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\begin{document}

\title{ASSESSMENT OF MATERNAL ABDOMINAL SUBCUTANEOUS FAT THICKNESS (SFT) AS AN
INDEPENDENT PREDICTOR OF ADVERSE PREGNANCY OUTCOMES: A PROSPECTIVE
COHORT STUDY}



\author[1]{NILA SURENDRAN}%
\author[1]{PRATIKSHA GUPTA}%
\author[1]{utkarsha agarwal}%
\author[1]{PALLAVI SHEKHAWAT}%
\affil[1]{Guru Gobind Singh Indraprastha University}%


\vspace{-1em}



  
  \date{May 25, 2024}


\begingroup
\let\center\flushleft
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\selectlanguage{english}
\begin{abstract}
\textbf{Introduction:} Obese pregnant women are at increased risk for a
variety of maternal and perinatal complications. The maternal risks
related to obesity include Gestational Diabetes mellitus, Preeclampsia,
increased caesarian sections. The fetus is at risk of stillbirth,
preterm birth and congenital anomalies.This study focuses on the use of
Maternal abdominal subcutaneous fat thickness (SFT) as a surrogate
measure for central obesity as measured by ultrasound, and determining
its efficacy compared to BMI in predicting obesity related pregnancy
complications. \textbf{Objective:} To measure mid-trimester SFT in
antenatal women and establish SFT as an independent predictor of obesity
related adverse pregnancy outcomes \textbf{Methods:} This was a
prospective cohort study. 150 pregnant women between 20-40 years of age
were recruited. Demographic data of each participant was collected from
the OPD. USG for abdominal subcutaneous fat thickness (SFT) was done at
18-22 wks period of gestation.The participants were followed up to
labour. Adverse pregnancy outcomes and their correlation with the SFT
measured was studied. \textbf{Results:} There was significant positive
correlation between BMI and SFT (r=0.591, p\textless{}0.001) .A positive
correlation was noticed between BMI and adverse pregnancy outcomes such
as PIH, GDM , preterm birth , postdatism and NICU admissions.SFT
independently showed a positive correlation with the above parameters.
The mean SFT among women without PIH was 11.45 mm, and with PIH was
16.48 mm{[}p \textless{}0.001{]}.Mean SFT were 11.68mm and 16.24 mm
among the ladies without and with GDM
respectively{[}p\textless{}0.001{]}. The mean SFT for term pregnancies
was 12.06 mm whereas the mean SFT for preterm births was 14.21 showing
positive correlation between SFT and preterm birth. SFT also showed
positive correlation with need for NICU admission for neonates {[} SFT
avg being 11.72mm and 14.94 mm in the 2 groups{]}. A comparative
analysis was done between BMI and SFT regarding their correlation to the
various outcomes. SFT showed higher correlation coefficients for these
variables than BMI, with lower p values suggesting more statistical
significance. \textbf{Conclusion:} BMI showed a positive correlation
with adverse pregnancy outcomes in mother as well as fetus, SFT showed
greater and more statistically significant correlation for adverse
outcomes. Thus it was concluded that SFT is a better independent
predictor of obesity related adverse pregnancy outcomes.%
\end{abstract}%



