Correction to: One Plus One Equals Two-will that do? A trial protocol for a Swedish multicentre randomised controlled trial to evaluate a clinical practice to reduce severe perineal trauma

An amendment to this paper has been published and can be accessed via the original article.

One Plus One Equals Two-will that do? A trial protocol for a Swedish multicentre randomised controlled trial to evaluate a clinical practice to reduce severe perineal trauma {1}

Background

Severe perineal trauma sustained during childbirth is a serious complication since it can lead to both short- and long-term consequences for women. Some of the methods used to prevent perineal injuries have been evaluated in clinical trials, but there are still gaps in the evidence. A new clinical practice has been introduced, adopted by more than half of the maternity wards in Sweden with the aim of reducing severe perineal trauma. This procedure involves two midwives assisting the woman during the second stage of labour.

Methods/design

In this multicentre randomised controlled trial, 2946 women will be randomised to be assisted by one or two midwives during the second stage of labour. Women age 18–47, who plan for their first vaginal birth, with a singleton pregnancy in cephalic presentation, will be asked to participate when admitted to the maternity ward. Five maternity wards comprising 19,500 births/year in different parts of Sweden will participate in this study. The sample size is powered to demonstrate a 50% reduction (from 4.1–2.0%) in primary outcome, which is the prevalence of severe perineal trauma (3rd and 4th degree). Secondary outcomes will include maternal and neonatal outcomes, women’s experiences, midwives’ experiences of the intervention, incontinence, and pelvic floor symptoms. The primary analysis is intention to treat. Questionnaires will be sent to the women at 1 month and 1 year after the birth to assess women’s experiences, pain, incontinence, pelvic floor symptoms, sexual function, and mental health.

Discussion

It is important for care during labour and birth to be evidence based. There is a strong desire among midwives to reduce the risk of severe perineal trauma. This may lead to new strategies and practices being implemented into practice without scientific evidence. The intervention might have negative side effects or unintended consequences. On the other hand, there is a possibility of the intervention improving care for women.

Trial registration {2a}

ClinicalTrials.gov NCT03770962. Registered on 10 December 2018

Contribution of endogenous endothelin-1 to basal vascular tone during normal pregnancy and preeclampsia

OBJECTIVE

The aim of this study was to determine the physiologic role for endogenous endothelin in the regulation of vascular tone during normal pregnancy and preeclampsia. The vascular sensitivity to endothelin-1 during pregnancy was studied also.

STUDY DESIGN

Forearm blood flow was measured by venous occlusion plethysmography during intra-arterial infusion of phosphoramidon, an endothelin-converting enzyme inhibitor, for 60 minutes, which was followed by co-infusion with endothelin-1 for 30 minutes. Three groups were studied: healthy nonpregnant women, normal pregnant women, and women with preeclampsia.

RESULTS

There was a significant increase in forearm blood flow in the nonpregnant group after phosphoramidon infusion alone (73%+/-37%; P<.05). Phosphoramidon did not change forearm blood flow in pregnant subjects. Co-infusion with endothelin-1 significantly decreased forearm blood flow in both the nonpregnant and normal pregnant women (53%+/-7% and 40%+/-11%, respectively; P<.01). No response to endothelin-1 was found among women with preeclampsia.

CONCLUSION

The vascular sensitivity to endothelin-1 is not altered during normal pregnancy in contrast to preeclamptic pregnancy, where no effect of endothelin-1 was seen. Reduced endothelin dependence during pregnancy might be one mechanism behind the fall in peripheral vascular resistance.

The role of endogenous endothelin in the regulation of uteroplacental and renal blood flow during pregnancy in conscious rats

Advancing pregnancy is characterized by a ten-fold increase in uterine blood flow and a 50 per cent increase in renal blood flow. To evaluate the involvement of endogenous endothelin (ET) in these haemodynamic changes the effect of bosentan, an ETA/B receptor antagonist, on uteroplacental and renal blood flow was studied in awake pregnant Sprague-Dawley rats. Regional blood flows were measured using microsphere technique immediately prior to and 30 min after bosentan administration (20 mg/kg i.v.). Four groups of animals (term: 23 days) were included: bosentan was administered to ten rats at gestation day (GD) 19 and nine at GD 20-21. In addition, four rats at GD 19 and five animals at GD 20-21 received saline and served as control groups. Basal placental blood flow increased significantly from 19 days' gestation to 20-21 days. Basal myometrial blood flow did not change with gestational age. At gestation day 19 bosentan increased placental and myometrial blood flow significantly (80 per cent and 43 per cent, respectively, P<0.05). This effect was not observed at gestation days 20-21. Renal blood flow did not change in response to bosentan at GD 19 but decreased by 20 per cent at GD 20-21 (P<0.01). In conclusion, in the awake pregnant rat there is a significant endogenous ET dependent vasoconstrictor tone in the uteroplacental vessels that diminishes towards term. We speculate that this change in responsiveness to endogenous ET contribute to the increase in placental blood flow in late gestation.