Reproductive and obstetric outcomes in mildly and significantly underweight women undergoing IVF

Impact of maternal body mass index on pregnancy outcomes following frozen embryo transfer: A systematic review and meta-analysis

OBJECTIVE

There is still a significant gap in understanding how maternal body mass index (BMI) impacts outcomes of pregnancy after frozen embryo transfer (FET). This review aims to evaluate the effects of various BMI categories on clinical pregnancy and live birth rates in women undergoing FET.

METHODS

PubMed, Scopus, Embase, and Web of Science databases were searched for studies, published up to March, 2024, using the keywords "obesity", "overweight", "obese", "maternal body mass index," "pregnancy outcomes," "frozen embryo transfer,". Eligible studies were selected based on predefined inclusion criteria, statistical analysis was performed using a random-effects model, and ther results were presented as odds ratios (OR) with 95% confidence intervals (CI).

RESULTS

A total of 17 studies were included in the meta-analysis. Pooled findings indicate significantly reduced live birth rate in underweight (OR 0.93; 95% CI: 0.89, 0.98) and obese (OR 0.85; 95% CI: 0.77, 0.93) women but not in those who were overweight (OR 0.96; 95% CI: 0.92, 1.00), compared to those with normal BMI. Further, only those women who were underweight (OR 0.91; 95% CI: 0.85, 0.97) had reduced odds of clinical pregnancy rate but not those who were overweight (OR 0.99; 95% CI: 0.94, 1.05) or obese (OR 0.92; 95% CI: 0.82, 1.03).

CONCLUSION

Maternal BMI impacts pregnancy outcomes after frozen embryo transfer, with underweight and obese women having lower live birth rates and only underweight women showing reduced clinical pregnancy rates compared to those with normal BMI. These findings underscore the importance of addressing BMI in women undergoing FET to improve pregnancy outcomes.

Being underweight or obese in adolescence may increase the risk of female infertility later in life: The Japan Nurses' Health Study

OBJECTIVES

Underweight or obesity is associated with infertility in women, but large cohort studies with a life course perspective are rare. We explored the association between body mass index (BMI) at age 18 and subsequent infertility among Japanese women.

STUDY DESIGN

In total, 15,907 married women aged 30-44 years who participated in a prospective cohort baseline survey during 2001-2007 were cross-sectionally analyzed. Those with a history of cancer, and those with a partner with infertility or missing data were excluded. All data were obtained from self-reported questionnaires.

MAIN OUTCOME MEASURES

The main outcome measure was infertility, defined as a self-reported history of infertility for at least 2 years. Age and cause of infertility were also recorded.

RESULTS

Overall, 2825 participants (17.8 %) reported being infertile. The proportions of women who were underweight (BMI <18.5 kg/m2), overweight (BMI ≥25 and < 30 kg/m2), and obese (BMI ≥ 30 kg/m2) at age 18 were 12.8 %, 4.5 %, and 0.4 %, respectively. Multiple logistic regression analysis revealed a 1.31-fold and a 1.82-fold increase in the rate of infertility in those women who were underweight or obese during adolescence, respectively, compared with those of normal weight. Further analysis by cause of infertility revealed no significant associations with overweight or obesity at age 18, but being underweight was positively associated with infertility of unknown cause.

CONCLUSIONS

Being underweight or obese at adolescence is a potential risk factor for subsequent infertility among Japanese women. In particular, being underweight during adolescence may be a contributing factor to unexplained infertility later in life.

Mild obesity does not affect perinatal outcome in gestational carrier cycles

STUDY QUESTION

Does BMI of gestational carriers (GCs) affect perinatal outcomes after embryo transfer?

SUMMARY ANSWER

Overweight and class I obesity in GCs does not affect the rate of good perinatal outcomes.

WHAT IS KNOWN ALREADY

The use of GCs is increasing, but uniform guidance regarding optimal BMI for GCs is lacking. Women with obesity who conceive without fertility treatment or through autologous or donor in vitro fertilization are at higher risk of adverse maternal and fetal outcomes, but data on obesity in GCs are very limited.

STUDY DESIGN, SIZE, DURATION

We performed a retrospective cohort study of 1121 GC cycles from January 2015 to December 2020 at US Fertility, the largest national partnership of fertility practices in the USA.

PARTICIPANTS/MATERIALS, SETTING, AND METHODS

All GC cycles performed at a large network of fertility practices were reviewed. Same-sex partners undergoing co-IVF were excluded. The primary outcome was good perinatal outcome from the first embryo transfer, defined as a singleton live birth at ≥37 weeks of gestation with birth weight between 2500 and 4000 g. Secondary outcome measures included frequencies of live birth, clinical pregnancy, miscarriage, full-term birth, low birth weight, large for gestational age, and cesarean delivery. A generalized linear model (log-binomial) was used for each to compare outcomes across BMI groups using normal BMI (20-24.9 kg/m2) as the reference group. Risk ratios and 95% CIs were estimated for each category group relative to normal BMI.