\sloppy


\textbf{ASSESSMENT OF MATERNAL ABDOMINAL SUBCUTANEOUS FAT THICKNESS
(SFT) AS AN INDEPENDENT PREDICTOR OF ADVERSE PREGNANCY OUTCOMES: A
PROSPECTIVE COHORT STUDY}*NILA SURENDRAN\textsuperscript{1}, PRATIKSHA
GUPTA , UTKARSHA AGGARWAL, PALLAVI SHEKHAWAT ESI PGIMSR , Basaidarapur,
New Delhi,India ABSTRACT\textbf{Introduction:} Obese pregnant women are
at increased risk for a variety of maternal and perinatal complications.
The maternal risks related to obesity include Gestational Diabetes
mellitus, Preeclampsia, increased caesarian sections. The fetus is at
risk of stillbirth, preterm birth and congenital anomalies.This study
focuses on the use of Maternal abdominal subcutaneous fat thickness
(SFT) as a surrogate measure for central obesity as measured by
ultrasound, and determining its efficacy compared to BMI in predicting
obesity related pregnancy complications.\textbf{Objective:} To measure
mid-trimester SFT in antenatal women and establish SFT as an independent
predictor of obesity related adverse pregnancy outcomes\textbf{Methods:}
This was a prospective cohort study. 150 pregnant women between 20-40
years of age were recruited. Demographic data of each participant was
collected from the OPD. USG for abdominal subcutaneous fat thickness
(SFT) was done at 18-22 wks period of gestation.The participants were
followed up to labour. Adverse pregnancy outcomes and their correlation
with the SFT measured was studied.\textbf{Results:} There was
significant positive correlation between BMI and SFT (r=0.591,
p\textless{}0.001) .A positive correlation was noticed between BMI and
adverse pregnancy outcomes such as PIH, GDM , preterm birth , postdatism
and NICU admissions.SFT independently showed a positive correlation with
the above parameters. The mean SFT among women without PIH was 11.45 mm,
and with PIH was 16.48 mm{[}p \textless{}0.001{]}.Mean SFT were 11.68mm
and 16.24 mm among the ladies without and with GDM
respectively{[}p\textless{}0.001{]}. The mean SFT for term pregnancies
was 12.06 mm whereas the mean SFT for preterm births was 14.21 showing
positive correlation between SFT and preterm birth. SFT also showed
positive correlation with need for NICU admission for neonates {[} SFT
avg being 11.72mm and 14.94 mm in the 2 groups{]}. A comparative
analysis was done between BMI and SFT regarding their correlation to the
various outcomes. SFT showed higher correlation coefficients for these
variables than BMI, with lower p values suggesting more statistical
significance.\textbf{Conclusion:} BMI showed a positive correlation with
adverse pregnancy outcomes in mother as well as fetus, SFT showed
greater and more statistically significant correlation for adverse
outcomes. Thus it was concluded that SFT is a better independent
predictor of obesity related adverse pregnancy outcomes.\textbf{Key
words:} Obesity, Body Mass Index{[}BMI{]}, Subcutaneous Fat
Thickness{[}SFT{]}, GDM, Pre-eclampsia, Preterm

\textbf{INTRODUCTION}

Obesity is a medical condition where excess body fat has accumulated to
a level that it may have a negative effect on health of the person. The
proportion of global adult women with overweight has risen significantly
over the past 4 decades and the growing trend was observed in both high
income and middle income countries. In 2014, the percentage of female
with overweight and obesity in India was 21.7\%, and India had the
leading number of overweight and obese pregnant women (11.1\%) in
theworld\textsuperscript{1}. Obese pregnant women are at increased risk
for a range of maternal and perinatal complications, and the risks are
increased with increasing degrees of maternal obesity. The maternal
risks during pregnancy include mainly Gestational Diabetes mellitus and
Preeclampsia. The fetus is at risk of stillbirth, preterm birth and
congenital anomalies. Obesity in pregnancy can also affect wellbeing of
both mother and child later in life. For women, these risks include
heart disease and hypertension, while children have a risk of future
obesity and heart disease. Studies in recent years have highlighted that
the oocyte and/or early pre-implantation embryo is mostly vulnerable to
the effects of maternal obesity resulting in long-lasting endocrine and
metabolic effects for the offspring.\textsuperscript{2}There are a
number of methods to quantitatively define and categorize obesity. They
are -- 1. Body mass index (BMI): It is calculated by a person's weight
in kilograms divided by their height squared in meters. 2.
AbdominalCircumference

