Available via license: CC BY-NC
Content may be subject to copyright.
December 2020 · Volume 9 · Issue 12 Page 5060
International Journal of Reproduction, Contraception, Obstetrics and Gynecology
Sengodan SS et al. Int J Reprod Contracept Obstet Gynecol. 2020 Dec;9(12):5060-5064
www.ijrcog.org
pISSN 2320-1770 | eISSN 2320-1789
Original Research Article
Amniotic fluid optical density at spontaneous onset of labour and
it’s correlation with gestational age, birth weight and
functional maturity of newborn
Subha S. Sengodan*, Santhya Velumani
INTRODUCTION
Respiratory distress syndrome remains a common cause
of neonatal morbidity and mortality. The pulmonary
system is among the last of the fetal organ system to
mature both functionally and structurally.
Pulmonary surfactant increases the lung compliance and
prevents the collapse of alveoli during expiration.
Biochemical analysis of LS ratio of 2:1 and phosphatidyl
glycerol indicates pulmonary maturity.1,2 Among the
biophysical methods, bubble formation tests, optical
density at 650 nm, flourescense polarisation lamellar
body concentration helps in determining the fetal lung
maturity.2-6
Gestational age at delivery is unique to fetomaternal
unit.7 One of the most important preventive measures in
obstetrics is the individual evaluation of most appropriate
time to terminate the pregnancy.8 It is a conventional
degree that babies born between 37-40 weeks are
completely mature. Even after 40 weeks full term, an
evidence of 0.25% RDS has been recorded. About 0.05%
who were delivered electively between 37-40 weeks
ABSTRACT
Background: Respiratory distress is the common cause of neonatal morbidity and mortality. Babies born even at 40
weeks of gestation developed respiratory distress. The maturity of newborn is independent of gestational age and birth
weight of newborn. In this study amniotic fluid optical density (AFOD) is correlated with the functional maturity of
newborn.
Methods: In this study, hundred singleton pregnant women who underwent first trimester scan and crown rump
length estimation, and who were on spontaneous labor were selected for this observational study. Under aseptic
precautions AF samples were collected while doing amniotomy with 2 ml disposable syringe, also collected during
caesarean section after careful hysterotomy from the bulging membranes. Amniotic fluid optical density studied with
spectrometer at 650 nm. Birth weights were recorded for all the babies. Babies are also looked for the respiratory
distress, NICU admission.
Results: In this study, respiratory distress was reported in 28% of newborns whereas 72% of newborns did not have
distress. In the present study, 27% of newborns were admitted in NICU where as 73% of the newborns were on
mother’s side following delivery. Babies with AFOD 0.98±0.27 were functionally mature, skin was pleased brown in
colour with little vernix, none of them had respiratory distress. Amniotic fluid optical density <0.4 developed
respiratory distress.
Conclusions: Amniotic fluid optical density is a simple method to assess the functional maturity of newborn.
Keywords: AFOD, Functional maturity, Respiratory distress
Department of Obstetrics and Gynecology, Government Kumarmangalam, Medical College Hospital, Salem, Tamil
Nadu, India
Received: 29 September 2020
Revised: 05 November 2020
Accepted: 06 November 2020
*Correspondence:
Dr. Subha S. Sengodan,
E-mail: drppsamysubha@gmail.com
Copyright: © the author(s), publisher and licensee Medip Academy. This is an open-access article distributed under
the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial
use, distribution, and reproduction in any medium, provided the original work is properly cited.
DOI: https://dx.doi.org/10.18203/2320-1770.ijrcog20205247
Sengodan SS et al. Int J Reprod Contracept Obstet Gynecol. 2020 Dec;9(12):5060-5064
International Journal of Reproduction, Contraception, Obstetrics and Gynecology Volume 9 · Issue 12 Page 5061
required mechanical ventilation.9 The lung skin
interaction by the surfactant causes vernix detachment,
increases amniotic fluid turbidity.10,11
Though there are several techniques practiced in recent
times to assess the maturity of fetus, role of amniotic
fluid optical density (AFOD) in assessing the gestational
age and functional maturity of newborn has been reported
in several researches.12-14 Amniotic fluid absorbance at
650 nm is considered as a standard investigation for lung
maturity evaluation.15 Even the low birth weight babies if
functionally mature can be managed at home.16 In our
study we confirm this phenomenon in terms of AFOD
which measures lung maturity, skin maturity as well as
biological age. Hence this study was conducted to
correlate the AFOD at spontaneous onset of labour with
gestational age, birth weight and functional maturity of
newborn.
