Aminotic Fluid Index and its Correlation with Fetal Growth and Perinatal Outcome

Abstract

The present study aimed to measure amniotic fluid index (AFI) in high-risk pregnancies at ≥30 weeks of gestation and its correlation with fetal growth and perinatal outcome. The Study was carried out in the Department of Obstetrics and Gynecology Hindu Rao Hospital, Delhi. Ultrasound examination was done on women with high-risk pregnancy (pregnancy-induced hypertension, intrauterine growth restriction, diabetes, and postdated pregnancy etc.) attending the antenatal OPD and maternity ward at ≥30 weeks of gestation. AFI was measured by the four quadrant technique. The study included 48 (48 %) primigravida and 52 (52 %) multigravida. Sixteen patients with a history of previous abortion had mean AFI of 9.97 cm which was lower than patients with no history of previous abortion i.e., 11.87 cm (P ≥ 0.1 insignificant). The mean AFI was maximum between 34–36 weeks, i.e., 13.1 cm, after which, it gradually decreased to 9.08 cm beyond 40 weeks. Mean AFI of patients with <40 weeks of gestation gradually decreased from 12.2 cm to 8.0 cm after 42 weeks (P value <0.05). Patients with IUGR had low mean AFI i.e., 9.8 cm whereas mean AFI in patients without IUGR was 12.1 cm (P value <0.01). Congenital anomalies were found in 4 % patients in the present study. Out of seven cases of perinatal mortality encountered, four (57 %) had abnormal AFI values, of which, two had low AFI (i.e., <8 cm) and two had abnormally-high AFI values i.e., >18 cm. Serious congenital malformations were present in three neonates, which resulted in early neonatal death. Out of these three, one patient had low AFI i.e., <8 cm and one had abnormally-high AFI value i.e., >24 cm. The study supports the view that AFI is a quick, noninvasive, and good indicator of fetal outcome in high-risk pregnancy.

Full text

ORIGINAL ARTICLE
Aminotic Fluid Index and its Correlation with Fetal Growth
and Perinatal Outcome
Sonia Madaan
1
•Suman Lata Mendiratta
1
•Pawan Kumar Jain
2
•
Meenakshi Mittal
1
Received: 25 March 2015 / Accepted: 29 July 2015 / Published online: 28 August 2015
ÓSociety of Fetal Medicine 2015
Abstract The present study aimed to measure amniotic
fluid index (AFI) in high-risk pregnancies at C30 weeks of
gestation and its correlation with fetal growth and perinatal
outcome. The Study was carried out in the Department of
Obstetrics and Gynecology Hindu Rao Hospital, Delhi.
Ultrasound examination was done on women with high-
risk pregnancy (pregnancy-induced hypertension,
intrauterine growth restriction, diabetes, and postdated
pregnancy etc.) attending the antenatal OPD and maternity
ward at C30 weeks of gestation. AFI was measured by the
four quadrant technique. The study included 48 (48 %)
primigravida and 52 (52 %) multigravida. Sixteen patients
with a history of previous abortion had mean AFI of
9.97 cm which was lower than patients with no history of
previous abortion i.e., 11.87 cm (P C0.1 insignificant).
The mean AFI was maximum between 34–36 weeks, i.e.,
13.1 cm, after which, it gradually decreased to 9.08 cm
beyond 40 weeks. Mean AFI of patients with \40 weeks
of gestation gradually decreased from 12.2 cm to 8.0 cm
after 42 weeks (P value \0.05). Patients with IUGR had
low mean AFI i.e., 9.8 cm whereas mean AFI in patients
without IUGR was 12.1 cm (P value \0.01). Congenital
anomalies were found in 4 % patients in the present study.
Out of seven cases of perinatal mortality encountered, four
(57 %) had abnormal AFI values, of which, two had low
AFI (i.e., \8 cm) and two had abnormally-high AFI values
i.e., [18 cm. Serious congenital malformations were pre-
sent in three neonates, which resulted in early neonatal
death. Out of these three, one patient had low AFI
i.e., \8 cm and one had abnormally-high AFI value
i.e., [24 cm. The study supports the view that AFI is a
quick, noninvasive, and good indicator of fetal outcome in
high-risk pregnancy.