3\textbf{.} Body Fat Percentage

4. SFT (subcutaneous fat thickness) BMI is the most widely used
criterion. However, BMI has a disadvantage that it does not reflect fat
distribution or the ratio of adipose to non-adipose tissue. Other
disadvantages include not accounting for gender, ethnicity, muscle mass,
and frame size\textsuperscript{3}. Maternal abdominal subcutaneous fat
thickness can be used as a surrogate measure for central obesity and is
readily and accurately measured by ultrasound, a quick, safe modality
used routinely in pregnancy. Some recent studies demonstrated that
subcutaneous adiposity is associated with insulin
resistance\textsuperscript{4}.From retrospective studies there is some
indication that abdominal SFT at mid-pregnancy between 18- and 22-weeks'
gestation is superior to BMI to identify risk for obesity-related
pregnancy complications.

\textbf{OBJECTIVE}

We aimed at establishing Abdominal SFT (as measured by USG) and as a
novel, reliable marker to predict obesity related adverse pregnancy
outcomes.

\textbf{MATERIALS AND METHODS}

\begin{itemize}
\tightlist
\item
  Study design : prospective cohort study
\item
  Study setting: Obstetrics \& Gynaecology department of ESI PGIMSR and
  associated model hospital, Basaidarapur, NewDelhi.
\item
  Study period -- from December 2018 to February2020
\item
  The age of the study population -- 20-40yrs
\item
  Sample size --150
\end{itemize}

\textbf{PROCEDURE}

A prospective longitudinal cohort study was conducted in the department
of Obstetrics \& Gynaecology, ESI PGIMSR, New Delhi over a period of 2
years from 2018-2020. Pregnant women were recruited from the ante natal
OPD after meeting the inclusion and exclusion criteria.

\subsection*{INCLUSION CRITERIA}

{\label{inclusion-criteria}}

Pregnant women with singleton intrauterine pregnancy presenting to the
OPD in first trimester

\subsection*{EXCLUSION CRITERIA}

{\label{exclusion-criteria}}

\begin{itemize}
\tightlist
\item
  History of cardiovascular diseases
\item
  Diabetes mellitus
\item
  Chronic hypertension
\item
  Smoking
\end{itemize}

Demographic data was collected about each participant at the first
antenatal visit from the OPD; these included age, height, weight,
smoking habit, and parity. Informed consent was obtained from the
patients andrelatives.USG for abdominal subcutaneous fat thickness (SFT)
was done at 18-22 wks period of gestation. All scans were performed by
the same operator using a high-resolution multi frequency B-mode scan
2.5--5.0 MHz transducer. SFT measurements were performed in the midline
of the pelvis demonstrating uterus, cervix and placenta. Three measures
were taken from the skin line to the peritoneum, and the mean measure
will be used. The first measurement was done close to the midline and
two measurements were taken 5 mm on either side to take into account the
curvature from the ultrasound transducer face, ensuring the measurements
were done perpendicular to the anterior border. The calipers were placed
from skin line to peritoneal fascia. The participants were followed up
to labour.The following adverse pregnancy outcomes were observed and
their correlation with the SFT measured were studied:

\begin{enumerate}
\tightlist
\item
  pregnancy-induced hypertension
\item
  Gestational Diabetes Mellitus
\item
  Caesarian section
\item
  Preterm delivery (\textless{} 37 weeks POG)
\item
  postdatism
\item
  Neonatal respiratory distress and NICU admission
\end{enumerate}

The same outcomes were correlated with BMI .The women were stratified
into BMI categories according to World Health Organization (WHO).
Analysis was performed for BMI distribution and SFT measures.

\textbf{STATISTICAL ANALYSIS:}

Statistical testing was conducted with the statistical package for the
social science system version SPSS 17.0. Continuous variables were
presented as mean SD or median (IQR) for non normally distributed data.
Categorical variables were expressed as frequencies and percentages.
Correlation between BMI and SFT were done using Pearson correlation. For
all statistical tests, a p value less than 0.05 was taken to indicate a
significant difference.

