273. Seminal plasma influences pregnancy outcome through effects on both uterine receptivity and the pre-implantation embryo

Abstract

Optimal uterine receptivity and viability of the preimplantation embryo are key requirements for successful initiation of a pregnancy. The molecular and cellular events activated by insemination are thought to play a role in establishing an environment conducive to positive pregnancy outcomes. Previously, we have employed a blastocyst transfer model to demonstrate that lack of uterine exposure to seminal plasma at the time of conception results in fetal growth restriction and impaired postnatal development of progeny. Here we utilise a 2-cell embryo transfer technique to determine the effects of uterine seminal plasma exposure on embryo development and its subsequent effects on pregnancy outcomes at term in the mouse. Two-cell embryos were collected from donor mice and transferred into the oviduct of day 1 pseudopregnant recipient females primed either by mating with vasectomised (vas) males or vasectomised males from which the seminal vesicle glands, the major source of seminal plasma, had been surgically removed (vas + svx). At day 18 of pregnancy there was no difference in the number of total implantations, however fetal weight was reduced by approximately 5% (P < 0.05). Placental weight at day 18 was significantly increased, resulting in an increase in the fetal weight: placental weight ratio, an indicative measure of placental function. At term, progeny from pregnancies initiated in the absence of semen exhibited a 10% reduction in birth weight and remained smaller through the pre-weaning period. Fetal growth retardation was more severe when embryos were transferred at 2-cell stage than in comparable experiments where blastocysts were transferred after development in a normal donor tract. In combination, these experiments demonstrate that seminal plasma exposure at the time of conception impacts on pregnancy outcome through independent actions on both uterine receptivity and embryo development. These findings are important when considering current practises of assisted reproductive technologies, as well as having implications in pregnancy outcomes in the general population where seminal plasma signalling may be compromised.