Aims and objectives
To establish the correlation between amniotic fluid
optical density (AFOD) with gestational age, birth weight
and functional maturity of newborns and to study the
functional maturity of the newborns, especially in terms
of lung maturity by means of presence or absence of
respiratory distress in babies born out of spontaneous
labour.
METHODS
A prospective study conducted on hundred antenatal
women, admitted for delivery in GMKMCH, Salem.
Duration of study:
July 2019 to December 2019.
Ethical committee approval
Ethical committee approval was obtained for this study to
find the correlation between amniotic fluid optical
density with gestational age, birth weight and functional
maturity of the new born among antenatal mothers
attending inpatient department of Obstetrical and
Gynecology, from the ethics committee.
Inclusion criteria
Women who underwent first trimester scan and crown
rump length estimation and women with regular
menstrual cycles who underwent USG at less than 20
weeks gestation which is in agreement with the gestation
age calculated from the last menstrual period.
Exclusion criteria
Blood stained and meconium stained amniotic fluid
samples, intrauterine growth restriction, premature
rupture of membranes, multiple pregnancies.
Under aseptic precautions, amniotic fluid samples were
collected while doing amniotomy with a sterile syringe.
Amniotic fluid samples were also collected at cesarean
section, after careful incision in the uterus from the
bulging membranes. Minimum 2 ml of amniotic fluid
transferred to the plain test tube. Amniotic fluid optical
density (AFOD) was measured using spectrometer. The
wavelength was set at 650 nm, first the control test tube
with water was read by the spectrometer followed by the
amniotic fluid sample. The amniotic fluid optical density
(AFOD) was shown immediately as digital number in the
spectrometer.
Figure 1: Spectrometer with test tube containing
amniotic fluid.
Figure 2: AFOD levels and fetal maturity.
Birth weights were recorded for all the babies by
electronic weighing machine. APGAR scores at one
minute and 5 minute were obtained. Babies were
observed for clinical signs of respiratory distress. Clinical
signs of respiratory distress (RR>60, grunting, retraction
of ribs/sternum, low SPO2 requiring O2 for more than 2
hours (to exclude transient tachypnea of newborn), chest
x-ray findings after 24 hours were suggestive of RDS.
Factors like sepsis, gestational diabetes mellitus,
pneumonia, meconium aspiration, congenital anomalies
were excluded.
Sengodan SS et al. Int J Reprod Contracept Obstet Gynecol. 2020 Dec;9(12):5060-5064
International Journal of Reproduction, Contraception, Obstetrics and Gynecology Volume 9 · Issue 12 Page 5062
Data analysis
The data was entered in excel sheet and analyzed using
statistical package for social sciences (SPSS- version 17).
Descriptive statistics with mean, standard deviation (SD)
and proportions (%) were calculated for continuous
variables. To test the hypothesis chi Square test,
independent sample t test and ANOVA were used
appropriately. P value <0.05 was considered as
statistically significant.
RESULTS
In this study, there were hundred participants included.
Among them majority (47%) of them were in the age
group of 21-25 years followed by 26-30 years (33%), less
than or equal to 20 years (15%) and 31-35 years (5%).
Table 1: Proportion of participants in different
gestational age.
Gestational age
Percentage
33-33 weeks + 6 days
5.0
34-34 weeks + 6 days
11.0
35-35 weeks + 6 days
5.0
36-36 weeks + 6 days
26.0
37-37 weeks + 6 days
20.0
38-38 weeks + 6 days
23.0
39-39 weeks + 6 days
5.0
40-40 weeks + 6 days
5.0
Spontaneous labour occurred most commonly in the
gestational age group 36-36 weeks + 6 days of gestation
(26%) followed by 38-38 weeks + 6 days of gestation
(23%), 37-37 weeks + 6 days of gestation (20%) and 34-
34 weeks + 6 days of gestation (11%). Also 5% of cases
had spontaneous labour in the gestational age group 33-
33 weeks + 6 days, 35-35 weeks + 6 days, 39-39 weeks +
6 days of gestation and 40-40 weeks + 6 days of
gestational age. In this study, respiratory distress was
reported in 28% of newborns whereas 72% of newborns
did not have distress.