\textbf{RESULTS}

In this study, the150 participants were divided into 4 categories
according to BMI: Underweight {[}BMI18.5{]}, Normal {[}BMI 18.5-24.9{]},
Overweight {[}BMI 25-29.9{]} and Obese {[}BMI \textgreater{}30{]}.We
compared the SFTvalues among the various BMI categories (underweight,
normal, overweight, obese). SFT 1, SFT2 and SFT3 are the measurements
taken in the same woman at 3 different points 0.5mm apart and SFT Avg is
the average value of the 3 measurements. The individual SFT measurements
as well as SFT average showed a linear relationship with BMI which was
statistically significant.{[}table 1{]} There was significant positive
correlation between BMI and SFT1 (r=0.590, p\textless{}0.001), SFT2
(r=0.595, p\textless{}0.001), SFT3 (r=0.587, p\textless{}0.001) and
average SFT(r=0.591, p\textless{}0.001) respectively{[}Table 2/ Fig
1.{]}. Since 'r' lies in between 0.50\textless{}r\textless{}0.60, it
shows that there was moderately positive significant correlation. The
incidence of PIH showed a positive correlation with obesity as measured
by BMI.SFT 1,SFT 2 ,SFT 3 and SFT Avg showed increasing values as we
moved from the group with no PIH( SFT Avg = 11.45 mm) to the group with
PIH (SFT Avg = 16.48mm), hence showing an average difference of 5mm
among the groups. This linearity had a p value of 0.001, hence being
statistically significant. {[}Tables 3\&4{]} The incidence of GDM
followed an increasing trend according to the maternal BMI. The figures
were 0\%, 6.7\%, 22.5\% and 44.4\% in UW, NORMAL, OW and OBESE groups
respectively. This pointed towards a strong association between GDM and
obesity with a p value of 0.001 which was significant.{[}Table 5/ Fig
2.{]} Likewise, comparison of SFT and GDM showed a positive correlation
between the 2 parameters. Mean SFT values were 11.68mm and 16.24 mm
among the groups without and with GDM respectively , hence confirming
that an increased SFT was a predictor of adverse pregnancy outcome such
as GDM. The finding was statistically significant as the p value was
\textless{}0.001.{[}table 6{]}Women with normal BMI showed term
deliveries in 93.3\% and preterm births in only 6.7 \%. This was less
compared to underweight category (16.6\%), overweight group (17.5\%) and
obese category ( 22.2\%). Hence the plot showed a J shaped curve, thus
showing a positive association of preterm birth with both underweight as
well as overweight/obese groups. However this association was not
statistically significant {[}p valueof0.163{]}.Whereas, the incidence of
preterm births showed a linear relation with SFT. The mean SFT for term
pregnancies was 12.06 mm whereas the mean SFT for preterm births was
14.21 mm showing an average increase of 2.2 mm in the preterm group.
{[}Tables 7 \& 8{]}This derivation also reached statistical
significance, with the p values of 0.036{[}SFT1{]} , 0.023{[}SFT2{]},
0.034{[}SFT3{]} and 0.032{[}SFTAVG{]}. Tables 9-10 show the correlation
of neonatal ICU admissions with obesity. An increasing trend was
observed with increasing BMI, though this observation was not
statistically significant. There was positive correlation between
maternal abdominal SFT measurement and the requirement of neonatal
Intensive care. It can be observed that the average SFT of mothers of
thoseinfantswhodidnotrequireNICUadmissionwas11.72mmwithastandarddeviationof3.09
mm. As against this ,the average SFT of mothers whose infants were
admitted in NICU was 14.94 with a standard deviation of 3.44 mm. Similar
trend was found among SFT1, SFT2 and SFT3 values(p=\textless{}0.001).
Finally the individual relationship of BMI as well as SFT with the
various parameters of the study were compiled {[}Table 11{]}. The
analysis was made using Spearman's correlation coefficient {[}ranging
from -1 to +1{]}. The variables taken were incidence of PIH, GDM,
Preterm, Postdatism, and NICU admissions. Their correlation coefficients
with BMI were 0.284, 0.266, 0.172, 0.147 and 0.157 respectively. In
comparison to BMI, SFT showed higher correlation coefficients for these
variables {[}0.454, 0.432, 0.226, 0.101 and 0.377 respectively{]}. The p
values were lower for SFT suggesting greater statistical significance.

