The effects of maternal/paternal obesity on gamete health/fertility is well defined, however combined effects of both parents being overweight/obese on embryo development and pregnancy outcome has received limited attention. The aims of this study were to determine the combined effect of paternal and maternal obesity on fertilisation, blastocyst development and pregnancy using established mouse models of paternal/maternal obesity.
Male and female mice were fed a control diet (CD, 6% fat) or a high fat diet (HFD, 21% fat) for 9 and 6 weeks respectively to induce obesity. Animals were mated in a 2x2 study design 1) CD fed parents 2) CD mother, HFD father, 3) HFD mother, CD father, or 4) HFD fed parents. Sperm binding, fertilisation rates and subsequent blastocyst development and cell numbers were determined (n=150). In addition blastocysts were transferred (n=60) into pseudo-pregnant mothers for assessment of implantation and fetal development.
Paternal obesity reduced sperm binding and fertilization rates (-80%, p<0.05) independent of maternal obesity. Paternal obesity, irrespective of maternal obesity, reduced on time embryo development (-20%, p<0.05), while maternal obesity had minimal effect. Blastocyst total cell number and inner cell mass number were only reduced by combined paternal and maternal obesity (-6%, p<0.05), while epiblast cell number were reduced by paternal obesity irrespective of maternal obesity (-62%, p<0.05). Paternal obesity alone reduced embryo implantation rates (-19%, p<0.05) and placental weights (-25%, p<0.05), while increasing fetal weights (15%, p<0.05). Maternal obesity alone had not effect on fetal weights however increased placental weights (23%, p<0.05). Combined maternal and paternal obesity further reduced both fetal (11%, p<0.05) and placental weights (-14%, p<0.05).
This study suggests that blastocyst health and development are more dependent on paternal obesity. Additionally paternal and maternal obesity act additively to impair fetal and placental development implicating the need for a combined approach of peri-conception lifestyle counselling.