Keywords Amniotic fluid index (AFI) 
Oligohdramnios Polyhdramnios IUGR Perinatal
outcome High-risk pregnancy
Introduction
Amniotic fluid acts as a protective layer which exerts a
cushion-like effect for the growing fetus against mechani-
cal and biological injury. Amniotic fluid may be regarded
as the largest part of the fetal extracellular space, and it
provides a more accessible means than fetal blood for
investigation of the fetus and its environment. Amniotic
fluid assessment is an integral part of the antenatal evalu-
ation of pregnancies at risk for an adverse pregnancy out-
come especially in the third trimester [1,2]. Detecting the
fetus at risk for in utero damage or death, quantifying, and
balancing the fetal risk against the risk of neonatal com-
plications from immaturity, and determining the optimal
time and mode of intervention are the cornerstone of
modern day obstetrics care and perinatal medicine [3].
Reduced amniotic fluid volume (AFV) is associated
with adverse effects such as meconium staining, congenital
anomalies, growth retardation, dysmaturity, and fetal
asphyxia [4–6]. Polyhydramnios is sometimes associated
with major fetal anomalies [5], aneuploidy, macrosomia,
and stillbirth [6]. Decreased AFV in those pregnancies
&Suman Lata Mendiratta
sumanmendi@yahoo.co.in
1
Obstetrics & Gynaecology Department, North DMC Medical
College & Hindu Rao Hospital, A-3/224, Janakpuri,
New Delhi 110058, India
2
Radiology Department, North DMC Medical College &
Hindu Rao Hospital, New Delhi, India
123
J. Fetal Med. (June 2015) 2:61–67
DOI 10.1007/s40556-015-0049-8
Article published online: 2023-05-08

without premature rupture of the membranes can reflect a
fetus in chronic stress, shunting of blood to its brain,
adrenal and heart and away from other organs, which
include the kidney, and results in decreased fetal renal
perfusion and urinary output. Phelan et al. [7] have rec-
ommended that labor induction be considered in patients
with oligohydramnios (AFI \5 cm) to reduce the
increased risk of fetal death and morbidity. An antepartum
amniotic fluid index (AFI) of 5 cm or less is a predictor of
adverse perinatal outcome in terms of meconium staining,
cesarean section for fetal distress, birth weight, low Apgar
scores and cord pH [8]. AFI of [18 cm is taken as cut-off
point for normal limit of AFI. Pregnancy complicated with
polyhydramnios is also classified as high risk. AFV can be
measured by dye-dilution techniques and by direct quan-
tification at the time of cesarean delivery, but both methods
are invasive, require laboratory support, and when mea-
sured at the time of operative abdominal delivery, cannot
be used serially to evaluate high-risk pregnancies [1]. The
limitation of the direct AFV measurement led to the use of
ultrasonic AFV estimation. Ultrasonography is noninvasive
and can clinically quantitate the AFV. There are various
reported ultrasonographic modalities to assess AFV like (1)
single deepest pocket (2) 2-diameter pocket, and (3) AFI by
4-quadrant method. Since the introduction of AFI by
Phelan et al. [7], a rapid semi-quantitative assessment of
AFV can be performed quickly, is easily taught, and is
reproducible.
AFI also facilitated the diagnosis of a congenital
anomaly not detected in referring clinics. The antepartum
information regarding malformation was valuable for the
patients and their health-care providers in deciding on the
timing and mode of delivery, determining an etiology of
intrauterine or postnatal death, and counseling of future
pregnancies. The present study was aimed to measure AFI
in high-risk pregnancies C30 weeks of gestation and its
correlation with fetal outcome.
Materials and Methods
This was a one year prospective study undertaken in the
department of Obstetrics and Gynecology, Hindu Rao
Hospital, Delhi a period of one year, after obtaining
ethical clearance from institutional committee. Ultra-
sound examination was done on women with high-risk
pregnancy (pregnancy-induced hypertension, intrauterine
growth restriction, diabetes, and postdated pregnancy
etc.) attending the antenatal OPD and maternity ward
at C30 weeks of gestation. Only patients who were sure
of dates were included in the study. Patients with pre-
mature rupture of membranes and twin pregnancy were
excluded from the study.
