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ORIGINAL ARTICLE
Year : 2022  |  Volume : 25  |  Issue : 6  |  Page : 938-943

Borderline amniotic fluid index in nigerian pregnant women is associated with worse fetal outcomes: Results of a prospective cohort study


1 Ipswich Hospital, East Suffolk and North Essex NHS, Foundation Trust, Suffolk, UK; Department of Obstetrics and Gynaecology, Delta State University Teaching Hospital, Delta State, Nigeria
2 Department of Obstetrics and Gynaecology, Delta State University Teaching Hospital, Warri, Delta State, Nigeria
3 Department of Radiology, Delta State University Teaching Hospital, Warri, Delta State, Nigeria
4 Department of Radiology, Central Hospital, Warri, Delta State, Nigeria

Date of Submission28-Nov-2021
Date of Acceptance31-Jan-2022
Date of Web Publication16-Jun-2022

Correspondence Address:
Dr. E O Aramabi
Department of Obstetrics and Gynaecology, Ipswich Hospital, East Suffolk and North Essex NHS Foundation Trust, Suffolk

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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njcp.njcp_1973_21

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   Abstract 


Background: The amniotic fluid index (AFI) is one of the parameters used to assess fetal well-being and predict perinatal outcomes. There is, however, a dearth of studies on the pregnancy outcomes of women with borderline AFI in Nigerian and African women. Aim: To compare the pregnancy outcomes of Nigerian women with borderline and normal amniotic fluid index. Subjects and Methods: This was a prospective cohort study conducted at two health facilities in Delta State, Southern Nigeria. A total of 114 pregnant women attending the antenatal clinics with singleton pregnancies at gestational age 37 to 41 + 6 weeks were recruited over a 5-month period. Fifty-seven subjects with borderline amniotic fluid index were matched with an equal number of subjects with the normal amniotic fluid index for gestational age, age of the parturient, and parity. These women were followed up till delivery, and pregnancy outcomes were determined. The data were analyzed using the Statistical Package for the Social Sciences (SPSS) version 22 software. Results: The results showed that borderline amniotic fluid index was associated with increased risk of adverse pregnancy outcomes including intrapartum fetal distress, Appearance, Pulse, Grimace, Activity, and Respiration (Apgar) score <7 in 5 min, and birthweight <2.5 kg, and these were statistically significant (P = 0.04, 0.01, and 0.04, respectively). Conclusions: Borderline AFI is associated with an increased risk of adverse pregnancy outcomes in low-risk Nigerian women.

Keywords: Amniotic fluid index, borderline, perinatal outcomes, pregnancy complications


How to cite this article:
Aramabi E O, Ebeigbe P N, Ogbeide A O, Onyemesili C J. Borderline amniotic fluid index in nigerian pregnant women is associated with worse fetal outcomes: Results of a prospective cohort study. Niger J Clin Pract 2022;25:938-43

How to cite this URL:
Aramabi E O, Ebeigbe P N, Ogbeide A O, Onyemesili C J. Borderline amniotic fluid index in nigerian pregnant women is associated with worse fetal outcomes: Results of a prospective cohort study. Niger J Clin Pract [serial online] 2022 [cited 2022 Jul 6];25:938-43. Available from: https://www.njcponline.com/text.asp?2022/25/6/938/347624




   Introduction Top


The amniotic fluid volume is one of the several parameters used to assess fetal well-being and perinatal outcomes.[1] It has been shown to be useful in predicting adverse outcomes such as fetal distress, meconium aspiration, cesarean delivery, and fetal mortality.[2],[3] One of the indices in assessing abnormalities in amniotic fluid volume (AFV) is the sonographic assessment of amniotic fluid index.[4],[5] Studies have revealed that AFI is an accurate criterion for estimating adequate placental function.[6] Amniotic fluid volume at any time is a balance between production and consumption and varies with gestational age.[7] Any decrease or increase in the volume of amniotic fluid may lead to pregnancy complications.[2]

