Evidence
This page contains a snapshot of featured content which highlights evidence addressing key clinical questions including areas of uncertainty. Please see the main topic reference list for details of all sources underpinning this topic.
BMJ Best Practice evidence tables
Evidence tables provide easily navigated layers of evidence in the context of specific clinical questions, using GRADE and a BMJ Best Practice Effectiveness rating. Follow the links at the bottom of the table, which go to the related evidence score in the main topic text, providing additional context for the clinical question. Find out more about our evidence tables.
This table is a summary of the analysis reported in a guideline (underpinned by a systematic review) that focuses on the above important clinical question.
Confidence in the evidence is very low or low where GRADE has been performed and there may be no difference in effectiveness between the intervention and comparison for key outcomes. However, this is uncertain and new evidence could change this in the future.
Population: Pregnant women with pre-eclampsia
Intervention: Outpatient management
Comparison: Inpatient management
| Outcome | Effectiveness (BMJ rating)? | Confidence in evidence (GRADE)? |
|---|---|---|
Stillbirth | No statistically significant difference | Very Low |
Small for gestational age (SGA) | Favours intervention ᵃ | Very Low |
Birth weight | Favours intervention ᵃ | Very Low |
Gestational age at birth (weeks) | Favours intervention ᵃ | Low |
Admission to neonatal unit | No statistically significant difference | Very Low |
Haemolysis, elevated liver function tests and low platelets (HELLP) | See note ᵇ | Low |
Placental abruption | No statistically significant difference | Very Low |
Mode of birth (C-section) | No statistically significant difference | Very Low |
Recommendations as stated in the source guideline The guideline committee did not feel this evidence was sufficiently robust to make recommendations; see Note section below. However, they did make recommendations to offer admission to hospital according to various criteria (based on clinical expertise and on evidence on validated risk prediction models). See guideline for more details.
Note Results are based on a single retrospective cohort study of 365 women; participants had chronic hypertension with superimposed pre-eclampsia only. ᵃ Even though outpatient management reduced the number of babies who were small for gestational age, and also increased birth weight and gestational age at birth, study participants were admitted at their doctor's discretion. This seems to have resulted in the admission of women who were more ill or more at risk, leading to inpatients giving birth to babies who were smaller for gestational age, with a decreased birth weight and gestational age at birth. ᵇ There were no occurrences of HELLP syndrome in either treatment group.
This evidence table is related to the following section/s:
This table is a summary of the analysis reported in a guideline (underpinned by a systematic review) that focuses on the above important clinical question.
Confidence in the evidence is very low or low where GRADE has been performed and there may be no difference in effectiveness between the intervention and comparison for key outcomes. However, this is uncertain and new evidence could change this in the future.
Population: Pregnant women with pre-eclampsia
Intervention: Labetalol, nifedipine, nicardipine, methyldopa, or hydralazine
Comparison: Each other
| Outcome | Effectiveness (BMJ rating)? | Confidence in evidence (GRADE)? |
|---|---|---|
Intravenous labetalol versus oral nifedipine | ||
Neonatal mortality | No statistically significant difference | Very Low |
Birth weight | No statistically significant difference | Very Low |
Gestational age at birth (weeks) | No statistically significant difference | Very Low |
Minutes needed to achieve effective control of BP ᵃ | Favours intervention | Very Low |
Eclampsia or Haemolysis, elevated liver enzymes, low platelet count (HELLP) | No statistically significant difference | Very Low |
Intravenous labetalol versus intravenous nicardipine | ||
Minutes needed to achieve effective control of blood pressure (follow-up mean 1 hour) | No statistically significant difference | Low |
Labetalol versus methyldopa ᵇ | ||
Blood pressure control: Mean Arterial Pressure (MAP) (follow-up mean 7 days) | Favours intervention | Very Low |
Onset of labour (induction) (follow-up mean 7 days) | No statistically significant difference | Very Low |
Intravenous labetalol versus intravenous hydralazine | ||
Stillbirth (follow-up mean 2 hours) | No statistically significant difference | Very Low |
Neonatal death up to 7 days ᵃ | No statistically significant difference | Very Low |
Small for gestational age (SGA) | No statistically significant difference | Very Low |
Severe hypertension | No statistically significant difference | Very Low |
Eclampsia | See note ᶜ | Moderate |
HELLP | No statistically significant difference | Very Low |
Placental abruption | No statistically significant difference | Moderate |
Mode of birth (caesarean section) ᵃ | No statistically significant difference | Very Low |
Maternal death | See note ᶜ | Moderate |
Intravenous hydralazine versus oral nifedipine | ||
Stillbirth | No statistically significant difference | Very Low |
Neonatal death up to 7 days | No statistically significant difference | Very Low |
Small for Gestational Age (SGA) | No statistically significant difference | Moderate |
Blood pressure control: minutes needed to achieve effective control of BP ᵃ | No statistically significant difference | Very Low |
Severe hypertension (follow-up mean 2.05 weeks) ᵃ | Favours comparison | Very Low |
Eclampsia (follow-up mean 2.05 weeks) | See note ᶜ | Low |
Placental abruption, onset of labour (induction), or mode of birth (caesarean section) | No statistically significant difference | Very Low |
Recommendations as stated in the source guideline The guideline committee noted that there was not enough evidence to recommend one treatment over another. The committee therefore adopted a previous recommendation which states that labetalol should be used as first-line treatment since it is licenced for use in pregnancy, with nifedipine and methyldopa as alternatives.