A detailed history was taken and a general physical and
obstetrics examination were done. The patient was then
subjected to ultrasonographic examination. Routine scan
for fetal well being was done and AFI was measured by the
4-quadrant technique [7]. The vertical diameter of the
maximum pocket was measured in centimeters in each of
the four quadrants and measurement obtained from each
quadrants were summed to form the AFI in centime-
ters.Follow-up of these patients was done till delivery and
their neonatal outcome was noted in terms of fetal distress
in labor, birth weight, Apgar at five minutes, congenital
anomalies, and perinatal mortality. The results were com-
piled and analyzed.
Results
The present study was conducted on 100 antenatal patients
over a period of one year. All the 100 patients included in
the study had attended antenatal OPD/maternity ward at
Hindu Rao Hospital and delivered at the Labor Room in
Hindu Rao Hospital and the results were analyzed as
follows.
The majority of cases i.e., 62 (62 %) were in the age
group of 21–25 years, followed by 27 (27 %) in the age
group 26–30 years, and the least were among the age
group [31 years (2 %). The mean age for the entire study
population was 24.31 years. The mean AFI for all age
groups was 11.567 ±5.364 cm. Present study included 48
(48 %) primigravida and 52 (52 %) multigravida.
The maximum cases i.e., 36 (36 %) had a gestational
age between 36 to 38 weeks at the time of enrollment. The
mean AFI was maximum, between 34–36 weeks i.e.,
13.1 cm, after which, it gradually decreased to 9.08 cm
beyond 40 weeks (Table 1). Mean AFI of patients
with \40 weeks of gestation gradually decreased from
12.2 cm to 8.0 cm after 42 weeks (P value \0.05) implies
significant relationship between post-term pregnancy and
AFI.
Antenatal complications in the present study group show
that anemia (Hb \10 g %) was the commonest compli-
cation found in 27 % cases, followed by IUGR (24 %),
PIH (20 %), previous abortions (16 %) cases, previous
lower segment cesarean section (11 %), oligohydramnios
(8 %), post-term pregnancy (6 %), and polyhydramnios
(5 %) being the next common complications (Table 2).
Mean AFI of patients with IUGR was 9.8 cm whereas
that in patients without IUGR was 12.1 cm, implies a
highly-significant relationship between IUGR and AFI. It
was found that out of 20 patients who were hypertensive, 8
(40 %) had low AFI i.e., \8 cm. The mean AFI of
hypertensive patients was 10.7 cm which was not signifi-
cantly different, statistically, from mean AFI of
62 J. Fetal Med. (June 2015) 2:61–67
123

normotensive patients i.e., 11.7 cm. The mean AFI in
patients with anemia was 11.63 cm which was not signif-
icantly different from patients without anemia i.e.,
11.54 cm. There was no disparity between AFI in preg-
nancies with previous LSCS and non-LSCS group, mean
AFI being 11.864 and 11.530 in cases and controls,
respectively. Mean AFI of patients \40 weeks gradually
decreased from 12.2 cm to 9.085 cm at [40 weeks and
8.0 cm after 42 weeks. There is no significant relation
between diabetes mellitus and AFI, though mean AFI in
pregnancies with diabetes (12.3 cm) was found to be more
than those without diabetes (11.5 cm). Mean AFI in Rh-
negative pregnancies was 12.8 cm which was slightly
higher than rest of the cases i.e., 11.5 cm. The mean AFI of
16 patients with a history of previous abortion was 9.97 cm
which was lower than those with no history of previous
abortions i.e., 11.87 cm.
Table 3depicts the relation of clinical assessment of
liquor to the AFI obtained ultrasonographically. Mean AFI
of 65 patients with clinically-normal liquor was 11.9 cm;
mean AFI of 27 patients with clinically-less liquor was
6.7 cm and mean AFI of eight cases with clinically-more
liquor was 24.3 cm. Statistical tests were applied and it was
found that clinical estimation of liquor has a sensitivity of
74.35 % and a specificity of 90.16 %, the accuracy being
84 %. Table 4depicts AFI in relation to delivery outcomes.
