Obesity can impair reproduction in both women and men, leading to infertility in couples trying to conceive, cause subsequent complications in pregnancy, and adverse effects on their offspring.
In women with excess weight, abdominal fat increases the risk of having menstrual abnormalities. Obese women in the general population have a higher incidence of menstrual irregularity, and lower chance of conception within one year of stopping birth control compared with normal weight women. Obesity is often associated with abnormal ovarian function. Pregnancy rates frequently improve after weight loss in obese women who do not ovulate (anovulatory).
Moreover, obesity effects how much medicines may be needed to obtain optimal ovarian stimulation. It is associated with requiring higher doses of medication (follicle stimulating hormone/FSH) to induce ovulation or stimulate the ovaries for in vitro fertilization.
Additionally, this can result in fewer mature follicles and a decreased chance for oocyte retrieval. Similarly, in women presumed to be ovulatory who are undergoing donor sperm insemination, findings show that increased abdominal obesity impairs conception. In other studies, obesity has reduced embryo implantation, reducing the age adjusted live birth in a BMI dependent manner. It has been shown that obesity alters oocyte morphology, reduces fertilization in some, and impairs embryo quality in women less than 35 years of age. Specifically, women with a BMI more than 25 have smaller oocytes that are less likely to complete development post fertilization, with the embryo(s) arrested before blastocyst formation.
Obese women undergoing Invitro Fertilization (IVF) also have a reduced chance of clinical pregnancy and live birth as compared with normal weight women. Several studies have shown that overweight women undergoing IVF have a 10% lower live birth weight than women of normal weight. At the uterine level, obesity appears to alter endometrial receptivity during IVF. This is seen when third-party surrogate women with a BMI of more than 35 demonstrate lower live birth rates compared with those with a BMI of less than 35.
Obesity is also linked with increased pregnancy loss in many studies. In a pregnancy conceived through IVF, maternal BMI positively correlated with the risk of spontaneous abortion. These findings support the view that a high BMI of more than 40 have an increased risk of biochemical and spontaneous pregnancy loss compared with lean women. Maternal prenatal obesity is associated with pregnancy and perinatal complications including gestational diabetes, hypertension, preeclampsia, preterm delivery, stillbirth and Cesarean section.
On the male side, not all obese men are infertile. But those who are can have reduced semen quality, erectile dysfunction, and physical problems including sleep apnea. In obese men, the scrotum remains in closer contact with the surrounding tissue than the normal weight men, predisposing increased scrotal temperature that may adversely affect semen parameters. Weight reduction in obese men can improve total sperm count and morphology as well as increase SHBG and total testosterone.
Management or lifestyle modifications may include a weight management program that focuses on preconception weight loss to a BMI of less than 35.
Metformin, a frequently prescribed medicine for diabetes and Polycystic Ovarian Syndrome (PCO) is not associated with weight loss, however when metformin is combined with a low calorie diet, weight loss has been demonstrated.
Bariatric surgery is one of the most commonly recommended procedures which might help people to lose weight in a more regular controlled manner with a lower possibility of regaining the lost weight.
Keeping in mind these negative effects of obesity, it’s recommended to start early lifestyle changes for both men and women which may include a preconception consultation with a dietitian, and medical therapy as another added resource for weight loss if needed. If bariatric weight loss surgery needs to be performed, the usual recommended wait to conceive is at least one year.
It is important to consider the risk of declining fertility with age related decrease prior to any obesity treatment.
In conclusion, while most obese women and men are fertile, obesity in women is associated with ovulatory dysfunction, reduced ovarian response to ovulation, altered oocytes as well as endometrial function and low birth rates. Obese women are also at higher risk of developing maternal and fetal complications during pregnancy
It is important for obese couples to address and determine a plan for weight management as part of an infertility evaluation and treatment planning. The healthier the parents, the better outcome for a healthy conception and child.
Adopted from ASRM