World Applied Sciences Journal 23 (7): 935-937, 2013
© IDOSI Publications, 2013
Corresponding Author: Leila Sekhavat, Obstetrics and Gynecologist, Shahid Sadoughi University of Medical Sciences,
Yazd, Iran. Tel: +983518224001, +989131525637, Fax: +983518224100.
Relationship Between Fetal Sex and Nausea
and Vomiting During Pregnancy
Fatemeh zare and Leila Sekhavat
Obstetrics and Gynecologist, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
Submitted: May 8, 2013; Accepted: Jun 13, 2013; Published: Jul 19, 2013
Abstract: Nausea and vomiting of pregnancy (NVP) affects approximately 80% of pregnant women. Its cause
remains largely undetermined. The aim of this study was to assess the effect of fetal sex on tendency of NVP.
A population-based study comparing all singleton pregnancies of patients carrying male and female fetuses
was performed in Shahid Sadoughi hospital, Yazd, Iran from May 2010 to April 2011. Data were obtained
from maternal self-reported information and prenatal care records during the first visit (<16 weeks of gestation).
We get the offspring sex ratio of all births and compared in mother with history of NVP and none.
Statistical analysis was performed with the SPSS software and differences were considered significant at P
values < 0.05. Results revealed that during the study period 2450 deliveries were occurred in our hospital.
There were no significant differences between the groups regarding maternal age, gestational age, gravida,
education and mother employment. There were 1241 (50.6%) deliveries of male and 1209 (49.4%) deliveries of
female gender. NVP was reported by 1862 women (76%) and approximately half of which had been vomiting.
The rate of NVP was higher in women with male fetuses than female fetuses (79.5% vs72.3%)..In conclusion,
this study showed that women presenting with NVP are more likely to have a male fetus than female.
Key words: Fetal Sex Nausea And Vomiting Of Pregnancy HCG Concentration
INTRODUCTION with thyroxin, prostaglandin E2 and prolactin as possible
Nausea and vomiting of pregnancy (NVP), commonly physicians were taught that psychological factors are
known as "morning sickness," affects approximately 80% responsible for NVP . Maternal diseases like
of pregnant women . NVP commonly occurs between hypertension or renal diseases and stress shown to be
5 and 18 weeks of pregnancy. Between 50 and 90 percent related to the risk of NVP. Some studies found that
of women have some degree of nausea, with or without presence of NVP is associated with older maternal age,
vomiting. This sickness is generally a mild, self-limited BMI, employment as manual or service workers, maternal
condition that may be controlled with conservative smoking and infant gender . Reproductive history
measures . A review of evidence-based management of including increasing gravidity and having multiple prior
nausea and vomiting in pregnancy found that these miscarriages have also been reported to increase the risk
discomforts have a profound effect on women’s health for NVP .
and quality of life during pregnancy and early recognition Throughout history, people have tried to predict the
and active treatment is warranted because it can be sex of their offspring. More than 2000 years ago,
associated with adverse healthy effect in both fetus and Hippocrates stated that female fetuses give the mother a
mother . pale face, whereas a mother carrying a male fetus has a
The etiology of NVP remains unclear, but many healthier tone to her skin. Despite efforts to find reliable
reports have suggested that hormones may cause nausea physical signs or symptoms during pregnancy to
and vomiting of pregnancy. Rises in human chorionic indicate the sex of the offspring, none have been found.
gonadotropin (HCG) and estrogens are likely contributors, Some studies reported that pregnant women with a
additional contributing factors . Although many
World Appl. Sci. J., 23 (7): 935-937, 2013
diagnosis of hyperemesis gravidarum in the first trimester Data were obtained from maternal self-reported
give birth to a higher proportion of female newborns than information and prenatal care records during the first visit
do all mothers. (<16 weeks of gestation). We get the offspring sex ratio of
There is little information on the relation between all births and compared in mother with history of NVP and
infant gender and NVP [8- 10]. According to previous none.
studies, it has been suggested that elevated human All analyses were performed with the use of SPSS
chorionic gonadotropin (HCG) is associated with NVP . version 16 statistical software. Chi-square test or Fisher
A fetal sex-related effect on HCG concentration in exact test were used for data analysis of qualitative
singleton pregnancies has also been reported. Pregnant variables and mean values were compared using ANOVA.
women carrying female fetuses have higher HCG levels Risks were expressed as odds ratios (OR). Ninety-five
than women carrying male fetuses. percentage confidence intervals (95%CI) using
In this study, we prospectively evaluated association Miettinen's method. Differences were considered
between fetal sex and NVP. significant at P values < 0.05.