Discussion
The present study was undertaken to measure AFI in high-
risk pregnancies and to correlate it with fetal outcome. The
mean maternal age in this study was 24.31 ±3.19 years.
Magann et al. [9,10] in 1999 and 1997 reported the mean
Table 1 Distribution of
patients according to gestation
age at enrollment
POG at enrollment (weeks) No. of patients Mean AFI (cm) SD
30–32 1 4.000 –
32–34 4 9.200 1.860
34–36 15 13.133 7.067
36–38 36 12.908 5.602
38–40 24 11.354 4.977
[40 20 9.085 2.948
Total 100 11.567 5.364
AFI amniotic fluid index, POG period of gestation, SD standard deviation
Table 2 AFI in various high-risk pregnancy groups (some cases had more than one high-risk factor)
High-risk pregnancy factor No. of cases (out of 100) Mean AFI (cm) in cases Mean AFI (cm) in controls SD
IUGR 24 9.821 12.118 5.650
Hypertension 20 10.740 11.774 4.859
Anemia 27 11.637 11.541 2.690
Previous LSCS 11 11.864 11.530 6.581
Post-term [40 wks 20 9.085 12.188 2.948
Diabetes 5 12.300 11.528 5.709
Rh-negative 5 12.840 11.500 2.806
Previous abortions 16 9.97 11.870 2.617
AFI amniotic fluid index, IUGR intrauterine growth restriction, LCSC lower segment cesarean section, SD standard deviation
Table 3 Comparison of AFI
and clinical assessment of liquor
(by palpation)
Clinical assessment of liquor No. of cases % Mean AFI SD
Normal 65 65 11.975 3.417
Less 27 27 6.785 1.789
More 8 8 24.388 3.272
Total 100 100 11.567 5.364
PB0.001 (very highly significant)
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123

Table 4 AFI in relation to delivery outcomes
Mode of delivery in relation to AFI
a
Mode of delivery No. of cases % Mean AFI (cm) SD
Normal 63 63 12.162 4.999
Forceps 8 8 9.663 5.808
Cesarean 29 29 10.800 5.959
Total 100 100 11.567 5.364
Labor (spontaneous or induced) in relation to AFI
b
Labor No. of cases % Mean AFI SD
Spontaneous 54 98.35 11.976 4.385
Induced 25 31.64 11.024 6.255
Total 79 100 11.675 5.030
AFI in relation to meconium staining of liquor
c
Meconium staining of liquor No. of cases % Mean AFI SD
Absent 85 85 11.754 5.020
Present 15 15 10.507 7.131
Total 100 100 11.567 5.364
Relation of AFI with fetal heart rate
d
FHR No. of cases % Mean AFI SD
Normal 84 84 11.429 4.841
Bradycardia 12 12 11.975 7.507
Tachycardia 4 4 13.250 9.465
Total 100 100 11.567 5.364
AFI and its relation to birth weight
e
Birth weight (g) N % Mean AFI SD
\2000 17 17 7.976 2.467
2001–2500 27 27 12.448 6.526
2501–3000 43 43 12.247 4.106
[3000 13 13 12.185 7.476
Total 100 100 11.567 5.364
Apgar (5 min) versus AFI
f
Apgar N % Mean AFI SD
\9 10 10 11.550 8.448
9–10 90 90 11.569 4.976
Total 100 100 11.567 5.364
Congenital anomalies in the study group
g
Congenital anomaly Number AFI (cm)
Bilateral CTEV 1 6.3
Osteogenetis imperfecta 1 7.0
Fetal ascites ?treacheoesophageal interval ?laryngeal stenosis 1 26.0
Tracheoesophageal fistula ?anal agenesis 1 10.0
64 J. Fetal Med. (June 2015) 2:61–67
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maternal age of 24.8 ±5.3 and 24.5 ±0.5 years, respec-
tively, which was comparative to our study. In our study
parity has no relation to the distribution of cases as was
seen in the study conducted by Magann et al. [10].