\textbf{DISCUSSION}

In this study a significant positive correlation was established between
between BMI and mid-trimester SFT with a correlation coefficient of
0.591.this result was comparable to a study by Suresh A et
al\textsuperscript{5} which showed a correlation coefficient of 0.53.PIH
is classified as gestational hypertension, preeclampsia, eclampsia,
chronic hypertension with superimposed pre eclampsia. Gestational
hypertension is defined as BP higher than 140mm of Hg (systolic) or 90
mm of Hg (diastolic) on at least 2 occasions 4 hour apart in a woman who
had normal blood pressure prior to 20 weeks. Preeclampsia is diagnosed
when a woman with gestational hypertension also has proteinuria. The
incidence of PIH showed a positive correlation with increasing BMI.An
average of 5 mm increase in SFT measurements were seen in ladies with
PIH. The mean SFT among women without PIH was 11.45 mm whereas the mean
SFT of women with PIH was 16.48 mm .these values were statistically
significant , with a p value \textless{}0.001 , affirming the statement
that SFT can be an effective marker for prediction of PIH Gestational
diabetes mellitus (GDM) is defined as any degree of glucose intolerance
with onset or first recognition during pregnancy. The definition applies
whether insulin or only diet modification is used for treatment and
whether or not the condition persists after pregnancy. Numerous studies
across the world have reported an increased risk of gestational diabetes
mellitus (GDM) among women who are overweight or obese compared with
lean or normal-weight women.~A Meta -- regression analysis of 20 studies
done by SY Chu et al indicated that high maternal weight is associated
with a substantially higher risk of GDM\textsuperscript{6}. A more
recent prospective study by H Kansu-Celik\textsuperscript{7}and
colleagues showed a positive and significant correlation between a 50-g
GCT level and BMI, WC, and SAT thickness (\emph{p} \textless{} 0.001).
ROC curve analysis showed SAT {[}subcutaneous adipose tissue{]}
thickness above 16.75~mm predicted gestational diabetes mellitus (GDM)
with a sensitivity of 71.7\%, a specificity of 57.1\%.Similarly, in our
study a positive correlation between GDM and BMI with a p value of 0.001
was derived. Mean SFT were 11.68mm and 16.24 mm among the ladies without
and with GDM respectively, hence confirming that an increased SFT is a
predictor of GDM.Thepositive correlation of SFT with GDM and PIH were in
coherence with the results obtained from a study by Kennedy NJ et
al\textsuperscript{8} , which showed that with every 5mm rise in SFT
there was an increased risk of 22-24\% for GDM and 18\% for PIH. Preterm
is defined as babies born alive before 37 weeks of pregnancy are
completed. It is the leading cause of infant mortality, neonatal
morbidity, and long-term disability among non malformed infants, and
these risks increase with decreasing gestational age. Studies have
reported that women with obesity grades 2 to 3 (BMI [?]35) have increased
risks of very and moderately preterm delivery (\textless{}32 weeks and
32-36 weeks, respectively),\textsuperscript{9.10} while associations
between overweight (BMI 25-\textless{}30) and obesity grade 1 (BMI
30-\textless{}35) and preterm delivery are less
consistent.\textsuperscript{11,12} Two studies have also recently
reported an increased risk of extremely preterm delivery (\textless{} 28
weeks) among obese (BMI[?]30)women.\textsuperscript{13,14}In our study
,The plot showed a J shaped curve, thus showing a positive association
of preterm birth with both underweight as well as overweight/obese
groups.Also,there was a positive correlation with SFT. This was true for
all 3 SFT measurements. The mean SFT for term pregnancies was 12.06 mm
whereas the mean SFT for preterm births was 14.21 mm showing an average
increase of 2.2 mm among the 2 groups. This correlation also reached
statistical significance, with the p values of 0.036{[} SFT1{]} ,
0.023{[}SFT2{]}, 0.034{[} SFT3{]} and 0.032{[}SFT AVG{]}. Neonatal
outcomes were evaluated in terms of 3 parameters -- birth weight, APGAR
score at 1 min, and 5 min. The observations didn't show any definite
pattern as the values were comparable in all 4 groups. Increased
maternal BMI showed a rise in the requirement of neonatal Intensive care
within the first 24 hours. While 0\% of underweight mothers and 13.5 \%
of normal mothers had their neonates kept in NICU transiently, the
percentages of NICU admissions among overweight and obese mothers were
25\% and 33.3\% respectively. This correlation, however could not reach
statistical significance. There was significant positive correlation
between maternal abdominal SFT measurement and the requirement of
neonatal Intensive care. The average SFT of mothers of those infants who
did not require NICU admission was 11.72 mm while, the average SFT of
mothers of those infants who were admitted in NICU was 14.94 with a
standard deviation of 3.44 mm. This result was again comparable to the
previous Australian study by Kennedy NJ et al. When a final comparison
of BMI and SFT was done as independent markers of the above outcomes,
SFT showed higher correlation coefficients for these variables ie,
0.454{[}PIH{]}, 0.432{[}GDM{]}, 0.226{[}preterm{]}, 0.101
{[}postdatism{]} and 0.377 {[}NICU admission{]}, hence implying a
stronger positive correlation of SFT with adverse maternal outcomes. The
p values were lower for correlation of SFT suggesting greater
statistical significance. This paralleled with the study done by Suresh
A et al , which substantiated that SFT was a better predictor than BMI
for adverse maternal outcomes\textsuperscript{15}.