Normal amniotic fluid volume has been defined in various ways. The 5th and 95th percentiles have been defined for AFI, single deepest pocket (SDP), the 2-diameter pocket, and dye-directed techniques across gestational ages as fluid levels have been found to vary significantly throughout pregnancy.[8] Nomograms for amniotic fluid in normal pregnancies have been developed by dye-determined methods, by AFI, dye-dilution and direct measurement, and sonographic estimate.[9]

In most studies, oligohydramnios has been defined as an AFI of 5 cm or less, and its associated maternal and fetal complications are proven.[10],[11] However, borderline AFI has been defined by different authors using different cut-offs. Phelan et al.[9] originally defined a borderline sonographic estimate of the amniotic fluid volume as an AFI of 5.1 cm to 8 cm, whereas Gumus et al.[11] and Banks et al.[12] in their studies on perinatal and pregnancy outcomes with borderline AFI used the range of 5.1cm–10 cm. This range was derived from a study by Miller and colleagues where an AFI range of 5.1–10 cm was found to be associated with pregnancies that resulted in stillbirths within the first 7 days of a normal modified biophysical profile.[13] Kreiser et al.[14] defined a borderline amniotic fluid volume as an AFI of greater than 5 cm but below the 2.5th percentile (based on gestational age-specific normative data of Moore and Cayle,[15] which would be an AFI of 6 cm to 9 cm.

The risks associated with a low AFI are well established, but less information is available regarding the clinical significance of a low-normal or borderline AFI. In most reported studies, the pregnancies with borderline AFI have shown outcomes such as nonreactive nonstress tests, fetal heart rate deceleration, meconium aspiration, immediate cesarean delivery, low Appearance, Pulse, Grimace, Activity, and Respiration (Apgar) score, low birth weight.

(LBW), neonatal intensive care unit (NICU) admission, and small for gestational age (SGA) in comparison with control subjects with normal amniotic fluid level (8.1–18 cm).[9],[16],[17],[18] Also, the low amniotic index may increase the operative delivery rate.[4] Banks and Miller also suggest that up to 16% of patients with a borderline AFI (5–8 cm) have the potential to progress to oligohydramnios within 4 days,[12] which has been shown to be associated with adverse fetal and neonatal outcomes.[18] Several studies have been conducted on borderline AFI and perinatal outcomes, but because they used different inclusion criteria, gestational ages, and definitions of borderline AFI, the results obtained are difficult to compare.[18]

Nigeria has a relatively high perinatal mortality rate with several factors contributing to this.[19],[20],[21] This study was conducted to assess the relationship between borderline AFI and adverse pregnancy outcomes while excluding those factors with a strong negative influence on pregnancy outcomes. Findings in this study will help to provide more information on the pregnancy outcomes of the borderline amniotic fluid index and its management and help to reduce the high perinatal morbidity and mortality rate in our setting if a positive relationship is established. Besides this, there is a dearth of studies on the pregnancy outcomes of women with borderline AFI in Nigerian and African women.

The vast majority of studies have been in Caucasian and Asian women, and there is a possibility that racial variations may exist. There is a need to add to the growing body of evidence on the association between borderline AFI and adverse pregnancy outcomes locally and globally in order to avail women with borderline AFI the full complement of appropriate risk management.


   Patients and Methods Top


This was a prospective cohort study which was performed at the Departments of Obstetrics and Gynecology and Radiology of Delta State University Teaching Hospital (DELSUTH), Oghara and Central Hospital, Warri between November 2016 and April 2017.

Ethical approval was obtained from the hospital research ethics committee of both hospitals. The patients were adequately counseled, and a written informed consent was obtained before any of the procedure was performed.

The study population consisted of consecutive cases of women with singleton, low-risk, intrauterine pregnancies. They had to be only women with well-established dates by standard obstetric criteria and intact membranes between the gestational age 37 weeks and 41 weeks and 6 days attending the antenatal clinics in both centers. Women whose dates could not be determined by standard obstetric criteria, with medical comorbidities, congenitally malformed fetuses, rupture of membranes, vaginal bleeding, and patients with multiple gestations were excluded from the study.