In our study anemia was the commonest complication,
seen in 27 (27 %). Other significant complications were
IUGR (24 %), PIH (20 %), previous LSCS (11 %), oligo-
hydramnios (8 %), post-term pregnancy (6 %), and poly-
hydramnios (5 %). Magann et al. [11] reported IUGR in
4.74 %, PIH 3.16 %, and post-term pregnancy in 24.65 %
patients. Golan et al. [12] reported IUGR in 24.5 % and
hypertension in 22.1 %. In our study, among 27 % cases
that had anemia, no correlation was found between anemia
and AFI.
In our study, out of 29 patients with AFI \8 cm, 12
(41.4 %) patients had IUGR. O’Brien et al. [13] concluded
that fetal growth retardation is significantly associated with
an AFI of 7 cm, or less (P B0.001).
In the present study, 20 (20 %) patients were hyper-
tensive. Out of these patients, eight (40 %) had low AFI
scores (\8 cm). In a study conducted by O’Brien et al.
[13], out of 14 patients of mild PIH, only two patients i.e.,
14 % had a low AFI score (B7 cm). In a study by Magann
et al. [14] on patients with AFI \5 cm, 7.16 % patients
were found to be hypertensive.
In this study, out of six patients with post-term preg-
nancy, oligohydramnios (AFI \5 cm) was seen in 2
(33.3 %) cases. In a study conducted by Marks and Divon
[14] on post-term pregnancy, oligohydramnios was
demonstrated in 59 (11.5 %) patients. If diabetes is asso-
ciated with macrosomia and neural tube defects, polyhy-
dramnios may develop. In our study, it was observed that
mean AFI of five patients with diabetes was more
(12.3 cm) than nondiabetic patients (11.5 cm) though it
was not statistically significant (P value C0.1).
In the present study, AFI according to gestational age
was studied. The mean AFI was 11.567 cm. Maximum AFI
of 13.13 cm (mean) was seen at 34–36 weeks of gestation,
which gradually decreased to 9.085 (mean) after 40 weeks.
Similarly, Phelan et al. [7] demonstrated a mean AFI of
12.9 ±4.6 in 353 pregnancies at the gestational age
ranging from 36–42 weeks. Bowen-Chatoor and Kulkarni
[15] demonstrated a mean AFI of 9.93 ±4.37 cm at
42 weeks, which is comparable to our study.
In our study, it was observed that mean AFI of five
patients with Rh-negative pregnancy was more i.e.,
12.84 cm than rest of patients i.e., 11.5 cm. Mean maternal
weight in our study was 64.87 ±9.66 kg, with majority of
cases between 50–65 kg. Fifty four (68.35 %) patients had
spontaneous onset of labor while 25 (31.64 %) were
induced. The main indication for induction was PIH, IUGR
followed by postdated pregnancy.