Table 2: Association between gestational age and
respiratory distress.
Gestational age
(in weeks)
Respiratory distress
P value
Present
Absent
33-33+6 days
5
0
0.000*
34-34+6 days
6
5
35-35+6 days
3
2
36-36+6 days
3
23
37-37+6 days
2
18
38-38+6 days
7
16
39-39+6 days
0
5
40-40+6 days
2
3
Total
28
72
Table 3: Difference in mean AFOD with respect to
respiratory distress.
Variable
Respiratory
distress
Mean±SD
P value
Amniotic fluid
optical density
Present
0.4±0.1
0.000*
Absent
1.2±0.1
*Significant
Mean difference in AFOD among the cases with and
without respiratory distress was found to be 0.4±0.1 and
1.2±0.1, respectively. The difference in AFOD with
respect to respiratory distress was found to be statistically
significant in this study with a p value of 0.000.
Figure 3: Correlation between gestational age
and AFOD.
DISCUSSION
Gestational age by itself does not always exclude the
possibility of respiratory distress syndrome because
literature has reported prevalence of RDS after 40 weeks
of gestation as 0.25%.17,18 Though the percentage is
small, the number increases to significant proportions
when extrapolated to larger populations which are
avoidable. American College of Obstetricians and
Gynecologists guidelines recommend the obstetricians to
confirm fetal pulmonary maturity prior to elective
delivery less than 39 weeks gestation.19 ACOG
recommends the AFOD value >0.15 of a centrifuged
amniotic fluid sample to confirm lung maturity. The
onset of spontaneous labour takes place at AFOD value
around 0.98.21
In this study, we observed that newborns with AFOD
value <0.40 developed RDS. The findings are in
accordance with the previous studies, AFOD represents
indirectly the amount of surfactant.21,22 Hence severity
depends on the how low the AFOD value is or in other
words how low the surfactant phospholipids are and not
always how low the chronological age is. There could be
other factors accounting for less severity of RDS like trial
of labour or unknown constitutional factors at advanced
gestational age despite low surfactant levels as revealed
by low AFOD values.23 However the severity could be
Sengodan SS et al. Int J Reprod Contracept Obstet Gynecol. 2020 Dec;9(12):5060-5064
International Journal of Reproduction, Contraception, Obstetrics and Gynecology Volume 9 · Issue 12 Page 5063
more than expected on rare occasions.24-26 Exact
measurements of AFOD is possible in AFI value of 9-
16.27 Ram et al reported mean optical density of
1.03±0.31 in babies devoid of RDS.28,29 Babies With
AFOD 0.98±0.27 are functionally mature, skin was
pleased brown in colour with little vernix, none of them
had respiratory distress.30 Amniotic fluid optical density
<0.4 developed respiratory distress.31,32
In our study, mean difference in AFOD among the cases
with and without respiratory distress was found to be
0.4±0.1 and 1.2±0.1, respectively. The difference in
AFOD with respect to respiratory distress was found to
be statistically significant in this study. In this study, it
was found that amniotic fluid optical density levels were
high among the newborns with better APGAR score at
five minutes. Thus shows a significant positive
correlation between APGAR at five minutes and amniotic
fluid optical density.
The onset of labour is more closely related to fetal
functional maturity than either gestational age or birth
weight.33 The gestational age at delivery is unique to each
feto-maternal unit . The understanding of AFOD prevents
iatrogenic prematurity and complications of postmaturity
thereby optimizing labour.
Limitation of this study is only 100 amniotic fluid
samples are studied, further studies are needed.
CONCLUSION
In this study we conclude that each fetus has got its own
maturity potential amniotic fluid optical density (AFOD)
was found to be significantly associated with functional
maturity of newborn. It was found that AFOD increases
with gestational age.
