Impact of Body Mass Index (BMI) on Retrieval of Oocyte Numbers in *In Vitro* Fertilization Women

*Linda Wu and Bin Wu*

### **Abstract**

Previous research and clinical reports have discovered that body weight significantly affects a patient's fertility status. Underweight, overweight, or obese women may experience reduced fertility. Currently, assisted reproductive technology (ART) is used as treatment for infertile couples to conceive a child. However, whether abnormal body mass indexes (BMIs) affect infertile oocyte production is not clear. The objective of this study is to determine the association between BMI and retrieved oocyte numbers. A total of 136 IVF patient data in 2016 was reported from Reproductive Health Center. The relationship between patient's BMI and retrieved oocyte numbers has been analyzed and their correlation coefficients between patients' age, oocyte numbers, and BMI have been calculated. The results further proved that BMI affects collecting oocyte numbers and oocyte maturation rate. Overweight patients had fewer oocytes retrieved than that of normal weight patients. Likewise, obese patients had even fewer oocytes retrieved than that of both normalweight and overweight patients. Underweight BMIs seem to have no effect on the number of oocytes collected; however, the oocyte quality and embryo production needs to be further studied. Results from this study may be used by IVF physicians and practitioners when consulting patients for IVF treatments.

**Keywords:** assisted reproductive technology, body mass index, overweight, obese, oocyte number

### **1. Introduction**

The impact of infertility causes significant mental and physical strain on both men and women. Numerous factors can influence male and female fertility. Common causes of female infertility may include anovulation, hormonal imbalances, structural issues or damage to fallopian tubes or uterus, cervical issues, decreased ovarian reserve with increased age, etc. In the past few decades, one rising factor affecting the fertility status is an individual's body weight. Being severely underweight or overweight can disrupt the process of regular, consistent ovulation in females, leading to anovulation. In 2013, the American Society of Reproductive Medicine (ASRM) released "Optimizing Natural Fertility: A Committee Opinion" in which the society

included recommendations on how to counsel patients to optimize the likelihood of becoming pregnant. ASRM reported that fertility rates are decreased in women who are underweight or obese based on body mass index (BMI).

According to the National Heart, Lung, and Blood Institute (NIH), the body mass index (BMI) is a standardized measure of an individual's body fat percentage relative to their height and weight. A normal range is considered to be anywhere between 18.4 and 24.9, whereas an underweight value is below 18.4. Overweight values range from 25 to 29.9. Obese individuals have BMIs of 30 or greater. BMI can be calculated by an individual's weight divided by their height squared (kg/m2 ). In relation to fertility, Hassan and Killick [1] reported that the time to conception was increased by more than twofold among overweight/obese women (BMI >25 kg/m2 ) and by more than fourfold among underweight women (BMI <19 kg/m2 ). With additional research suggesting the impact body weight has on one's fertility status, the ASRM highlighted several points suggesting women who are obese to receive counseling prior to attempting to conceive in order to prevent potential medical, obstetric, or neonatal complications. In addition, the ASRM indicated that diet and exercise are the firstline treatments for obesity, where weight loss is linked to return of ovulation and decreased miscarriage rates in obese women who were previously infertile. Through pharmacotherapy, such as antiobesity medications, including orlistat, lorcaserin, naltrexone, may be used for obese women, it should only be considered for those who do not respond to a 6-month lifestyle modification. Furthermore, bariatric surgery may be considered to improve obesity-related issues regarding menstrual irregularity and infertility in women, however, pregnancy should not be considered within a year after surgery.

Based on the ASRM's guidelines stated above, it is highly recommended for individuals who are severely underweight or overweight/obese to normalize their weight in order to improve their fertility status. Practitioners may provide patients with appropriate recommendations for weight loss/gain programs, nutritional counseling, dietary modifications, and/or exercise regimens. The goal of physicians should be to allow patients to be in their best possible health condition prior to starting any fertility treatments. This may be done to ensure lower complications of treatment, to better improve infertility treatment success, and to lower complications of pregnancy.

