Intro
Menstruation is a cyclic endometrial desquamation resulting from the interactions of
hormones produced by the hypothalamic-pituitary-ovarian axis. The integrity of the
hypothalamic-pituitary-ovarian axis is essential for ovulation and regular menstrual
cycles, and external factors may influence this complex feedback system ( Speroff & Fritz, 2005 ). Since the primary
function of the menstrual cycle is to promote a woman's reproductive capacity,
changes in this cycle impact on female fertility. Rogers & Mitchell (1952) demonstrated an association between
menstrual changes, excess weight, infertility, and recurrent miscarriages.
Therefore, studies on the association of menstrual irregularity and obesity are
long-standing; however, many of these studies have been limited because of their
small sample size and the participants have gynecological problems or are
participating in weight reduction programs.
Obesity is one of the factors that can influence the menstrual cycle. It can be
defined as a disease characterized by excessive accumulation of body fat, due
positive energy balance, causing health effects, with significant loss in quality
and lifetime. One of the classifications of obesity was proposed by the World Health
Organization ( WHO, 2015 ). Several
pathophysiological disorders are caused by obesity, especially in people with Body
Mass Indexes (BMI) above 30 kg/m 2 . Cardiovascular disorders, endocrine
and metabolic disorders, respiratory disorders, gastrointestinal disorders,
dermatological disorders, musculoskeletal disorders, neoplasia psychosocial
disorders, increased surgical and anesthetic risk, decreased physical agility and
disorders in pregnancy and fertility, as absence of ovulation ( Tavares et al ., 2010 ). In the United States,
about 68% of the adult population is overweight, and about 34.9% are obese ( Ogden et al ., 2014 ). According
to the Brazilian Ministry of Health, in the adult population in Brazilian capitals,
overweight prevalence is of 49.1% among women. In Goiânia, the state capital
of Goiás (Brazil), 48.1% of women are overweight and 16.3% are obese ( Brazil-Ministério da Saúde,
2015 ).
Some studies have used self-reported height and weight; and the definitions of
menstrual regularity vary according to each study. Much of this research is limited
to overweight and obese patients associated with Polycystic Ovarian Syndrome (PCOS).
Due to the increasing prevalence of overweight and obesity, it is important to
investigate its effects on the reproductive health of women, and to better quantify
the strength of associations with menstrual irregularity ( Wei et al ., 2009 ). The early onset of obesity,
especially in adolescence, favors the development of irregular cycles, oligo/chronic
anovulation and infertility in adults ( Pasquali
& Gambineri, 2006 ). In addition to the deleterious effects of obesity
on female reproductive function, such as delay in spontaneous conception, higher
prevalence of infertility and natural abortions, there is still a worse response to
infertility treatments and a higher prevalence of obstetric complications ( Pasquali & Gambineri, 2006 ; Nelson & Fleming, 2007 ).
The subject of this study was the ecograph assessment of ovulation and menstrual
cycle parameters, associating them to higher BMI in infertile patients. The problem
is the high prevalence of overweight and obese women in the world, in Brazil and
also in Goiânia, and the repercussions on their health, especially in
relation to their reproductive health. There is also an increase in childhood
obesity, and there may be an increase in sub and infertility in the future. This
study is justified, because although there are several worldwide studies on
menstrual irregularity and obesity, there are few with hospital samples involving
assisted reproductive clinics accompanying the cycle and ovulation of these patients
through the monitoring of ovulation, and the great majority is patients with obesity
and PCOS concomitantly.
Due to the increasing prevalence of overweight and obesity, it is important to
investigate their effects on the reproductive health of women and quantify the
strength of association with ovulation and menstrual irregularity ( Wei et al ., 2009 ). Since
menstrual regularity is closely associated with endocrine physiology and ovulation,
the assessment of the association of these factors with body mass index (BMI) will
help on this quantification. Various researches invariably associate obesity with
polycystic ovaries thus creating a bias. We reinforce that patients with polycystic
ovaries are not included; demonstrating that obesity alone is an association factor
to anovulation. The objective of this study is to assess whether there is an
association between the presence or absence of ovulation and the presence of
overweight/obesity calculated by BMI in infertile patients without Polycystic Ovary
Syndrome, in a university service.
