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expert reaction to study looking at health of dads-to-be before conception and pregnancy outcomes including miscarriage and stillbirth

A study published in Human Reproduction looks at whether preconception paternal health is associated with pregnancy loss in the U.S.


Dr Channa Jayasena is a Reader & Consultant in Reproductive Endocrinology, Imperial College London, said:

“It has long been established that healthy mums have the best chance of making healthy babies; this report highlights the critical importance of having healthy dads, too.  They have studied health data from nearly a million pregnancies in the US, observing that less healthy men have higher risks of pregnancy loss.  These findings support several recent studies suggesting that poor metabolic health such as obesity reduce sperm quality.  The message is that men need to get into shape to maximise their chances of becoming a dad.”


Prof Sheena Lewis, Honorary Professor, Queen’s University Belfast, said:

“This is a large well-designed study.  It shows clearly that poor health in men preparing to be dads is linked to their partners having miscarriages.  This is a vital public health message for men prior to fatherhood.  They must optimise their health before conception to increase their chances for having a healthy baby.  It is also a clear message to those of us working in  the fertility sector to make male health a priority and support men in making healthy lifestyle choices.  Further studies are needed to determine what poor male health does to a man’s sperm health.”


Mark Wilcox DM FRCOG, Group Medical Director of CARE Fertility, said:

“This is a very interesting study which adds significantly our growing knowledge of the impact of sperm quality (and not just numbers) on pregnancy outcome.  Indeed, this retrospective, observational study helps us to quantify those effects analysed, such as weight and smoking.  It might have been helpful to recognise and discuss other related male factors, such as oxidative stress and genes (e.g. Annexin A5 M2 haplotype) that are known to affect pregnancy outcomes.”


Prof Allan Pacey, Professor of Andrology, University of Sheffield, said:

“We have suspected for some time that the risk of miscarriage in a woman might be influenced by the health or biology of her partner, such as his age or the quality of the sperm he produces.  As such, this is an interesting study, from a well established group, that takes the concept one step further.  It shows an interesting association between measurable health conditions of the father, such as diabetes or high blood pressure, and the subsequent risk of any miscarriage in his partner.  The results are interesting, and they will help to focus future studies more precisely.  However, it is important to note that the authors have described an association and not a direct cause and effect.  For anyone considering pregnancy in the near future, the study does reinforce the notion that both partners should try and be as healthy as possible.  If either partner is concerned about aspects of their health prior to trying for a pregnancy, they should consult their family doctor.”


Prof Richard Anderson, Elsie Inglis Professor of Clinical Reproductive Sciences, Head of Section of Obstetrics and Gynaecology, and Deputy Co-Director of the MRC Centre for Reproductive Health, University of Edinburgh, said:

“This very large analysis suggests that less healthy men produce poorer quality sperm and that has an important influence of the outcome of a pregnancy.  It was able to take into account aspects of the health of the woman, and indicates that on top of that, her man’s health influenced the risk of miscarriage and stillbirth, although from this type of analysis it’s not possible to be certain of the effect.  We need wider recognition that men’s health is important in achieving healthy babies, and studies to test how that can best be achieved.”


Prof Andrew Prentice FMedSci, Head of Nutrition Theme, MRC Unit The Gambia at London School of Hygiene & Tropical Medicine, said:

“This is an impressive analysis based on a very large sample size and with careful adjustments for confounders.  It shows a clear link between a father’s metabolic health prior to the conception of the baby and the chances that the pregnancy will produce a healthy baby.

“The study is observational so cannot prove cause and effect.  However, we could not reasonably confer any reverse causality (i.e. pregnancy losses causing father-to-be’s metabolically unfit months previously) so the only issue surrounds confounding.  The analysis nicely adjusts for age of both parents and metabolic ill health in the mum so seems pretty robust to me.

“If it is casual, the mechanisms are currently unknown but there are many plausible pathways by which the father’s sperm can be altered as it matures.  These include epigenetic changes in the sperm DNA and changes in small RNA molecules within the sperm.  For couples planning a pregnancy, maintaining a healthy weight and varied diet, quitting smoking and moderating alcohol intake, are probably just as important for fathers as for mothers.”



‘Association between preconception paternal health and pregnancy loss in the USA: an analysis of US claims data’ by Alex M. Kasman et al. was published in Human Reproduction at 00:05 UK time on Friday 18 December 2020.

DOI: 10.1093/humrep/deaa332



Declared interests

Dr Channa Jayasena: “No conflicts of interest.  CNJ holds an NIHR Fellowship investigating the effects of obesity on male fertility.”

Prof Sheena Lewis: “SEM Lewis is CEO of Examenlab Ltd, a university molecular diagnostics company specialising in male reproductive health.”

Prof Allan Pacey: “Chairman of the advisory committee of the UK National External Quality Assurance Schemes in Andrology, Editor in Chief of Human Fertility and Trustee of the Progress Educational Trust (all unpaid).  Also, recent work for the World Health Organisation, British Broadcasting Corporation, Purple Orchid Pharma (paid consultancy with all monies going to University of Sheffield).  Co-applicant on a research grant from the Medical Research Council (ref: MR/M010473/1).”

Prof Richard Anderson: “I don’t have any relevant COIs.”

Prof Andrew Prentice: “I have no conflicts to declare.”

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