CRD summary

This review concluded that histamine 2 blockers can be used safely in pregnancy. These conclusions were supported by the results presented, but should be interpreted with caution as very few details were provided on the participants in the included studies and on methodological quality.

Authors' objectives

To evaluate the safety of histamine 2 (H2) blockers in pregnancy.

Searching

MEDLINE, EMBASE, International Pharmaceutical Abstracts, EBM Reviews and CINAHL were searched from inception to January 2008 using reported search terms. References from retrieved studies and reviews were screened. No language restrictions were applied.

Study selection

Studies that compared women in at least the first trimester of pregnancy who had and had not been exposed to H2 blockers and that reported details on congenital malformations were eligible for inclusion. Outcomes assessed in the review were congenital malformations, spontaneous abortions, premature delivery and birth weight.

Two reviewers independently assessed studies for inclusion; disagreements were resolved through consensus.

Assessment of study quality

Studies were assessed for methodological quality according to the Downs-Black scale to assess studies for quality of reporting, external and internal validity, bias, confounding and power, and assign a score out of a maximum of 32.

The authors did not state how many reviewers performed the validity assessment.

Data extraction

Data were extracted on number of women in exposed and unexposed groups with each of the outcomes of interest.

The authors did not state how many reviewers performed the data extraction.

Methods of synthesis

Summary odds ratios (OR) and 95% confidence intervals (CI) were estimated using random-effects models. Heterogeneity was assessed using the Q statistic. Publication bias was assessed using funnel plots.

Results of the review

Four studies (n=122,290) were included: two prospective cohorts (n=2,228) and two retrospective cohorts (n=120,062). Average quality score was 70%, which suggested fair to good quality.

There was no significant difference in the incidence of congenital malformations (four studies), spontaneous abortion (three studies), preterm delivery (four studies) and small for gestational age (two studies) in women exposed to H2 blockers in pregnancy compared to those not exposed. There was no evidence of heterogeneity between studies (p=0.33).

There was no evidence of publication bias.

Authors' conclusions

H2 blockers can be used safely in pregnancy.

CRD commentary

The review addressed a focused question supported by clearly defined inclusion criteria. The search was appropriate for published studies. No specific attempts were made to locate unpublished studies, which raised the possibility of publication bias; this was assessed in the review. Appropriate steps were taken to minimise bias and errors in the selection of studies; it was unclear whether such steps were taken for quality assessment and data extraction. Study quality was assessed using appropriate criteria, but the results of this were presented only as a median summary quality score across studies; therefore, it was unclear whether study quality varied across studies and which particular methodological features were potential sources of bias in the included studies. Details on the women included in the studies and the settings in which they were conducted were lacking, so it was not possible to determine the generalisability of results. Methods of analysis were appropriate and the authors' conclusions were supported by the results presented. However, the conclusions should be interpreted with caution due to the lack of details regarding the included studies.

Implications of the review for practice and research

Practice: The authors stated that H2 blockers can be considered safe in managing heartburn and acid reflux in pregnancy.

Research: The authors did not state any implications for research.

Funding

Duchesnay, Inc, Canada.

Bibliographic details

Gill SK, O'Brien L, Koren G. The safety of histamine 2 (H2) blockers in pregnancy: a meta-analysis Digestive Diseases and Sciences 2009; 54(9): 1835-1838. [PubMed: 19051023]

Original Paper URL

http://www.springerlink.com/content/j682787vr16h1546/

Indexing Status

Subject indexing assigned by NLM

MeSH

Female; Fetus /drug effects; Heartburn /drug therapy; Histamine H2 Antagonists /adverse effects; Humans; Pregnancy; Pregnancy Complications /drug therapy

AccessionNumber

12009107438

Database entry date

24/03/2010

Record Status

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.