\textbf{CONCLUSION}

We could draw a positive correlation between SFT and BMI hence
establishing SFT was a maker of obesity.BMI showed a positive
correlation with adverse pregnancy outcomes in mother as well as fetus,
but SFT showed stronger and more statistically significant correlation
for the same. Thus, we could rightly infer that SFT is a better
independent predictor of obesity related adverse pregnancy outcomes.
This opens huge possibilities for employing SFT as a surrogate marker
for visceral obesity.Hence SFT can be used as a reliable, reproducible,
and objective marker for obesity related risk modeling in pregnancies in
the future.

\textbf{DISCLOSURE OF INTERESTS}

I hereby declare that to the best of my knowledge, the authors have no
relevant conflicts of interests\textbf{.}The submitted research paper
does not violate the copyright act in any way, is free of plagiarism,
and the ``questionnaires'' or ``scores'' being used are copyright-free
(or that the necessary permission has been obtained from the copyright
holders).

\textbf{CONTRIBUTION TO AUTHORSHIP}

Author Nila Surendran is the corresponding author and has made the
substantial the proConception of the idea and design of study was
contributed by author Prathiksha Gupta who also guided the study while
being performed. Author Nila Surendran drafted the manuscript and was
assisted by Authors Utkarsha Aggarwal and Pallavi Shekhawat for critical
revision and proof reading. All the authors have made contribution to
the final manuscript.

\textbf{FUNDING}

No funding was received.

\textbf{CONSENT OF PATIENTS}

At the outset the study participants were briefed about the nature of
study and the procedures involved. If they were willing to proceed then
a fully informed, written consent in the regional language, with date
was obtained from each one of them before conducting the study.

\textbf{ETHICS APPROVAL}

This study protocol with Reg No. ESIPGIMSR-IEC/2018050 was reviewd and
approved by the institutional ethical committee , IEC-ESI PGIMSR New
Delhi on 29/12/2018.

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\end{enumerate}

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