In this study, out of 29 patients with low AFI (\8 cm),
six (20.7 %) had forceps delivery, whereas 13 (44.8 %)
Table 4 continued
AFI versus perinatal mortality
h
Perinatal mortality AFI (cm)
\8 8–18 [18
Fresh stillbirth – – 1
Neonatal death 2 3 1
AFI amniotic fluid index, CTEV congenital talipes equinovarus, FHR fetal heart rate, SD standard deviation
a
Mean AFI in patients undergoing assisted delivery was found to be lower (9.66 cm in forceps and 10.8 cm in cesarean group) than mean AFI in
patients undergoing normal delivery (i.e., 12.16 cm). It was also found that among 28 patients who had low AFI, 6 patients (42 %) had forceps
delivery whereas 13 (46.42 %) had cesarean section
b
The commonest cause of induction of labor in the study group was PIH (32 %), IUGR (16 %) and post-dated pregnancy (12 %)
c
PC0.1. The mean value of AFI (10.5 cm) in patients with meconium staining of liquor was not significantly different from those without
meconium staining of liquor (11.7 cm). P C0.1 (not significant)
d
PB0.1 (not significant). There was no correlation between the FHR and AFI. Out of 28 patients with low AFI, six (21.42 %) had fetal
bradycardia and two (7.14 %) had fetal tachycardia
e
PB0.05 (significant relation). Mean AFI was found to be significantly lower (7.9 cm) in low birth weight group \2000 g (P value \0.05),
implies significant relation between birth weight and AFI
f
PC0.1 (not significant). Mean AFI in patients with APGAR \9 was not found to be significantly different from mean AFI in patients with
Apgar [9
g
Congenital anomalies were found in 4 % patients in our study. The salient feature noted was that three (75 %) out of these four cases had
abnormal AFI scores, two cases had low AFI scores (\8 cm) and one had high AFI value ([24 cm) while mean AFI of the remaining study
group was 11.54 cm
h
Out of seven cases of perinatal mortality encountered in our study, four (57 %) had abnormal AFI values, of which two had low AFI
(i.e., \8 cm) and two had abnormally-high AFI values (i.e., [18 cm). Three neonates had serious congenital malformations which resulted in
early neonatal death, of which one patient had low AFI (i.e., \8 cm) and one had abnormally-high AFI value (i.e., [24 cm)
J. Fetal Med. (June 2015) 2:61–67 65
123

patients had cesarean section. Out of 61 patients with
normal AFI, 47 (77 %) had normal delivery. According to
Rutherford et al. [16], incidence of cesarean section was
58 % in patients with AFI \8 cm which is slightly more
than our study. Their cesarean section rate in patients with
AFI [18 cm was 41 %, which was low (30 %) in our
study.
In our study, 15 cases had meconium-stained liquor, out
of which eight (53.33 %) had low AFI scores (B8 cm). In a
study by Golan et al. [12], a high incidence of meconium
staining of liquor (29.1 %) was seen in oligohydramnios. In
another study by Magann et al. [11], meconium-stained
amniotic fluid was seen in 13.8 % patients with
AFI B5 cm. In our study, out of eight patients with low
AFI (B5 cm), two (25 %) had fetal bradycardia. In a
similar study by Magann et al. [11], it was found that in
patients with AFI \5 cm, 24 % patients had fetal brady-
cardia, which was comparable to our study.
In our study, out of 29 patients with low AFI (B8 cm),
17 (58.62 %) had low birth weight babies (B2500 g). In 10
patients with AFI [18 cm, five (50 %) had low birth
weight babies. Martinez-Frias et al. [17] also observed
similar results in their study. According to Chauhan et al.
[18], AFI of \5 cm is associated with an increased risk of
low (\7) Apgar score.
In our study, four patients had babies with congenital
anomalies, out of which, two (50 %) had low AFI \8cm
and one had AFI [18 cm. In the study conducted by
Martinez- Frias et al. [17] on malformed newborns, 3.01 %
had oligohydramnios. Renal anomalies and lung defects
were associated with oligohydramnios. They reported
polyhydramnios in 3.69 % cases in their study. Esophageal
and gastrointestinal anomalies, neural tube defects, and
other central nervous system malformations were associ-
ated with polyhydramnios. In our study, osteogenesis
imperfecta and bilateral CTEV were associated with low
AFI of \8 cm, and tracheoesophageal fistula was associ-
ated with AFI [18 cm.
In our study perinatal mortality rate was 7 %. Of these
seven cases, three babies (42.85 %) had serious congenital
malformations, two cases (28.57 %) had low AFI
of \8 cm and two cases (28.57 %) had AFI [18 cm.
Biggio et al. [19] reported 6 % perinatal mortality in their
study of 370 women, which was comparable to our study.
Conclusion
Amniotic fluid provides a more accessible means than fetal
blood for surveillance of the fetus and its environment.
Amniotic fluid assessment is an integral part of the ante-
natal evaluation of pregnancies at risk for an adverse
pregnancy outcome. Our study supports the view that AFI
is a quick, noninvasive and good indicator of fetal outcome
in high-risk pregnancy.
Funding None.
Compliance with Ethical Standards
Conflict of interest None.
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