The effect of smoking on oocyte quality and hormonal parameters of patients undergoing in vitro fertilization-embryo transfer

Abstract

Purpose: The aim of the present study was to investigate the influence of smoking on different parameters such as oocyte count, embryo score, and basal hormone values within the scope of in vitro fertilization-embryo transfer (IVF-ET).

Methods: Eight hundred thirty-four women undergoing IVF-ET treatment were classified as smokers or nonsmokers on the basis of questionnaires. Additionally, we divided them into three groups according to their stimulation protocol--"combined stimulation" [I; clomiphene citrate plus human menopausal gonadotropin (hMG)], "ultrashort" [II; gonadotropin releasing hormone agonist (GnRHa) plus hMG or follicle-stimulating hormone (FSH)], and "long downregulation protocol" (III)--and further classified again as smokers or nonsmokers within the groups.

Results: In general, smoking patients were significantly (P = 0.0195) younger than nonsmokers and showed a significantly (P = 0.0379) lower embryo score and a tendency (P = 0.0931) to produce fewer oocytes. There was no significant difference concerning the number of normally or pathologically fertilized and transferred oocytes and embryos suitable for cryopreservation. Women who smoked had significantly (P = 0.0112) higher basal 17-beta-estradiol (E2), luteinizing hormone (LH) (P = 0.0001), and dehydroepian-drosteronesulfate (DHEAS) (P = 0.0039) levels, but their basal human prolactin (HPRL) levels were significantly (P = 0.0033) lower than those of nonsmokers. According to the stimulation protocol used, we found the following results. Smoking patients in group I showed a significantly (P = 0.023) lower embryo score and produced fewer oocytes (P = 0.0113), with fewer of them being fertilized (P = 0.0072) and transferred (P = 0.0067). Women who smoked had significantly (P = 0.0002) higher basal LH levels, but their HPRL levels were significantly (P = 0.031) lower than those of nonsmokers. Furthermore, they had a thinner endometrium on the day of embryo transfer (P = 0.0366). In group II we measured significantly elevated basal E2 levels (P = 0.0089) and higher LH values (P = 0.0092) in smokers. Group III showed a trend (P = 0.0565) toward lower HPRL values in smokers.

Conclusions: Although the fertilization rate of oocytes and the pregnancy rate were not significantly different between smokers and nonsmokers, we found significantly alterated hormonal parameters and negatively influenced oocyte parameters, particularly after clomiphene stimulation. So we might consider using only GnRHa protocols for smoking patients. Additionally, we advise our patients to stop smoking before an IVF-ET treatment because of the complex effects of smoking on the reproductive and hormonal system.