MAIN RESULTS AND THE ROLE OF CHANCE

We identified 1121 cycles in which GCs underwent first embryo transfer, of which 263 (23.5%) were in GCs with BMI >30. Demographics and reproductive history for GCs did not differ by BMI groups. The age of intended parents, use of frozen eggs, and fresh embryo transfers were higher with increasing BMI group. There were no statistically significant associations between BMI and good perinatal outcomes, live birth, clinical pregnancy, biochemical, spontaneous abortion, or low birth weight. However, among live births, higher BMI was significantly associated with birth by cesarean (P = 0.015) and large for gestational age infants (P = 0.023).

LIMITATIONS, REASONS FOR CAUTION

This was a retrospective study, and there may be unmeasured confounders. The number of patients with BMI <20 or ≥35 was small, limiting the power for these groups. We were not able to assess all maternal and fetal outcomes.

WIDER IMPLICATIONS OF THE FINDINGS

In this study, we did not identify any significant impact of BMI on the chances of having a good perinatal outcome. Prior research studies have been inconsistent and this is the largest study to date.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was received for this work. The authors do not have any conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Endometrium development patterns and BMI groups among in vitro fertilization patients; prognostic aspects

Introduction

The impact of the obesity pandemic on female reproductive capability is a factor that needs to be investigated. In addition, the link between endometrial thickness and in vitro fertilization (IVF) outcomes is contentious.

Goal

Our goal was to analyze the association among endometrium development, hormone levels, embryo quality, clinical pregnancy, anamnestic parameters, and body mass index (BMI) in women receiving IVF treatment.

Patients and methods

537 participants undergoing IVF/ICSI cycles with successful oocyte retrieval were enrolled. Subjects were divided into four BMI based groups: underweight (UW; n=32), normal weight (NW; n=324), overweight (OW; n= 115), obesity (OB; n=66). Anthropometric and anamnestic parameters, characteristics of stimulation, endometrial thickness on the day of hCG injection, at puncture, at embryo transfer, FSH, LH, AMH, partner's age and the semen analysis indicators, embryo quality, clinical pregnancy, were recorded and analyzed. Support Vector Machine (SVM) was built to predict potential pregnancies based on medical data using 22 dimensions.

Results

In accordance with BMI categories, when examining pregnant/non-pregnant division, the average age of pregnant women was significantly lower in the UW (30.9 ± 4.48 vs. 35.3 ± 5.49 years, p=0.022), NW (34.2 ± 4.25 vs. 36.3 ± 4.84 years, p<0.001), and OW (33.8 ± 4.89 vs. 36.3 ± 5.31 years, p=0.009) groups. Considering FSH, LH, and AMH levels in each BMI category, a statistically significant difference was observed only in the NW category FSH was significantly lower (7.8 ± 2.99 vs. 8.6 ± 3.50 IU/L, p=0.032) and AMH (2.87 ± 2.40 vs. 2.28 ± 2.01 pmol/L, p=0.021) was higher in pregnant women. There were no further statistically significant differences observed between the pregnant and non-pregnant groups across any BMI categories, especially concerning endometrial development. Surprisingly, BMI and weight correlated negatively with FSH (r=-0.252, p<0.001; r=-0.206, p<0.001, respectively) and LH (r= -0.213, p<0.001; r= -0.195, p<0.001) in the whole population. SVM model average accuracy on predictions was 61.71%.

Discussion

A convincing correlation between endometrial thickness development and patients' BMI could not be substantiated. However, FSH and LH levels exhibited a surprising decreasing trend with increasing BMI, supporting the evolutionary selective role of nutritional status. Our SVM model outperforms previous models; however, to confidently predict the outcome of embryo transfer, further optimization is necessary.

Higher live birth rates are associated with a normal body mass index in preimplantation genetic testing for aneuploidy frozen embryo transfer cycles: a Society for Assisted Reproductive Technology Clinic Outcome Reporting System study

OBJECTIVE

To determine whether body mass index (BMI) was associated with live birth in patients undergoing transfer of frozen-thawed preimplantation genetic testing for aneuploidy (PGT-A) embryos.

DESIGN

Retrospective cohort study of cycles reported to the Society for Assisted Reproductive Technology Clinic Outcome Reporting System.