MATERIALS AND METHODS RESULTS
In a population-based study, we identified all During the study period 2450 deliveries were
singleton pregnancies that delivered a live born baby amitted in our hospital. There were 1241 (50.6%)
between September 2010 and August 2011 in Shahid deliveries of male and 1209 (49.4%) deliveries of
Sadoughi hospital, Yazd, Iran and had a pervious female gender. NVP was reported by 1862 women
diagnosis of NVP in early of pregnancy. (76%) and approximately half of which had
This study has been approved by the ethic committee been vomiting. One Thousand five hundred and ten
of Shahid Sadoughi University of Medical Sciences, Yazd, (81%) of NVP had occurred in the first trimester of
Iran and all the participants gave written informed pregnancy.
consent. The survey results were kept confidential. Table 1 showed that there was no difference in the
Eligible participants included mothers who maternal medical characteristics of both female and male
remembered their prenatal care history and had a normal newborns groups.
singleton pregnancy. Exclusion criteria were who had Totally, the rate of NVP was higher in women with
known maternal disease (upper gestational tract disease, male fetuses than female fetuses [(79.5% vs 72.3%)
vestibular disease, liver disease, or hyperthyroidism), (P<0.05)] (Table 2). Among women with NVP in the first
Under 18 years old or more than 40 years’ old women and trimester, the proportion of female fetuses was higher than
multiple pregnancies. males.
Table 1: Comparison of maternal characteristics with NVP based on fetal sex
Male n =1241 Female n =1209 P.Value
Maternal age in year : Mean ± SD 24.4±5.8 25.4±6.1 0.3
Gestational age in week :Mean± SD 38.9±1.5 38.2±1.1 0.2
Mother employment Yes [N (%)] No [N (%)] 664 (53.8) 573(46.2) 0.08
Gravida Primigravida [N (%)] 411(33.1) 435 (36) 0.06
Multigravida [N (%)] 830 (66.9) 774 (64)
Education in years <12 [N (%)] 214(17.2) 203(16.8) 0.08
12 - 16 [N (%)] 589 (47.5) 608(50.3)
>16 [N (%)] 438(35.3) 398(32.9)
Table 2: Proportion of fetal sex in Women with NVP Compared with all Births
All births 2450 Male n =1241 Female n =1209 P value
NVP [N(%)] 987 (79.5) 874 (72.3) 0.03
Vomiting [N(%)] 451 (39.9) 482 (39.2) 0.01
World Appl. Sci. J., 23 (7): 935-937, 2013
The present study has evaluated the relationship
between fetal sex and NVP and the result of study showed
an increased proportion of male fetuses among women
who have NVP.
For years now, there has been a constant debate
about whether or not nausea and vomiting during
pregnancy determines baby gender. Many women claim
that they experience worse morning sickness when
they carry boys, while others claim that their nausea
and vomiting was more severe when they carried girls.
The investigators suggest that raised concentration of
human chorionic gonadotropin (HCG) is associated
with hyperemesis gravidarum. Tamay and K.Ku çu, .
In normal pregnancies female fetuses are associated
with higher HCG concentrations at birth than male
fetuses. It has been suggested that maternal serum human
chorionic gonadotropin (HCG) levels are influenced by
the sex of the fetus and specifically that HCG
concentrations in maternal blood and placenta tissues are
higher when the fetus is female. Del Mar Melero-Montes
and Hershel . Contritely in our study, there were more
female fetuses in the first NVP but generally there were
more male fetus in NVP. Studies have suggested that
offspring of women hospitalized for hyperemesis
gravidarum have a different sex ratio than those of
women without this diagnosis, but little is known of the
potential association between fetal gender and NVP
[8, 12]. Recent studies reported that women presenting
with morning sickness are more likely to give birth girls
than boys [13, 14]. He has considered morning sickness
is a sickness of first trimester of pregnancy. It is similar to
Our findings provide evidence that pregnant women
with a diagnosis of NVP in the first trimester give birth to
a higher proportion of male newborns than do all mothers.
We would like to thank residents and staff of
obstetric clinic of Shahid Sadoughi University of Medical
Sciences, Yazd, Iran for helping in gathering of data and
thank Department of Statistics for helping in data
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