Pregnant women with normal amniotic fluid index were matched for age, gestational age, and parity with women with borderline amniotic fluid index. All patients were followed-up from recruitment, labor till delivery, and pregnancy and perinatal outcomes were recorded. The maximum time from measurement to delivery was 1 week. The patients who did not deliver within this duration were rescanned. Where a previously normal amniotic fluid index became borderline, such a patient was moved to the exposed group, and an appropriate unexposed patient was recruited.

Selected patients underwent an ultrasound scan for AFI estimation using the Toshiba Nemio XG ultrasound machine. The amniotic fluid volume was measured at the radiology department of both hospitals. The volume of amniotic fluid was quantified by the AFI four-quadrant technique as described by Moore and Cayle.[15] The uterine cavity was divided into four imaginary quadrants. The linea nigra was used to divide the uterus into the right and left halves. The umbilicus served as the dividing point for the upper and lower halves. With the use of linear-array, real-time B-scanning, and with a 3.75 MHz curved-linear transducer, the transducer was kept parallel to the patient's longitudinal axis and perpendicular to the floor. The diameter of the deepest, unobstructed, vertical pocket of fluid, free of the umbilical cord and fetal part was measured in each quadrant in centimeters. The amniotic fluid index is the sum of these four quadrants. Pockets confluent with pockets in adjacent quadrants were avoided. The value obtained for each patient was recorded on the patient's data collection proforma. During labor, continuous electronic fetal monitoring using the cardiotocograph was employed for patients who during the process of labor become high risk.


   Results Top


The study population consisted of 114 consecutive booked patients with singleton pregnancies between the gestational age of 37 weeks and 41 + 6 weeks attending the antenatal clinics at DELSUTH and Central Hospital, Warri.

The demographic characteristics are displayed in [Table 1]. The borderline AFI group had a bimodal age distribution [(25–29 years and 30–34 years (18, 31.6%)] compared to the normal AFI group [(25–29 years (24, 42.1%)]. Across the other age groups, there was a consistently higher number in the borderline AFI group. This difference was not statistically significant (P = 0.893). The majority of the parturients in the borderline (39, 68.4%) and normal AFI groups (38, 66.7%) were para 1–4. With respect to other variables such as gestational age at study entry and delivery, differences observed between the two groups were not statistically significant (P > 120 → 0.05).
Table 1: Demographic Characteristics of Patients

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With regard to the mode of delivery as seen in [Table 2], women in the borderline AFI group were consistently more likely to undergo induction of labor (P = 0.009, RR = 2.08, CI = 1.16–3.73), have assisted vaginal delivery (P = 123 0.006, RR = 3.00, CI = 1.29–7.00), antepartum caesarean delivery (P = 0.001, RR = 3.50, CI 1.53–8.20), and intrapartum caesarean section (P = 0.008, RR = 3.20, CI = 1.26–8.15). These differences were statistically significant (P < 0.05).
Table 2: Comparison of Mode of Delivery

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Intrapartum fetal distress (P = 0.035, RR = 2.29, CI = 1.02-8.13), Apgar score <7 in 5 min (P = 0.011, RR = 2.33, CI = 1.71–4.65) and birthweight <2.5 kg (P = 0.036) occurred more frequently in the borderline AFI group, this was statistically significant (P < 0.05). Meconium-stained liquor, neonatal intensive care unit admission >24 h, intrapartum fetal death, and early neonatal death also occurred more frequently in the borderline AFI group. However, this was not statistically significant (P > 0.05) [Table 3].
Table 3: Comparison of Perinatal Outcome Measures in Study Groups