SUBJECTS

All autologous and donor recipient PGT-A-tested cycles reported to the Society for Assisted Reproductive Technology Clinic Outcome Reporting System from 2014 to 2017.

INTERVENTION(S)

Body mass index.

MAIN OUTCOME MEASURE(S)

The primary outcome measure was the live birth rate, and the secondary outcome measures were the clinical pregnancy and biochemical pregnancy rates. Multivariable generalized additive mixed models and log-binomial models were used to model the relationship between BMI and outcome measures.

RESULT(S)

A total of 77,018 PGT-A cycles from 55,888 patients were analyzed. Of these cycles, 70,752 were autologous, and 6,266 were donor recipient. In autologous cycles, a statistically significant and clear nonlinear relationship was observed between the BMI and live birth rates, with the highest birth rates observed for the BMI range of 23-24.99 kg/m2. When using 23-24.99 kg/m2 as the referent, other BMI ranges demonstrated a lower probability of live birth and clinical pregnancy that continued to decrease as the BMI moved further from the reference value. Patients with a BMI of <18.5 kg/m2 had a 11% lower probability of live birth, whereas those with a BMI of ≥40 kg/m2 had a 27% lower probability than the referent.

CONCLUSION(S)

A normal-weight BMI range of 23-24.99 kg/m2 was associated with the highest probability of clinical pregnancy and live birth after a frozen-thawed PGT-A-tested blastocyst transfer in both autologous and donor recipient cycles. A BMI outside the range of 23-24.99 kg/m2 is likely associated with a malfunction in the implantation process, which is presumed to be related to a uterine factor and not an oocyte factor, as both autologous and donor recipient cycle outcomes were associated similarly with the BMI of the intended parent.

Body mass index impacts ectopic pregnancy during in vitro fertilization: an analysis of 42,362 clinical pregnancy cycles

PURPOSE

This large, single-center, retrospective cohort study was aimed to explore the effect of female body mass index (BMI) on ectopic pregnancy (EP) following fresh and frozen-thawed embryo transfers (ET).

METHODS

A total of 27,600 pregnancies after fresh ET and 14,762 pregnancies after frozen-thawed ET were included between January 2010 to June 2022. Women were divided into three groups based on BMI according to the Working Group on Obesity in China (WGOC), International Life Sciences Institute (ILSI): underweight (BMI < 18.5 kg/m2), normal weight (BMI, 18.5-23.9 kg/m2), and overweight or obesity (≥ 24 kg/m2). Compare EP rates among BMI categories in fresh and frozen-thawed ET cycles respectively. Multivariate logistic regression analyses were used to investigate the association between female BMI and EP.

RESULTS

The overall EP rates in fresh, and frozen thawed transfer cycles were 2.43% (672/27,600) and 2.82% (417/14,762), respectively. In fresh ET cycles, underweight women yielded a significantly higher EP rate than those with normal and excess weight (3.29% vs. 2.29% vs. 2.54%, P = 0.029). But EP rates did not differ among the three BMI groups (2.72% vs. 2.76% vs. 2.96%, P = 0.782) in frozen-thawed ET cycles. In fresh ET cycles, after adjusting for potential confounding factors, no significant association was found between female BMI and EP occurrence (adjusted OR: 0.98, 95% CI 0.70-1.37, P = 0.894, for BMI 18.5-23.9 kg/m2; adjusted OR: 0.89, 95% CI 0.75-1.06, P = 0.205, for BMI ≥ 24 kg/m2. Reference = BMI < 18.5 kg/m2).

CONCLUSION(S)

Female BMI did not affect the occurrence of ectopic pregnancy in either fresh or frozen-thawed embryo transfer cycles.

Effects of body mass index on IVF outcomes in different age groups

BACKGROUND

Herein, we aimed to analyse the effects of body mass index (BMI) on the treatment outcomes of in vitro fertilisation (IVF) in a cohort of women undergoing their first IVF cycle.

METHODS

A total of 2311 cycles from 986 women undergoing their first IVF/intracytoplasmic sperm injection cycle with fresh/frozen embryo transfer between January 2018 and December 2021 at the Center of Reproductive Medicine, Shuguang Hospital affiliated to Shanghai University of Traditional Chinese Medicine, were considered in this retrospective cohort study. First, the included patients were classified into four groups based on their BMI: underweight (BMI < 18.5 kg/m2, 78 patients), normal weight (18.5 ≤ BMI < 24 kg/m2, 721patients), overweight (24 ≤ BMI < 28 kg/m2, 147 patients), and obese (BMI ≥ 28 kg/m2, 40 patients). The IVF outcomes included the Gn medication days; Gn dosage; number of retrieved oocytes, mature oocytes, fertilized oocytes, cleavages, and available embryos and high-quality embryos; implantation rate; clinical pregnancy rate and live birth rate. Next, all the obtained data were segregated into three different subgroups according to the patient age: < 30 years, 30-38 years and > 38 years; the IVF pregnancy outcomes were compared among the groups.