AFOD is higher among the newborns with better APGAR
score. In our study babies with AFOD <0.40 developed
respiratory distress irrespective of gestational age and
birth weight of newborn. Babies with AFOD 1.2±0.1 are
functionally mature and did not develop respiratory
distress irrespective of gestational age and birth weight of
newborn, which is found to be statistically significant.
Induction of labour needs to be reviewed in lights of
AFOD which determines the preparedness of labour and
hence the biological gestational age that is more relevant
than the estimated date of confinement (EDC).
Funding: No funding sources
Conflict of interest: None declared
Ethical approval: The study was approved by the
Institutional Ethics Committee
REFERENCES
1. Tsao FH, Zachman RD. Use of quantitative amniotic
fluid phosphatidylglycerol as a criterion for fetal
lung maturation. Am J Perinatol. 1992 Jan;9(01):34-
7.
2. Dubin SB. The laboratory assessment of fetal lung
maturity. Am J Clin Pathol. 1992;97(6):836-49.
3. Hagen ED, Link JC, Arias FE. A comparison of the
accuracy of the TDx-FLM assay, lecithin-
sphingomyelin ratio, and phosphatidylglycerol in the
prediction of neonatal respiratory distress syndrome.
Obstet Gynecol. 1993;82(6):1004-8.
4. Ruch AT, Lenke RR, Ashwood ER. Assessment of
fetal lung maturity by fluorescence polarization in
high-risk pregnancies. J Reprodu Med.
1993;38(2):133-6.
5. Fakhoury G, Daikoku NH, Benser J, Dubin NH.
Lamellar body concentrations and the prediction of
fetal pulmonary maturity. Am J Obstet Gynecol.
1994;170(1):72-6.
6. Salmona M, Diomede L, Moro G, Minoli I, Bernini
S, Agosti S. Fetal lung maturity evaluation with
fluorescence polarization of the amniotic fluid. Jo
Perinat Med. 1993;21(5):349-54.
7. Popkin DR, Peddlr LJ. Women’s Health Today-
Perspectives on current research and Clinical
Practice: The proceedings of XIV World congress of
Obstetrics and Gynecology. In: Impact of Imaging in
Obstetrics and Gynecology- Prediction of birthdate
and newborns state. 1st edn. New York: Parthenon
publishing Group; 1994:246.
8. Morrison JJ, Rennie JM, Milton PJ. Neonatal
respiratory morbidity and mode of delivery at term:
influence of timing of elective caesarean section. Br
J Obstet Gynaecol. 1995;102:101-6.
9. Wax JR, Herson V, Carignan E, Mather J, Ingardia
CJ. Contribution of elective delivery to severe
respiratory distress at term. Am J Perinatol.
2002;19(2):81-6.
10. Narendran V, Randall WR, William LP, Steven BH.
Interaction between pulmonary surfactant and
vernix: a potential mechanism for induction of
amniotic fluid turbidity. J Pediatr Res. 2000;48:120-
4.
11. Klimek R. A new score for postnatal clinical
assessment of fetal maturity in newborn infants. Int J
Gynecol Obstet. 2000;71:101-5.
12. Bhatnagar PK. Study of low birth weight neonates.
Med J Armed Forces India. 2000;56:293-5.
13. Klimek R. The use in obstetrics of quantum theory as
well as modern technology to decrease the morbidity
and mortality of newborns and mothers during
iatrogenic induced delivery. Neuroendocrinol
Letters. 2001;22:5-8.
14. Zanardo V, Simbi AK, Franzoi M, Solda G,
Salvadori A, Trevisanuto D. neonatal respiratory
morbidity risk and mode of delivery at term:
influence of timing of elective caesarean delivery.
Acta Paediatr. 2004;93:643-7.
15. Cunningham G, Leveno KJ, Bloom SL, Hauth JC,
Gilstrap LC, Wenstorm KD. Diseases and injuries of
Fetus and New born. In: Willaims Text book of
Sengodan SS et al. Int J Reprod Contracept Obstet Gynecol. 2020 Dec;9(12):5060-5064
International Journal of Reproduction, Contraception, Obstetrics and Gynecology Volume 9 · Issue 12 Page 5064
Obstetrics. 22nd edn. New York: McGraw-Hill
Medical Publishing Division; 2005:367.
