Effect of body mass index on pregnancy outcomes in a freeze-all policy: an analysis of 22,043 first autologous frozen-thawed embryo transfer cycles in China

Abstract

Background Abnormal BMI is associated with discouraging IVF outcomes in fresh autologous or oocyte donor cycles, whether or not such a relation also holds true for women undergoing frozen-thawed embryo transfer (FET) remains unknown. In addition, it remains unclear the detrimental effect of abnormal BMI on IVF outcomes occurs at the level of ovary or endometrium. Methods A retrospective study involved 22,043 first FET cycles of all women who had undergone a freeze-all policy during the period from January 2010 to June 2017. To control for the embryo factor, our analysis was restricted to women with high-quality embryo transfer. The main outcome measure was live birth rate per embryo transfer. The secondary endpoints included rates of implantation, clinical pregnancy, multiple pregnancy, and pregnancy loss. Multivariate logistic regression analysis was performed to detect the independent effect of BMI on live birth rate after adjusting for important confounding variables. Results In the crude analysis, reproductive outcomes were similar between underweight women and normal-weight controls whereas all parameter outcomes were significantly worse in patients with obesity. After adjustment for a number of confounding factors, underweight women had a marginally significant decrease in rates of implantation (adjusted odds ratio (aOR) 0.91; 95% CI 0.85–0.96), clinical pregnancy (aOR 0.91; 95% CI 0.83–0.99), and live birth (aOR 0.91; 95% CI 0.83–0.99) as compared to the women with normal weight. Obesity was significantly associated with decreased implantation (aOR 0.80; 95% CI 0.73–0.87), clinical pregnancy (aOR 0.81; 95% CI 0.71–0.91), and live birth rates (aOR 0.70; 95% CI 0.62–0.80). Moreover, the pregnancy loss rate, both in the first (aOR 1.46; 95% CI 1.15–1.87) and in the second trimester (aOR 2.76; 95% CI 1.67–4.58), was significantly higher in the obesity group than that in the reference group. Conclusions Among women undergoing first FET with high-quality embryo transfer, low BMI has limited impact on pregnancy and live birth rates. On the contrary, obesity was associated with worse IVF outcomes. Our findings further highlighted that endometrial receptivity played an important role in the poor reproductive outcomes of women with abnormal weight status. Electronic supplementary material The online version of this article (10.1186/s12916-019-1354-1) contains supplementary material, which is available to authorized users.

Major Factors Affecting the Live Birth Rate After Frozen Embryo Transfer Among Young Women

“…They found no statistically significant differences in the implantation rate or live-birth rate among underweight (<18.5 kg/m 2 ), normal weight (18.5-24.9 kg/m 2 ), overweight (25.0-29.9 kg/m 2 ), and obese (≥30.0 kg/m 2 ) women. In contrast, a retrospective study found that obesity was associated with declines in the clinical pregnancy rate and LBR (18). In our study, the number of patients with a BMI ≥ 30 kg/m 2 was only 14, which was a small number of patients.…”

Frozen embryo transfer at the cleavage stage can be performed within the first menstrual cycle following the freeze-all strategy without adversely affecting the live birth rate

“…The effects of female age, [24–26] D3 embryo transfer, [27] and BMI [28,29] on pregnancy outcomes in patients undergoing in vitro fertilization have been demonstrated in many previous studies. Therefore, it is no longer necessary to explain the influence of the above factors on LBR.…”

<p>Adjuvant Vaginal Use of Sildenafil Citrate in a Hormone Replacement Cycle Improved Live Birth Rates Among 10,069 Women During First Frozen Embryo Transfers</p>

“…Endometrial preparation of HRT was performed as described previously. 27 , 28 In short, oral E2 (ethinyloestradiol 75 µg daily, Shanghai Xinyi Pharma, China; or fematon 4 mg, twice daily, Abbott Healthcare Products B.V.) was commenced on the third day of the menstrual cycle; progesterone exposure was initiated when the endometrial thickness reached ≥7 mm. Embryo transfer was performed 3 days after progesterone administration for day 3 embryos or 5 days later for blastocysts.…”