Note The guideline categorised studies on ‘acute’ management as those including care of women with sudden, uncontrolled hypertension, very high blood pressure levels, or with acute symptoms of pre-eclampsia (headache, visual disturbance, upper abdominal pain). ᵃ The guideline also reported results for this outcome by gestational age, hypertension status, and setting, which did not affect the overall rating in this table. Please see the guideline evidence document for more details. ᵇ The report includes dose and frequency of administration, but no route is reported for either drug. ᶜ No incidents of this outcome occurred in either group.
This evidence table is related to the following section/s:
This table is a summary of the analysis reported in a guideline (underpinned by a systematic review) that focuses on the above important clinical question.
Confidence in the evidence is very low or low where GRADE has been performed and the intervention may be more effective/beneficial than the comparison for key outcomes. However, this is uncertain and new evidence could change this in the future.
Population: Pregnant women with pre-eclampsia
Intervention: Labetalol ᵃ
Comparison: No intervention
| Outcome | Effectiveness (BMJ rating)? | Confidence in evidence (GRADE)? |
|---|---|---|
Stillbirth | See note ᵇ | Moderate |
Neonatal death up to 7 days | No statistically significant difference | Very Low |
Small for gestational age (SGA) | No statistically significant difference ᶜ | Low |
Birth weight (grams) | No statistically significant difference | Moderate |
Gestational age at birth (weeks) | No statistically significant difference | Moderate |
Admission to neonatal unit | No statistically significant difference | Very Low |
Severe hypertension (maternal) | Favours intervention | Low |
Placental abruption | No statistically significant difference | Very Low |
Mode of birth (caesarean section) | No statistically significant difference | Low |
Recommendations as stated in the source guideline The guideline committee did not explicitly make a recommendation relating to labetalol versus no intervention, but did note that while there is some evidence for the benefit of labetalol, nifedipine, and methyldopa on maternal blood pressure, there is not enough to recommend one treatment over another. The committee has therefore adopted a previous recommendation which states that labetalol should be used as first-line treatment since it is licenced for use in pregnancy, with nifedipine and methyldopa as alternatives. The choice of nifedipine or methyldopa should be based on any pre-existing treatment, side-effect profiles, risks (including foetal effects), and the woman's preference.
Note The overall rating in this table reflects those outcomes which the guideline committee classed as critical (stillbirth; neonatal death; small for gestational age [babies], and severe hypertension [mothers]). The other outcomes in this table have been classed as important by the guideline committee. The guideline categorised studies on ‘acute’ management as those including care of women with sudden, uncontrolled hypertension, very high blood pressure levels, or with acute symptoms of pre-eclampsia (headache, visual disturbance, upper abdominal pain). ᵃ Route of administration not reported. ᵇ There were no stillbirths in either group. ᶜ The guideline reported that the increased numbers of SGA babies born to women taking labetalol compared with no intervention may be a clinically important increase, although not statistically significant and there was uncertainty around the estimate.
This evidence table is related to the following section/s:
This table is a summary of the analysis reported in a guideline (underpinned by a systematic review) that focuses on the above important clinical question.
Confidence in the evidence is very low or low where GRADE has been performed and the intervention may be more effective/beneficial than the comparison for key outcomes. However, this is uncertain and new evidence could change this in the future.
Population: Pregnant women with pre-eclampsia
Intervention: Methyldopa
Comparison: No treatment
| Outcome | Effectiveness (BMJ rating)? | Confidence in evidence (GRADE)? |
|---|---|---|
Perinatal death | No statistically significant difference | Very Low |
Control of blood pressure: systolic BP (maternal) | Favours intervention | Very Low |
Control of blood pressure: diastolic BP (maternal) | No statistically significant difference | Very Low |
Eclampsia | No statistically significant difference | Very Low |
Mode of birth (caesarean section) | No statistically significant difference | Very Low |
Recommendations as stated in the source guideline The guideline committee noted that while there is some evidence for the benefit of methyldopa, nifedipine, and labetalol on maternal blood pressure, there is not enough to recommend one treatment over another. The committee therefore adopted a previous recommendation which states that labetalol should be used as first-line treatment since it is licenced for use in pregnancy, with nifedipine and methyldopa as alternatives.
Note The overall rating in this table reflects those outcomes which the guideline committee classed as critical (perinatal death and control of maternal systolic blood pressure). The other outcomes in this table have been classed as important by the guideline committee. The guideline categorised studies on ‘acute’ management as those including care of women with sudden, uncontrolled hypertension, very high blood pressure levels, or with acute symptoms of pre-eclampsia (headache, visual disturbance, upper abdominal pain).
This evidence table is related to the following section/s:
Cochrane Clinical Answers
Cochrane Clinical Answers (CCAs) provide a readable, digestible, clinically focused entry point to rigorous research from Cochrane systematic reviews. They are designed to be actionable and to inform decision making at the point of care and have been added to relevant sections of the main Best Practice text.
- What are the effects of antiplatelet agents for the primary prevention of preeclampsia in at‐risk women?
- How does calcium supplementation commencing before or early in pregnancy compare with placebo for preventing hypertensive disorders in women with a history of pre‐eclampsia?
- How does Doppler ultrasound compare with no ultrasound for improving infant outcomes in high-risk pregnancies?
- How does Doppler ultrasound compare with cardiotocography for improving infant outcomes in high-risk pregnancies?
- How does interventionist care compare with expectant care for women between 24‐ and 34‐weeks’ gestation who have severe pre‐eclampsia?
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