5. Simulation of the contractor’s behavior
5.1. The unbundling case
CHAPTER FIVE
pregnancy among the mothers seen during the period of this study.
Nine (2.3%) of the mothers who participated in the study claimed to have used potentially ototoxic drugs during pregnancy (Table 4). Commonly used drugs were Chloroquine and Quinine. A total of 168 (42.18%) of the mothers admitted to using native herbal medication during pregnancy (Table 5). Many however did not know the composition of the concoction ingested.
In analyzing the risk factors in the neonate, only 9(2.3%) of the neonates were found to have been delivered at less than 36 completed weeks of gestation (table 6.).
A large proportion of the neonates, 365(91.3%) of the neonates were delivered by spontaneous vaginal delivery while 34(8.5%) were delivered by means of caesarean section. (Table 7) Only one neonate was delivered by vacuum assisted delivery. A high proportion of the neonates, (78%), were delivered in the hospital while 88 (22%) were delivered at home.
Twenty four (6%) of the neonates had a delayed onset of a cry (? birth asphyxia) following birth (Table 9).
The birth weight of a majority of the neonates was in the region of 2.5 kg or more.
None of the neonates weighed less than 1500 grams (Table 10).
A total of 18(4.5%) of the screened neonates were admitted into the neonatal 31
intensive care unit (Table 12). The reasons for the admissions were however varied. The reasons ranged from macrosomia, hypoglycaemia to neonatal sepsis.
Of the neonates studied, none required incubator care.
A total of 13(3.3%) of the neonates were exposed to ototoxic medication during their admission in the neonatal intensive care unit (Table 13).
None of the neonates had obvious craniofacial or other obvious congenital abnormalities.
Of the 400 neonates studied, making up 800 ears screened for the presence of OAEs, 116(14.5%) did not have emission in one ear while 26(6.5%) failed the screening test in both ears. Of those failing the test in both ears, 12 were males while 14 were females. Only one of the neonates failing the screening test had a positive family history of hearing loss. The affected member of the family was a parent. Analysis showed no statistical significance.
Of the 51 mothers who had fever during pregnancy, only 5 neonates born by these mothers failed the test (Table 7.).
Of the nine mothers who used ototoxic drugs during pregnancy, 3 of the neonates by these mothers failed the test. This was found to be statistically significant. Of the 168 mothers with a history of use herbal medication during pregnancy, only 5 of the neonates failed the test. This was not found to be statistically significant.
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Table1: Sex distribution of the neonates Sex Frequency Percentage
Female 182 45.5%
Male 218 54.5%
Total 400 100%
Table 2: Family history of hearing loss and result of screening test OAE Results
Family history of hearing loss
Pass Refer Total
Yes 20(5.0%) 1(0.3%) 21(5.3%)
No 354(88.5%) 25(6.3%) 379(94.8%)
Total 374(93.5%) 26(5.57%) 400(100%)
Pearson’s Chi square 0.110
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Table 3: Maternal fever in first trimester and results of screening test OAE Results
Maternal fever in pregnancy
Pass Refer Total
Yes 44(11%) 7(1.8%) 51(12.8%)
No 330(82.5%) 19(4.8%) 349(87.3%)
Total 374(93.5%) 26(6.5%) 400(100%)
Table 4: Ototoxic drug use in pregnancy and result of screening OAE Result
Ototoxic drug use in pregnancy
Pass Refer Total
Yes 5(1.3%) 4(1.0%) 9(2.3%)
No 363(90.8%) 20(5.0%) 383(95.8%)
No response 6(1.5%) 2(0.5%) 8(2.0%)
Total 374(93.5%) 26(6.5%) 400(100%)
Pearson’s Chi square 0.01
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Table 5: Use of native herbal medication in pregnancy and screening results.
OAE Results Herbal med in
pregnancy
Pass Refer Total
Yes 160(40%) 8(2.0%) 168(42%)
No 211(52.8%) 18(4.5%) 229(57.3%)
No response 3(0.8%) 0(0%) 3(0.8%)
Total 374(93.5%) 26(6.5%) 400(100%)
Pearson’s Chi square = 0.419 p> 0.05
Table 6: Gestational age and OAE
OAE Results
Gestational age Pass Refer Total
< 36 weeks 8(2.0%) 1(0.3%) 9(2.3%)
= or >36 weeks 366(91.5%) 25(6.3%) 391(96.8%)
Total 374(93.5%) 26(6.5%) 400(100%)
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Table 7: Mode of delivery and results of hearing screening OAE Results
Mode of delivery Pass Refer Total
S V D 340(85.0%) 25(6.3%) 365(91.3%)
Instrumental 0 1(0.3%) 1(0.3%)
Caesarean section 34(8.5%) - 34(8.5%)
Total 374(93.5%) 21(6.5%) 400(100%)
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Table 8: Place of delivery and screening results.