Results
After assessing the statistical tests of case and control groups to see if they were
comparable, we found out that the variables matched, so the groups were paired;
thus, there was no need for adjustments ( Table
1 ).
Characteristics of the two study groups. Lab Rep HC/UFG 2016
Lab Rep HC/UFG= Human Reproduction Laboratory of the Clinica's Hospital;
n=number;
Mann-Whitney test;
t-Test
The height of anovulatory patients ranged between 1.40 and 1.80 m
( x =1.60±0.07), the weight between 41.5 and 105kg
( x =65.60Kg±12.52) and BMI ranged between 18.11 and
38.96kg/m 2
( x =25.64±4.24Kg/m 2 ). In the group of
ovulatory patients, height was between 1.45 to 1.73m
( x =1.60±0.063), weight between 45.2 and 97.5Kg
( x =63,29Kg±10.77) and BMI between 18.25 and 36.40
kg/m 2 ( x =24,76Kg/m 2 ±3.81).
Table 2 and Figure 2 depict the distribution of patients, according to ovulation,
categorized by BMI. From a total of 228 patients monitored, 110 were anovulatory and
118 were ovulatory. Among the anovulatory patients, 57 (51.82%) were overweight;
while among ovulatory patients, 44 (37.29%) were in this same BMI category. The odds
ratio was 1.8087, with a significant p value
( p <0.05).
Distribution of 228 patients according to ovulation, categorized according to
BMI. Lab Rep HC/UFG 2016.
Lab Rep HC/UFG= Human Reproduction Laboratory of the University Hospital;
n= number;
X 2 = 4.871, Pearson’s test; OR= Odds
Ratio ; CI= Confidence Interval.
Figure 2 Distribution of 228 patients according to ovulation categorized by BMI.
Lab Rep HC/UFG 2016
Distribution of 228 patients according to ovulation categorized by BMI.
Lab Rep HC/UFG 2016
Discussion
Infertility is a disease of the reproductive system, defined by the inability to
achieve clinical pregnancy after 12 months or more of regular and unprotected sexual
intercourse ( ASRM, 2013 ). WHO estimates that
48.5 million couples worldwide are infertile. Ovulatory infertility can reach up to
a quarter of infertility etiologies. Since obesity affects ovarian function,
evaluating body mass parameters are very relevant for infertile patients ( Mascarenhas et al ., 2012 ;
Nardo & Chouliaras, 2015 ). Ovulation
sets the cycle regularity, and both int raovarian factors regulate folliculogenesis,
and there should be a balance between them. Any imbalance between the extra and
intra ovarian factors may result in abnormal folliculogenesis ( NICE, 2013 ). However, the clinical evaluation of menstrual
regularity, may not be a reliable parameter for the diagnosis of ovulation. The
assessment of ovulation by ultrasound provides for a more accurate diagnosis of
ovulation ( Frank et al .,
2008 ).
Obesity is a complex and multifactorial disease, developed by the interaction between
the person's genotype and the environment ( Malcolm
& Cumming, 2003 ; NHI, 2000 ).
The most obese women do not have fertility disorders, but obesity may negatively
influence their menstrual cycle and fertility; and one mechanism, is the absence of
ovulation ( ASRM, 2008 ). Beyond its risks
during pregnancy, obesity on puerperium is associated with the occurrence of
infectious complications in the postpartum period, such as infection of surgical
wounds, urinary tract infection and need for antibiotics ( Chin et al ., 2014 ).
