Introducing salt solution into the womb (amnioinfusion) to reduce complications associated with pregnancy fluid and sac infection (chorioamnionitis)

What is the issue?

Chrioamnionitis is an infection of the fluid and sac surrounding the baby in the womb. This is usually managed with antibiotics and by delivering the baby. An additional method suggested is to infuse a salt solution into the womb either via a needle through the mother's abdomen (transabdominal) or a catheter via the mother's vagina (transcervical). The theory is that this may have a beneficial flushing or diluting effect on the infecting organisms.

Why is this important?

Chorioamnionitis may lead to serious complications such as infection of the baby or of the mother. Any effective additional method of treatment would be useful.

What evidence did we find?

We searched for evidence on 6 July 2016 and only found one randomised controlled trial (which reported data from a total of 34 women). Data were available for 17 women who received transcervical amnioinfusion and 17 women who did not. All of the women received paracetamol and antibiotics and they also had a special type of catheter inserted into the cervix to measure information about their contractions (i.e. how often the contractions occur, how long they lasted and how strong they were).

The trial was considered to be at a high risk of bias overall, due to small numbers, inconsistency in the reporting and lack of information on blinding. Given the small sample size, the power to show differences between the two groups was thus small, and no differences were shown for the review's main outcomes: infection of the mother's womb after the birth (low-quality evidence); infection of the baby (low-quality evidence); caesarean section (low-quality evidence); duration of antibiotic treatment; nor duration of hospital stay. The mother's temperature at delivery, which was not a pre-defined outcome for our review, was lower in the women who received amnioinfusion, by 0.38 °C (with a likely range of 0.74 lower to 0.02 lower). The outcome death or severe illness in the baby was not reported, nor did the study report on the number of babies with a low Apgar score after they were born (a low Apgar score could indicate that the baby is in need of medical attention). Similarly, the majority of other outcomes listed in this review were not reported in the included study.

We did not identify any studies that looked at introducing the solution through the mother's abdomen (transabdominal route).

What does this mean?

There is not enough evidence to support the use of amnioinfusion for chorioamnionitis in clinical practice. We suggest that the reduction in temperature may have been in part due to a direct cooling effect of the infused fluid, and that further research is justified to determine whether such a cooling effect may be beneficial for the baby.

Further randomised controlled trials are needed in this area. Future trials should compare transabdominal or transcervical amnioinfusion with no amnioinfusion for women with pregnancy fluid and sac infection (chorioamnionitis) and report on important outcomes listed in this review.

Authors' conclusions: 

There is insufficient evidence to fully evaluate the effectiveness of using transcervical amnioinfusion for chorioamnionitis and to assess the safety of this intervention or women’s satisfaction. We did not identify any trials that used transabdominal amnioinfusion. The evidence in this review can neither support nor refute the use of transcervical amnioinfusion outside of clinical trials. We included one small study that reported on a limited number of outcomes of interest in this review. The numbers included in this review are too small for meaningful assessment of substantive outcomes, where reported. For those outcomes we assessed using GRADE (postpartum endometritis, neonatal infection, and caesarean section), we downgraded the quality of the evidence to low - with downgrading decisions based on small numbers and a lack of information on blinding. The included study did not report on this review's other primary outcome (perinatal death or severe morbidity).

The reduction in pyrexia, though not a pre-specified outcome of this review, may be of relevance in terms of benefits to the fetus of reduced exposure to heat. We postulate that the temperature reduction found may be a direct cooling effect of amnioinfusion with room temperature fluid, rather than reduction of infection. Larger trials are needed to confirm and extend the findings of the trial reviewed here. These should be randomised controlled trials; participants, women with chorioamnionitis; interventions, amnioinfusion; comparisons, no amnioinfusion; outcomes, maternal and perinatal outcomes including neurodevelopmental measures.

Further research is justified to determine possible benefits or risks of amnioinfusion for chorioamnionitis, and to investigate possible benefits of reducing temperature in fetuses considered at risk of neurological damage. Research should include randomised trials to examine transcervical or transabdominal amnioinfusion compared with no infusion for chorioamnionitis and examine outcomes listed in the methods of this review.

Read the full abstract...
Background: 

Chorioamnionitis is a leading cause of perinatal morbidity and mortality. Amnioinfusion aims at reducing the adverse effects of chorioamnionitis by dilution of the infective organisms or by an anti-microbial effect of the fluid infused.

Objectives: 

The objective of this review was to determine the effect of amnioinfusion on clinical and sub-clinical chorioamnionitis, fetal well-being, fetal heart rate characteristics and perinatal and maternal morbidity and mortality.

Search strategy: 

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (6 July 2016), PubMed, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (6 July 2016) and reference lists of retrieved studies.

Selection criteria: 

Randomised clinical trials (RCTs) of amnioinfusion (treatment group) versus no amnioinfusion in women with chorioamnionitis.

We would have also considered trials comparing amnioinfusion with sham amnioinfusion; different types or volumes of amnioinfusion fluid but none were identified.

Cluster-RCTs and quasi-RCTs were eligible for inclusion but none were identified. We identified one study published in abstract form but it did not contain any numerical data and has therefore been excluded. Studies using a cross-over design are not an appropriate study design and thus were not eligible for inclusion in this review.

Data collection and analysis: 

Two review authors independently assessed potential studies for inclusion and assessed trial quality. Both review authors independently extracted data and data were checked for accuracy.

Main results: 

We included one small trial (with data from 34 participants) comparing transcervical amnioinfusion with no amnioinfusion. The trial was considered to be at a high risk of bias overall, due to small numbers, inconsistency in the reporting and lack of information on blinding. Meta-analysis was not possible. Transcervical amnioinfusion was with room temperature saline at 10 mL per minute for 60 minutes, then 3 mL per minute until delivery versus no amnioinfusion. All women received intrauterine pressure catheter, acetaminophen and antibiotics (ampicillin or, if receiving Group B beta streptococcal prophylaxis, penicillin and gentamycin). We did not identify any trials that used transabdominal amnioinfusion.

Compared to no amnioinfusion, transcervical amnioinfusion had no clear effect on the incidence of postpartum endometritis (risk ratio (RR) 1.50, 95% confidence interval (CI) 0.29 to 7.87; absolute risk 176/1000 (95% CI 34 to 96) versus 118/1000; low-quality evidence). Nor was there a clear effect in the incidence of neonatal infection (RR 3.00, 95% CI 0.13 to 68.84; absolute risk 0/1000 (95% CI 0 to 0) versus 0/1000; low-quality evidence). The outcome of perinatal death or severe morbidity (such as neonatal encephalopathy, intraventricular haemorrhage, admission to intensive/high care) was not reported in the included trial.

In terms of this review's secondary outcomes, the rate of caesarean section was the same in both groups (RR 1.00, 95% CI 0.35 to 2.83; absolute risk 294/1000 (95% CI 103 to 832) versus 294/1000; low-quality evidence). There was no clear difference in the duration of maternal antibiotic treatment between the amnioinfusion and no amnioinfusion control group (mean difference (MD) 16 hours, 95% CI -1.75 to 33.75); nor in the duration of hospitalisation (MD 3.00 hours, 95% CI -15.49 to 21.49). The study did not report any information about how many babies had a low Apgar score at five minutes after birth.

Women in the amnioinfusion group had a lower temperature at delivery compared to women in the control group (MD -0.38°C, 95% CI -0.74 to -0.02) but this outcome was not pre-specified in the protocol for this review.

The majority of this review's secondary outcomes were not reported in the included study.

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