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   Discussion Top


The results of this study showed that modes of delivery such as spontaneous labor, induction of labor, assisted vaginal delivery, antepartum cesarean section, and intrapartum cesarean section were statistically significantly higher in the borderline AFI group. Parturients with borderline AFI in this study were statistically significantly more likely to undergo the induction of labor. This corroborated findings from previous studies.[1],[11],[18] In this study, parturients with borderline AFI were thrice as likely to have assisted vaginal delivery (vacuum extraction or forceps delivery) compared to those with normal AFI. However, this is in contrast to other studies. Gumus et al.[11] found no association between borderline AFI and assisted vaginal delivery. The implication of the statistical significance of assisted vaginal delivery in women with borderline AFI is that there might be an increased need for obstetric personnel at the delivery of these women, increased incidence of birth trauma (both maternal and fetal), and increased neonatal intensive care services.

Similar to other studies,[17],[22],[23] parturients with borderline AFI in this study were more likely to undergo cesarean delivery when compared to their normal AFI counterparts. However, this was contradicted by other previous studies.[15],[24] Differences may be due to the fact that these studies were retrospective studies.

A major finding of this study was that women with borderline AFI had babies with a higher risk of intrapartum fetal distress, birthweight <2.5 kg, and Apgar <7 in 5 min.

The finding in this study that the occurrence of intrapartum fetal distress was statistically significantly higher in the borderline AFI group is in keeping with that of previous studies.[11],[25],[26] Wood et al.,[27] Rutherford et al.,[10] and Banks et al.,[12] in their studies however had contrary findings. They found no statistically significant difference in the rate of fetal intolerance of labor in pregnancies with a borderline AFI compared to those with a normal AFI.

A low 5-min Apgar score clearly confers an increased relative risk of cerebral palsy, reported to be as high as 20-fold to 100-fold over that of infants with a 5-min Apgar score of 7–10.[28] Women with borderline AFI had babies who were two times more likely to have 5th min Apgar scores less than 7. This finding was in keeping with previous studies of Kwon et al.,[17] Gumus et al.[11] and Asgharnia et al.[1] However, the findings of a study by Banks and Miller[12] are at variance with the findings of this study. It is likely that the fact that their study population included women with preterm and post-term pregnancies would explain the different findings.

Birth weight may be influenced by several factors during pregnancy, one of which is liquor volume.[29] In this study, there was a statistically significant difference between both study groups in terms of birthweight <2.5 kg.

This is in line with the findings of several studies.[1],[17],[18],[30] This finding was however in contrast with the study by Baron et al.[31] This may be due to the fact that in Baron's study, patients were recruited from a gestational age of ≥26 weeks and during labor, therefore events during the antepartum period may have had an effect on their findings could not be established.

The strengths of this study include its prospective design and matching of the possible confounding variables which increases the chance that the findings of the study are valid and generalizable to a similar study population in Nigeria. The use of dedicated outcome personnel also minimized interobserver errors and ensured accurate outcome data for the variables of interest.

The study is not without limitations. The use of cardiotocography alone for the diagnosis of intrapartum hypoxia without the benefit of confirmatory modalities like fetal scalp blood sampling, fetal scalp lactate, fetal pulse oximetry, and fetal electrocardiograph (ST- Analyzer or STAN) may have affected the rate of intervention in labor. However, since both arms of the study had cardiotocography (CTG) monitoring when indicated, the differential effect on any of the two arms is expected to be minimal.


   Conclusion Top


The findings from this study suggest the increased risk of adverse pregnancy outcomes in low-risk Nigerian women with borderline AFI such as induction of labor, assisted vaginal delivery, cesarean section, intrapartum fetal distress, Apgar score <7 in 5 min, and birthweight <2.5 kg. As such, due to the lack of a definite care protocol and specific decision about delivery for these patients, there is thus a need for the establishment and formulation of protocols on the management of these patients with borderline AFI whereby closer observation and increased antepartum surveillance be instituted in order to avoid the adverse perinatal outcome.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

This was a personally funded study.

Conflicts of interest

There are no conflicts of interest.



 
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