Eleven RCTs, providing data from 945 patients, were included in the review.
Cervical ripening: for pregnancy terminations in the first trimester, less force was required to dilate the cervix when treated with nitroglycerin in comparison with no treatment (1 trial, n=24). Nitroglycerin was less effective than prostaglandin E2 for labour induction and was associated with more minor side-effects (1 trial, n=110).
Acute tocolysis: nitroglycerin given to arrest pre-term labour was more effective than a placebo (1 trial, n=33), but not more effective when compared with ritodrine (1 trial, n=133) or magnesium sulphate (1 trial, n=30). Headache was more common with nitroglycerin in these trials.
Ease of foetal extraction: nitroglycerin was not better than a placebo for uterine relaxation for foetal extraction at Caesarean section or for external version (1 trial, n=97). Maternal hypotension was more common with nitroglycerin.
Success of external version: nitroglycerin was not statistically significantly better than a placebo in the facilitation of external cephalic version, (1 trial, n=57). Adverse events were not reported.
Embryo transfer: a nitroglycerin spray did not ease embryo transfers in comparison with a placebo (1 trial, n=120). Unspecified adverse events were reported to be more common in the nitroglycerin group.
Development of pre-eclampsia: there were no differences in a small trial (n=40) comparing nitroglycerin and placebo patches that measured gestational age at development of pre-eclampsia, foetal growth restriction or pre-term delivery. When summarising these outcomes, more women receiving nitroglycerin had normal pregnancies, with a hazard reduction of 73%. There were no differences in adverse events.
Primary dysmenorrhoea: the application of nitroglycerin patches decrease pain in women with primary dysmenorrhoea in 2 crossover trials (n1=74, n2=14). The nitroglycerin-treated group reported more headaches.
Quality assessment: 9 of 11 assessed studies had a quality score of at least 3 (maximum 5).