The study was carefully concocted, and the selection bias was mitigated by the
strictness of the inclusion and exclusion criteria. Group comparability was ensured
by the assessment of pairing the possible confounding variables. The observer bias
was mitigated because there was blinding about the exposure factor in both the study
group and the control group, avoiding bias in information collection. Although most
obese women do not develop infertility, when obesity influences cycle control and
ovulation, it can have a negative impact on female fertility ( Paiva et al. , 2012 ). With the increasing
prevalence of obese and overweight children and women, the interference of those
with menstrual regularity, and consequently on fertility, acquires greater
importance. There are many studies involving infertile patients with overweight and
obesity, but the samples in most cases include or are limited to patients with
polycystic ovaries. In this study, the lack or absence of ovulation was assessed by
analyzing the body mass index of patients, excluding those with polycystic
ovaries.
Our results were coincident with many studies in the literature, such as Kuchenbecker et al . (2010) , who
reported an association between anovulation and overweight. It also corroborated by
other studies that indicate an increased risk of oligo and anovulation in obese
women, such as those from Brewer & Balen
(2010) and Oliveira & Lemos
(2010) , even among those women who have regular menstrual cycles. Obesity
was also associated with oligomenorrhea and anovulation by Yilmaz et al . (2009) . The chance of patients
with higher-than-normal BMI not ovulating is about 1.8 times greater than among
normal BMI individuals.
It is possible that both the excess weight and infertility be symptoms of the same
pathology. Although obesity decreases fertility, it is unclear how much weight loss
could increase it in overweight patients ( Koning
et al., 2010 ). The fertility treatment in subfertile
women with overweight and obesity differs between countries and treatment centers.
In some centers in the Netherlands, overweight women are not treated at all. At
other fertility centers, overweight and obese women are treated regardless of their
BMI. The British Fertility Society inform women with a BMI above 30 kg/m 2
that they tend to take longer to get pregnant, and if they are not ovulating weight
loss increases the chances of conception. While there is enough convincing evidence
that weight reduction eventually leads to more spontaneous pregnancies, the main
goal is to reduce the complications of excess weight during pregnancy ( NICE, 2013 ).
The American Society for Reproductive Medicine and the American College of Obstetrics
did not publish guidelines for clinical management of obese infertile patients
( Vahratian & Smith, 2009 ). The
institutions that restrict the treatment of overweight patients justify the
restrictions because of high costs and limited funding for the procedures,
decreasing success and increasing risk of complications during pregnancy ( Koning et al., 2010 ).
Restrictions on fertility treatments in patients with high BMI often do not address
issues of justice and may violate a woman's right to autonomy. Those patients with
increased BMI can be discriminated and without access to treatment.
Our study indicates that patients with excess body mass, without other diseases, were
associated with anovulation. This is a contribution to clarify these issues. We
considered as a limiting factor, the fact that in our study, monitoring of ovulation
is performed in a single cycle, and there may be variations between the follicular
growth cycles in the same woman. However, monitoring during one cycle only is the
procedure adopted by most human reproduction services ( Mikolajczyk et al ., 2008 ).
Conclusions
There was an association between the lack of ovulation upon ultrasound monitoring of
the ovulation cycle and increased body mass index, with higher anovulation risk in
patients above normal weight, even if they did not have polycystic ovaries.
Materials|Methods
This was a case-control study performed at the Human Reproduction Laboratory of the
University Hospital (Lab Rep HC/UFG). We evaluated 1,356 monitoring of basal
ovulation, without stimulation with ovulation inducers, performed between January
2011 and December 2015. For "n" calculation, with 80% power test, the number of
cases and controls needed was 105 each.
After collecting the data from the ovulation monitoring form, we selected the cases
as the anovulatory patients in the cycle. The study included patients with
infertility for at least one year, aged 18 to 38 years, no more than 10 mm follicle
on 1 st examination, antral follicle count between 3 and 12 in each ovary
counted between the 2 nd and the 5 th day of the cycle, absence
of prior cystectomy or oophorectomy, and endometriomas absence. We selected 148
cases.