RESULTS

Compared with the other three groups, the underweight group had a higher number of fertilized oocytes, cleavage and available embryos and a smaller Gn medication days and required a lower Gn dosage. There was no difference in the number of retrieved oocytes and mature oocytes among the groups. Moreover, compared with the women aged 30-38 years in the overweight group, those in the normal weight group had a significantly higher implantation rate, clinical pregnancy rate and live birth rate (p = 0.013 OR 1.75, p = 0.033 OR 1.735, p = 0.020 OR 1.252 respectively). The clinical pregnancy rate was also significantly higher in those aged 30-38 years in the normal weight group than in the obese group (p = 0.036 OR 4.236).

CONCLUSIONS

Although the BMI can greatly affect the pregnancy outcomes of women aged 30-38 years, it has almost no effects on the outcomes of younger or older women.

Is telephone follow-up reliable in maternal and neonatal outcomes surveys in in vitro fertilization?

BACKGROUND

 Many studies that collect maternal and neonatal outcomes rely on patient self-report phone calls. It is unclear how reliable or accurate these phone call reports are.

OBJECTIVE

To evaluate the reliability of telephone calls in information collection in IVF.

STUDY DESIGN

The women were interviewed seven days after delivery by a nurse via telephone. The maternal and neonatal outcomes were recorded based on a self-report from one of the spouses. Meanwhile, the standardized electronic hospitalized discharge records were extracted from the hospital medical database. For each case, maternal and neonatal information obtained from telephone interviews and extracted from medical files were compared.

RESULTS

Agreement was classified as "almost perfect, K = 0.81-1.00" for preterm birth, cesarean delivery, low birth weight baby, and macrosomia. The strength of agreement was classified as "moderate, K = 0.41-0.60" for some antepartum complications: gestational diabetes (K = 0.569); pregnancy-induced hypertension (K = 0.588); intrahepatic cholestasis of pregnancy (K = 0.597) and oligohydramnios (K = 0.432). The strength of agreement between telephone interviews and hospitalized discharge records can be classified as "slight (K = 0-0.20)" for some complications: thyroid diseases (K = 0.137), anemia (K = 0.047), postpartum hemorrhage (K = 0.016), and Fetal distress (K = 0.106).

CONCLUSION

Some variables (preterm birth, cesarean delivery, birth weight) information collected by telephone follow-up were reliable. However, other complications (thyroid diseases, anemia, postpartum hemorrhage, and fetal distress) collected via self-report was non-reliable. Compared with complications during labor, antepartum complications have higher agreement between different follow-up methods. IVF records and hospitalized discharge records should be matched and collected simultaneously when discussing maternal and neonatal outcomes of IVF.

Maternal underweight does not adversely affect the outcomes of IVF/ICSI and frozen embryo transfer cycles or early embryo development

OBJECTIVE

To compare assisted reproductive technology (ART) outcomes and preimplantation embryo development between underweight and normal-weight women.

METHODS

This retrospective cohort study included 26 underweight women (body mass index [BMI] < 18.50 kg/m²) and 104 normal-weight women (BMI >20 and <24.9 kg/m²) who underwent a total of 204 in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles and 358 fresh/frozen embryo transfers (ET) in our institution between January 2016 and December 2018. Statistical analyses compared selected ART outcomes (ovarian stimulation, fertilization, and pregnancy) between both weight groups. Morphokinetic and morphological parameters were also compared between 346 and 1467 embryos of underweight and normal-weight women, respectively.

RESULTS

The mean ± standard deviation age of the underweight and normal-weight women was similar (31.6 ± 4.17 vs 32.4 ± 3.59 years; p = .323). There were no differences in the peak estradiol levels, the number of retrieved oocytes, the number of metaphase II oocytes, and the oocyte maturity rates between the two groups. The IVF/ICSI fertilization rates and the number of embryos suitable for transfer or cryopreservation were similar for both groups. All morphokinetic parameters that were evaluated by means of time-lapse imaging as well as the morphological characteristics were comparable between low and normal BMI categories. There were no significant differences in pregnancy achievement, clinical pregnancy, live births, and miscarriage rates between the suboptimal and optimal weight women.

CONCLUSION

Underweight status has no adverse impacts on the outcomes of IVF/ICSI with either fresh or frozen ET or on preimplantation embryo development and quality.