aspirin on neonatal adverse effects or breastfeeding.
With international guidance recommending mothers initiate breastfeeding within one hour of birth, and exclusively breastfeed for the first six months, the evidence from this review is not applicable to current recommended best practice. Aspirin may be considered for use in non-breastfeeding women with post-episiotomy perineal pain. Although formal assessment was beyond the remit of this review, current guidance suggests that other analgesic drugs (including paracetamol) should be considered first for postpartum perineal pain. Such agents are the focus of other reviews in this series on drugs for perineal pain in the early postpartum period. It is considered most likely that if RCTs are conducted in the future they could compare aspirin with other pain relievers. Future RCTs should be designed to ensure high methodological quality, and address gaps in the evidence, such as the secondary outcomes established for this review. Current research has focused on women with post-episiotomy pain, future RCTs could be extended to women with perineal pain associated with spontaneous tears or operative birth.
Perineal trauma (due to spontaneous tears, surgical incision (episiotomy) or in association with operative vaginal birth) is common after vaginal birth, and is often associated with postpartum perineal pain. Birth over an intact perineum may also lead to perineal pain. There are adverse health consequences associated with perineal pain for the women and their babies in the short- and long-term, and the pain may interfere with newborn care and the establishment of breastfeeding. Aspirin has been used in the management of postpartum perineal pain and its effectiveness and safety should be assessed.
To determine the efficacy of a single dose of aspirin (acetylsalicylic acid), including at different doses, in the relief of acute postpartum perineal pain.
Randomised controlled trials (RCTs) assessing single dose aspirin compared with placebo, no treatment, a different dose of aspirin, or single dose paracetamol/acetaminophen for women with perineal pain in the early postpartum period. We planned to include cluster-RCTs but none were identified. Quasi-RCTs and cross-over studies were not eligible for inclusion in this review.
Two review authors independently assessed study eligibility, extracted data and assessed the risk of bias of the included RCTs. Data were checked for accuracy. The quality of the evidence for the main comparison (aspirin versus placebo) was assessed using the GRADE approach.
We included 17 RCTs, with 16 involving 1132 women randomised to aspirin or placebo (one RCT did not report numbers of women). Two RCTs (of 16) did not contribute data to review meta-analyses. All women had perineal pain post-episiotomy, and were not breastfeeding. Studies were published between 1967 and 1997, and the risk of bias was often unclear due to poor reporting.
We included four comparisons: aspirin versus placebo (data from 15 RCTs); 300 mg versus 600 mg aspirin (1 RCT); 600 mg versus 1200 mg aspirin (2 RCTs); and 300 mg versus 1200 mg aspirin (1 RCT).
Aspirin versus placebo
More women who received aspirin experienced adequate pain relief compared with women who received placebo over four to eight hours after administration (risk ratio (RR) 2.03, 95% confidence intervals (CI) 1.69 to 2.42; 13 RCTs, 1001 women; low-quality evidence). Women who received aspirin were less likely to need additional pain relief over four to eight hours after administration (RR 0.25, 95% CI 0.17 to 0.37; 10 RCTs, 744 women; very low-quality evidence). There was no difference in maternal adverse effects over four to eight hours post-administration (RR 1.08, 95% CI 0.57 to 2.06; 14 RCTs, 1067 women; very low-quality evidence). Subgroup analyses based on dose did not reveal any clear subgroup differences.
There was no clear difference over four hours after administration between 300 mg and 600 mg aspirin for adequate pain relief (RR 0.82, 95% CI 0.36 to 1.86; 1 RCT, 81 women) or need for additional pain relief (RR 0.68, 95% CI 0.12 to 3.88; 1 RCT, 81 women). There were no maternal adverse effects in either aspirin group.
There was no clear difference over four to eight hours after administration between 600 mg and 1200 mg aspirin for adequate pain relief (RR 0.85, 95% CI 0.52 to 1.39; 2 RCTs, 121 women), need for additional pain relief (RR 1.32, 95% CI 0.30 to 5.68; 2 RCTs, 121 women), or maternal adverse effects (RR 3.00, 95% CI 0.13 to 69.52; 2 RCTs, 121 women).
There was no clear difference over four hours after administration between 300 mg and 1200 mg aspirin for adequate pain relief (RR 0.62, 95% CI 0.29 to 1.32; 1 RCT, 80 women) or need for additional pain relief (RR 2.00, 95% CI 0.19 to 21.18; 1 RCT, 80 women). There were no maternal adverse effects in either aspirin group.
None of the included RCTs reported on neonatal adverse effects.
No studies reported on secondary review outcomes: prolonged hospitalisation due to perineal pain; re-hospitalisation due to perineal pain; fully breastfeeding at discharge; mixed feeding at discharge; fully breastfeeding at six weeks; mixed feeding at six weeks; perineal pain at six weeks; maternal views; maternal postpartum depression.