The control group, consisting of reports of patients who ovulate on the monitored
cycle, was randomly selected, and we applied the same inclusion criteria used for
the group of cases. Ovulation in the control group was considered only in those
cycles in which the follicle reached at least 16 mm in diameter. The disappearance
or decrease of at least 70% of the diameter was considered follicular collapse. We
selected 154 controls.
Later, we assessed the medical records of patients. The inclusion and exclusion
criteria were based on the fact that they are factors that influence the menstrual
cycle and fertility of women (confounders). After applying the exclusion criteria,
we ended up having 110 cases (patients who did not ovulate on the monitored cycle),
and 118 controls (patients who ovulated on the monitored cycle). The exclusion
criteria were patients with low body weight (BMI <18.5 kg/m 2 );
follicle stimulating hormone (FSH) above 10IU/L; stages III and IV endometriosis
diagnosis, Thyroid Stimulant Hormone (TSH) lower than 0.4 or higher than 4.5mU/L;
prolactinaemia above 20 ng/ml; diagnostic Polycystic Ovary Syndrome and smokers. At
this point we had access to BMI data of patients, checking for the presence or
absence of exposure factors (overweight/obesity). Henceforth, the presence of
overweight or obese patients will be considered "BMI above normal".
The ovulatory status of the study variables was: absence or presence of a monitored
ovulation in the cycle. The exposure variables were: normal BMI or patients
classified with a BMI above normal ( Figure
1 ).
Figure 1 Flow chart assessing the presence of ovulation in overweight and normal
individuals. Lab Rep HC-UFG 2016
Flow chart assessing the presence of ovulation in overweight and normal
individuals. Lab Rep HC-UFG 2016
The patients were classified according to BMI, following the WHO’s definition of body
mass (18.5 to 24 kg/m 2 ), and above normal (>25 kg/m 2 )
( WHO, 2015 ).
The patients were subjected to biometric examination, assessing height and weight on
a WELMY, W110H model scale. Ovulation monitoring was performed on the 2 nd
to the 5 th day of the cycle, with new measurements from the
10 th day of the cycle until ovulation occurs, or until day 16 if
there is no dominant developing follicle(s) or follicular collapse. Antral follicles
were counted following the technical recommendations of Broekmans et al . (2010) between the
2 nd and the 4 th day of the spontaneous menstrual cycle.
The ultrasound equipment used was the LOGIQ P6 model, manufactured by General
Electrics (GE). The examinations were performed by physicians from the Human
Reproduction Laboratory HC-UFG.
Comparability between the case and control groups was confirmed by checking the
pairing of the following variables: age (years); age at first menstruation
(menarche); number of pregnancies; number of children born up to 22 weeks of
gestational age (Parity); number of abortions; the number of antral follicles
between the 2 nd and 5 th day of the cycle; having bilateral
tubal ligation (BTL)and the laboratory test values of FSH (IU/L), prolactin (mcg/L)
and TSH (mU/L).
In order to compare the mean values between the case and control groups, because they
were two unrelated groups, we chose the t-test for independent samples as a
parametric test for the variables with normal distribution and the Mann-Whitney test
as a non-parametric test for variables with non-normal distribution ( Mann & Whitney, 1947 ).
To assess whether the patients in the case group and the control group had a
different BMI on the WHO classification between normal weight or overweight, we used
the Pearson’s performed chi-square statistical test (χ 2 ) and
calculated the Odds Ratio. For the statistical analysis we used the SPSS 22.0
software.
In the study, we used the database of medical records of patients from the Human
Reproduction Laboratory of the Clinica's Hospital, Federal University of
Goiás. No informed consent of patients was needed. The study was approved by
the Ethics Committee of the Clinica's Hospital, Federal University of Goiás
under number 1,235,590.
Text is read by the "Ask this paper" AI Q&A widget below.
Extraction quality varies by source — PMC NXML preserves structure
cleanly, OA-HTML may include some navigation residue, and OA-PDF can
have broken hyphenation. The publisher copy
(via DOI)
is the canonical version.