BMI and miscarriage after IVF

Abstract

Purpose of reviewTo summarize recent findings related to the risk of miscarriage in women with elevated BMI undergoing IVF, and the mechanisms involved in said risk.Recent findingsMiscarriage rates are increased in overweight and obese women in both natural and assisted reproduction. Oocyte and embryo quality assessed according to classic morphological static parameters does not seem to be affected by excessive female body weight. Despite the initial lack of consensus between studies regarding embryo morphokinetics in obese women, blastocyst formation and quality have recently been shown to be similar across BMI groups, even in the case of euploid embryos. However, some metabolomic differences have been described in oocytes and embryos from obese women, thus pointing to a functional alteration. In women with elevated BMI, the percentage of aneuploid embryos is similar to that of normal weight women, and rates of miscarriage are higher, despite the transfer of euploid embryos. Therefore, the origin of the increased pregnancy loss rate after IVF in these women may be related to metabolomic, epigenetic or mitochondrial oocyte and embryo disturbances, or to the abnormal endocrine, metabolic and inflammatory uterine environment induced by obesity, which seems to be also responsible for other numerous complications during pregnancy and the in-utero fetal programming of postnatal diseases. A displacement of the window of implantation in obese women undergoing artificial endometrial preparation has recently been described and may be related to the poorer embryo implantation rates and increased risk of miscarriage observed following fresh and frozen embryo transfers with autologous oocytes, and with donated ova in recipients with extremely high BMI.SummaryFemale obesity is related to poorer outcome in natural and assisted conception, including an increased risk of miscarriage. Embryo morphology, assessed by conventional methods or by morphokinetics, does not seem to be affected by excess weight, with similar blastocyst formation and quality than normal weight women reported in IVF cycles. Embryo aneuploidy is not increased, and higher miscarriages rates are seen after euploid embryo transfer in obese women. Disturbances of the uterus or its environment induced by female obesity seem to be the most likely cause of the increased risk of miscarriage, although metabolomic, epigenetic or mitochondrial oocyte and embryo dysfunction cannot be ruled out as cannot congenital anomalies. In the context of all the above, weight reduction before pregnancy should be advised in obese women trying to become pregnant.

Smaller than expected crown-rump length ultrasound measurements in 1st-trimester pregnancy: does it have any risk of subsequent pregnancies?

“…15,16 Literature suggests that whether they used assisted reproductive techniques or natural conception, overweight or obese women are at a considerably higher risk of miscarriage. [17][18][19][20][21] CRL is a significant indicator of early fetal growth and neonatal outcome. Thelatest study has reported various maternal characteristics such as maternal age, parity, BMI, and folic acid supplementation as independently associated factors of CRL in the first trimester.…”

Update on obesity and assisted reproductive technology

“…In both natural and ART, MR is risen in overweight and obese women [6]. The performance of oocytes and embryos as measured by classic morphometric static variables does not appear to be influenced by inordinate female body weight.…”

“…women have the same embryo morphokinetic progression, blastocyst forming incidence, and blastocyst morphological characteristics [6]. On the contrary side, García-Ferreyra et al revealed that a higher BMI impacts cell growth and decreases childbirth, implantation rate, and LBR [7].…”

Local glucose elevation activates pyroptosis via NLRP3 inflammasome in ovarian granulosa cells of overweight patients

“…Among this vast population, 40% of women at reproductive age are prone to infertility or subfertility 2 . Although in vitro fertilization (IVF) is an effective treatment for infertility, OW is associated with an increased rate of fetal loss or miscarriage 3–5 . It has been suggested that OW has a detrimental effect on ovarian responsiveness and oocyte quality, 6 however, more evidence is needed to elucidate the mechanism.…”

“…2 Although in vitro fertilization (IVF) is an effective treatment for infertility, OW is associated with an increased rate of fetal loss or miscarriage. [3][4][5] It has been suggested that OW has a detrimental effect on ovarian responsiveness and oocyte quality, 6 however, more evidence is needed to elucidate the mechanism. Accumulating evidence indicates that granulosa cells (GCs), which play fundamental roles in follicular development, are susceptive to the altered follicular microenvironment in OW women.…”