16. Park K. Child Survival and Safe Motherhood
Programme (CSSM). In: Park’s Text book of
Preventive and Social Medicine. 18th edn. Jabalpur:
Banarasidas Bhanot Publishers; 2005:344.
17. Abbas M, Bakr A. Severe respiratory distress in
Term infants born electively at high altitude. BMC
Pregnancy Childbirth. 2006;6:1-4.
18. Peter S, Rhiannon W, Ian R. Antenatal
betamethasone and incidence of neonatal respiratory
distress after elective caesarean section: (ASTECS)
pragmatic randomized trial. Obstet Gynecol Survey.
2006;61:157-8.
19. ACOG committee opinion no. 394. Cesarean
delivery on maternal request. Obstet Gynecol.
2007;11096:1501.
20. ACOG educational bulletin. ACOG Practice Bulletin
No. 97: Fetal Lung Maturity. Obstet Gynecol.
2008;112(3):717-26.
21. Luo G, Norwitz ER. Revisiting amniocentesis for
fetal lung maturity after 36 weeks’ gestation. Rev
Obstet Gynecol. 2008;1(2):67.
22. Ram S. Amniotic fluid optical density at spontaneous
onset of labor and its correlation with gestational
age, birth weight, functional maturity and vernix
caseosa of new born. Calicut Med J. 2009;7(4).
23. Kamath BD, Todd JK, Glazner JE, Lezotte D, Lynch
AM. Neonatal outcomes after elective cesarean
delivery. Obstet Gynecol. 2009;113(6):1231-8.
24. Tita ATN, Landon MB, Catherine Y, Lai SY,
Leveno, Varner MW, et al. Timing of elective repeat
cesarean delivery at term and neonatal outcomes. N
Engl J Med. 2009;360:112-20.
25. Raba G, Baran P. Obstetric outcomes in oxytocin-
related and spontaneous deliveries- analysis of 2198
cases. Ginekol Pol. 2009;80(7):508-11.
26. Al-Zirqi I, Vangen S, Forsén L, Stray-Pedersen B.
Effects of onset of labor and mode of delivery on
severe postpartum hemorrhage. Am J Obstet
Gynecol. 2009;201(3):273.e1-9.
27. Shankar R Sandya R. Role of echogenic amniotic
fluid particles and optical density in prediction of
RDS and labor. Internet J Med Update. 2010;5(1):3-
11.
28. Ram SH, Ram S. Role of echogenic amniotic fluid
particles and optical density in prediction of
respiratory distress syndrome and labor. Internet J
Med Update. 2010;5(1).
29. Samartha ram h, sandhya ram s, amniotic fluid
optical density (AFOD) surge coincides with the
onset of spontaneous term labor. Paper presented at
55th AICOG-2012.
30. Hanuman RK. Correlation between amniotic fluid
optical density (AFOD) and functional maturity
status of the newborn at caesarean delivery in GDM.
IOSR J Dent Med Sci. 2014;13(5V):12-6.
31. Ram SH, Ram SD. Individualized term for each
fetus: From surge in amniotic fluid optical density
(AFOD). Internet J Gynecol Obstet. 18(1):1-6.
32. Rao NYL, Isuapalli V, Samyukta Ila S. Amniotic
fluid optical density (AFOD) correlates with the lung
maturity as well as complete maturity of the fetus- a
clinical observational study. IAIM. 2015;2(8):30-7.
33. Ram HS, Samyuktha IS, Nagasree V. Outcomes of
induction of labor with mature and premature
amniotic fluid optical density (AFOD): a preliminary
case control study. Trop J Obstet Gynaecol.
2019;36(2):206-1.
Cite this article as: Sengodan SS, Velumani S.
Amniotic fluid optical density at spontaneous onset
of labour and it’s correlation with gestational age,
birth weight and functional maturity of newborn. Int
J Reprod Contracept Obstet Gynecol 2020;9:5060-4.
