Maternal and perinatal outcomes amongst haemoglobinopathy carriers: a systematic review. 
With the introduction of screening programmes for haemoglobinopathies (HbP), more women will be aware of their HbP status.  The genetic risk for women who are carriers of HbP is well known.  However, midwives and obstetricians need to know whether there are other risks involved in the pregnancies of women who are carriers of HbP. The objective of this study was to investigate the hypothesis that being a carrier of HbP has no consequences for the health of pregnant women and the outcome of their pregnancies.  A systematic search was carried out until August 2008 in the Cochrane Library, Medline, EMBASE and CINAHL databases.  All references were inspected to identify further studies.  The authors of key publications were contacted for any unpublished research.  Selection of studies was made on the basis of the following criteria: Cohort and case-control studies, pregnant women with a singleton pregnancy, exposure: HbAS or thalassaemia minor and the following outcomes: urinary tract infection (UTI), anaemia, (pre-)eclampsia, gestational diabetes, premature labour, low birth weight, intrauterine growth retardation, miscarriage, neonatal death, low Apgar score, neural tube defects.  Quality assessment and data extraction were carried out by two researchers.  A total of 780 subjects were identified of which nine were included in the study.  A protective effect of sickle cell trait was found for premature birth, low Apgar score and perinatal mortality rate.  No significant effect was found for low birth weight, growth retardation, UTI or high blood pressure.  The risk of anaemia and bacteriuria was increased.  In conclusion, the risks amongst pregnant HbP carriers are low.  Midwives and obstetricians need to be aware of the risk of anaemia and UTI.