The effect of sperm DNA fragmentation on miscarriage rates: a systematic review and meta-analysis.
OBJECTIVE
Is there an association between high levels of sperm DNA damage and miscarriage?


CONCLUSIONS
Miscarriage rates are positively correlated with sperm DNA damage levels.


BACKGROUND
Most ejaculates contain a subpopulation of sperm with DNA damage, also referred to as DNA fragmentation, in the form of double or single-strand breaks which have been induced in the DNA prior to or following ejaculation. This DNA damage may be particularly elevated in some subfertile men, hence several studies have examined the link between sperm DNA damage levels and conception and miscarriage rates.


METHODS
A systematic review and meta-analysis of studies which examined the effect of sperm DNA damage on miscarriage rates was performed. Searches were conducted on MEDLINE, EMBASE and the Cochrane Library without any language restrictions from database inception to January 2012.


METHODS
We used the terms 'DNA damage' or 'DNA fragmentation' combined with 'miscarriage', 'abortion' or 'pregnancy' to generate a set of relevant citations. Data extraction was performed by two reviewers. Study quality was assessed using the Newcastle-Ottawa Scale. Meta-analysis of relative risks of miscarriage was performed with a random effects model. Subgroup analyses were performed by the type of DNA damage test, whether the sperm examined were prepared or from raw semen and for pregnancies resulting from IVF or ICSI treatment.


RESULTS
We identified 16 cohort studies (2969 couples), 14 of which were prospective. Eight studies used acridine orange-based assays, six the TUNEL assay and two the COMET assay. Meta-analysis showed a significant increase in miscarriage in patients with high DNA damage compared with those with low DNA damage [risk ratio (RR) = 2.16 (1.54, 3.03), P < 0.00001)]. A subgroup analysis showed that the miscarriage association is strongest for the TUNEL assay (RR = 3.94 (2.45, 6.32), P < 0.00001).


CONCLUSIONS
There is some variation in study characteristics, including the use of different assays and different thresholds for DNA damage and the definition of pregnancy loss.


CONCLUSIONS
The use of methods which select sperm without DNA damage for use in assisted conception treatment may reduce the risk of miscarriage. This finding indicates that assays detecting DNA damage could be considered in those suffering from recurrent pregnancy loss. Further research is necessary to study the mechanisms of DNA damage and the potential therapeutic effects of antioxidant therapy.


BACKGROUND
None.
Centre for Human Reproductive Science, Birmingham Women's Hospital, Mindelsohn Drive, Edgbaston, Birmingham B15 2TG, UK. lynne.robinson@blueyonder.co.uk
Lynne
L
Robinson
Ioannis D
ID
Gallos
Sarah J
SJ
Conner
Madhurima
M
Rajkhowa
David
D
Miller
Sheena
S
Lewis
Jackson
J
Kirkman-Brown
Arri
A
Coomarasamy
D000022:Abortion, Spontaneous / Q000453:epidemiology* / Q000235:genetics; D015331:Cohort Studies; D020552:Comet Assay; D053938:DNA Fragmentation; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D020287:In Situ Nick-End Labeling; D008297:Male; D016017:Odds Ratio; D011247:Pregnancy; D018570:Risk Assessment; D020554:Sperm Injections, Intracytoplasmic; D013094:Spermatozoa / Q000502:physiology*; D014481:United States