Currently, many infertility patients can be treated by assisted reproductive technologies (ART), in which fertilization of oocytes occurs in a laboratory environment. In vitro fertilization (IVF), the most common ART procedure, involves different stages for conception to occur, including oocyte retrieval from the ovaries, sperm introduction to oocytes, and successful transfer of embryo(s) back into the female for implantation. During the beginning of a cycle, follicle-stimulating hormone (FSH) injections are administered to patients during the follicular phase of the ovarian cycle to maximize the number of developing follicles. On days 12–14, a trigger shot, usually hCG (human chorionic gonadotropin), stimulates the final maturation of oocytes. Then, the matured oocytes are collected for fertilization in the laboratory. Once the oocyte is fertilized by the sperm to create a zygote, the embryo begins to divide. The embryo can be implanted in the uterus by day 3 or 5 after fertilization. Day 3 embryo cleavage comprises 6–9 cells that are in the process of dividing, but the embryo itself will not grow in size. Day 3 embryos can incubate further to day 5 blastocysts containing more advanced cellular structures. In situations where the quality of sperm is not optimal, intra-cytoplasmic sperm injection (ICSI) technique may be used to inject one sperm into the oocyte to increase the chances of successful fertilization.

### *Impact of Body Mass Index (BMI) on Retrieval of Oocyte Numbers in* In Vitro *Fertilization… DOI: http://dx.doi.org/10.5772/intechopen.111781*

A significant number of IVF and ICSI babies have been born throughout the world. However, a key factor of assisted reproductive techniques is the reliance on medicine and hormones to stimulate the ovaries to develop multiple follicles per cycle. Nonetheless, some patients may show less than optimal responses to the medication prescribed. One reason may be due to high and low BMIs. As a result, the number of retrieved oocytes, oocyte maturity, subsequent fertilization, embryo quality, and live birth rates may be reduced. Overweight women tend to have lower responses to medication to regulate and/or initiate ovulation, resulting in higher doses. In addition, women who are overweight/obese have a greater frequency of over-response and a higher risk of overstimulation. If a multiple pregnancy occurs, there are greater obstetrical complications in patients with higher BMIs than that of normal range BMIs. Additional complications include fewer eggs retrieved, increased difficulty during the retrieval process, increased risk of bleeding, increased risks of anesthesia, and greater difficulty during embryo transfer when visualizing the uterus.

Likewise, underweight individuals experiencing anorexia nervosa or bulimia are potentially at risk for infertility [2]. In patients who are malnourished or starving, a lowered metabolic rate, along with decreased gonadotropin release, may result in fertility loss. Deficiencies in estradiol, an important player in the female reproductive system that is commonly seen in anorexia is also due to low ovarian stimulation. As a result, patients who are underweight are advised to gain weight prior to starting fertility treatment.

Although previous studies have reported that being underweight or overweight/ obese has significant effects on female fertility, there are no reports analyzing the effect of body weight on fertility factors, such as the number of oocytes retrieved and fertilized, embryo quality, and IVF outcomes. Therefore, this study is designed to examine the impact of body weight on fertility treatment outcomes. The goal of this study is to determine if fertility is impacted by individuals who are underweight, overweight, or obese by analyzing IVF outcomes so that practitioners may correctly counsel their patients before undergoing assisted reproductive technology.

### **2. Materials and methods**

This was a retrospective study in an IVF laboratory. The deidentified data was collected from patients who have undergone IVF treatment in 2016 at the Reproductive Health Center in Tucson, Arizona. Information regarding patient IVF procedures includes: patient age, weight, height, number of retrieved oocytes, number of matured oocytes, number of embryos created, number of embryos transferred, pregnancy rates, and live birth.

Data for underweight and overweight patients were compared to individuals within the normal weight range. Body mass index (BMI) of each patient was calculated. The normal range is 18.4–24.9, whereas an underweight value is below 18.4. Overweight values range from 25 to 29.9. Obese values have BMIs of 30 or greater. BMI was calculated by an individual's weight divided by their height squared (kg/m2 ). Using these ranges, the infertile patients were grouped into four categories (underweight, normal, overweight, and obese).

Prior to the procedure, various hormones, including gonadotrophin-releasing hormone/follicle-stimulating hormone (GnRH/FSH) injections (250-450IUs depending on patient age and BMI), were given to the patients to target the growth of follicles during an IVF cycle. Based on follicular size and blood estradiol level, at 36–37 hours after human chorionic gonadotrophin (hCG, 4000 to 10,000 IU) administration for oocyte maturation, the eggs were retrieved from ovaries through transvaginal by our physician standardized procedure. Therefore, the retrieved oocytes were classified as matured oocytes (MII), germinal vesicle (GV), postmatured oocytes, or degenerate oocytes. Only matured oocytes (MII) were used to calculate maturation percentage rate.

## **2.1 Statistical analysis**

The average and standard deviation (means) of all data were calculated by Microsoft Excel. The significant differences between the averages were examined by student t-test statistical analysis, and the difference between the percentages was examined by percentage test method. The differences were considered statistically significant at p < 0.05.
