Infertility has become more common, with an increased exposure to toxic compounds including heavy metals (HM). Follicular fluid (FF) surrounds the developing oocyte in the ovary and can be analysed to assess metal content. The levels of twenty-two metals were measured in the FF of ninety-three females in a reproduction unit, and their influence on assisted reproduction technique (ART), were examined. The metals were determined by optical emission spectrophotometry. Low values of copper, zinc, aluminium, and calcium favour polycystic ovary syndrome. The relationships between the number of oocytes and metals: iron (rs=0.303; p=0.003) and calcium (rs=−0.276; p=0.007) are significant, as well as between the number of mature oocytes with iron (rs=0.319; p=0.002), calcium (rs=−0.307; p=0.003) and sodium (rs=−0.215; p=0.039) and are near to significance in the case of aluminium (rs=−0.198; p=0.057). In the group with a fertilisation rate ≤ 75%, 36% of the women presented calcium >176.62 mg/kg compared to the group with a fertilisation rate ≥ 75% where this percentage was only 10% (p=0.011). An excess of iron and calcium reduces the good quality embryo rate, and an excess of potassium impairs the blastocyst rate. If potassium is above 237.18 mg/kg and calcium is below 147.32 mg/kg, these conditions favour embryo implantation. Pregnancy is influenced by high potassium and low copper levels. Controlling exposure to toxic elements is recommended for all couples with reduced fertility or receiving an ART.

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Increased levels of metal ions in human seminal fluid have a significant correlation with male fertility. Few publications explain the effect of metals in semen and their influence on assisted reproductive treatments. Semen parameters and the levels of twenty-two metals were measured in the seminal fluid of 102 men attended in a Reproductive Unit. Metals were determined by optical emission spectrophotometry. A statistical relationship was found between spermiogram and iron, which was lower than expected in pathological spermiograms (p = 0.032); zinc (p = 0.066), calcium (p = 0.047), and magnesium (p = 0.048) mean levels were higher in normozoospermics. More days of sexual abstinence correlates with higher seminal zinc (p = 0.001) and magnesium levels (p = 0.002). Lower vanadium values were found to be associated with higher fertilization rates (p = 0.039). Higher values of lead (p = 0.052) and vanadium (p = 0.032) were obtained in patients who did not reach 100% embryo cleavage rate. Aluminium (p = 0.042) and sodium (p = 0.002) were found in lower amounts associated with better blastocyst rates. The implantation rate shows an inverse association with women’s age and iron and calcium content, compared to magnesium and sodium which presented a significant direct association with this percentage. A significant direct relationship was found between the positive evolution of pregnancy and the values of zinc (p = 0.004), calcium (p = 0.013), potassium (p = 0.002), and magnesium (p = 0.009). The study confirms that zinc, iron, calcium, sodium, aluminium, magnesium, vanadium, and lead have positive–negative effects on reproduction and support the analysis of metals in semen as a new line of study on male fertility with implications for reproductive outcomes.