OAE Results
Place of delivery Pass Refer Total
Home 70(17.5%) 5(1.3%) 75(18.8%)
TBA 13(3.3%) 0 13(3.3%)
Hospital 291(72.8%) 21(5.3%) 312(78.0%)
Total 374(93.5%) 26(6.5%) 400(100%)
Table 9: Cry at birth (? birth asphyxia) and screening results OAE Results
Did child cry @ birth?
Pass Refer Total
Yes 350(87.5%) 21(5.3%) 371(92.8%)
No 19(4.8%) 5(1.3%) 24(6.0%)
Do not know 5(1.3%) 0 5(1.3%)
Total 374(93.5%) 26(6.5%) 400(100%)
Pearson’s chi square 0.012
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Table 10: Birth Weight and Hearing Screening OAE Results
Birth weight Pass Refer Total
1.5-2.5kg 14(3.5%) 3(0.8%) 17(4.3%)
>2.5kg 264(66%) 18(4.5%) 282(70.5%)
Do not know 96(24%) 5(1.3%) 101(25.3%)
Total 374(93.5%) 26(6.5%) 400(100%)
Pearson’s chi square 0.144
Table 11: Neonatal jaundice and result of newborn hearing screening test OAE Results
Neonatal jaundice Pass Refer Total
Yes 3(0.8%) 2(0.5%) 5(1.3%)
No 371(92.8%) 24(6.0%) 395(98.8%)
Total 374(94.43%) 26(6.5%) 400(100%)
Pearson’s Chi square 0.002
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Table 12: Neonatal intensive care unit admission and result of newborn hearing screening test
OAE Results
NICU Admission Pass Refer Total
Yes 15(3.8%) 3(0.8%) 18(4.5%)
No 359(89.8%) 23(5.8%) 382(95.5%)
Total 374(93.5%) 26(6.5%) 400(100%)
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Table 13:
Effect of ototoxic drug use during neonatal period and result of newborn hearing screening test.
OAE RESULTS Ototoxic drugs in
neonates
Pass (ears) Refer (ears) Total
Yes 10(2.5%) 3(0.8%) 13(3.3%)
No 364(91.1%) 23(5.8%) 387(96.8%)
Total 374(93.5%) 26(6.5%) 400(100%)
Chi square = 0.047
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CHAPTER SIX DISCUSSION
Newborn hearing screening is a relatively new practice in Nigeria. This study sought to find out the prevalence of hearing loss among neonates in Benin City using Distortion Product Otoacoustic Emissions (DPOAE). A total of 400 neonates participated in the study.
Absence of emissions in both ears was taken as the neonate failing the test while its presence in one or both ears was considered as a pass.
This however means that some of the neonates with a unilateral hearing loss would be considered as having normal hearing. We do know that bilateral hearing loss is more debilitating than a unilateral one in terms of language metrics. A referral rate of 6.5% was obtained for bilateral hearing loss. While a referral rate of 14.57% was obtained for unilateral hearing loss. This is similar to findings by Swanepoel et al in South Africa48.
The statistically significant risk factors noted in this study were ; maternal febrile illness in first trimester of pregnancy, use of potentially ototoxic drugs during pregnancy, the mode of delivery, neonatal jaundice and the use of ototoxic drugs during the neonatal period.
The follow –up return rate in this study was 7.7%. This is not close to the follow – 41
up return rate found in Brazil—where 82% return rate was documented25. It is relatively low, when compared to a South African study where follow –up return rate was 40%48 and in a study in Lagos where the follow –up return rate 57%47. Those who came for follow-up were 2 neonates who were initially referred. One passed the repeat screening while the other did not .The neonate who was referred on the repeat screening was then referred for full audiologic evaluation. This poor follow –up rate would definitely undermine the programme’s ability to detect hearing loss. The reason for this low follow – up rate may not be unrelated to the reluctance of these mothers to visit the health centre, when by their standards of assessment their babies are well. Health centres are usually thought to cater only for the sick. Maternal education during the ante natal period about the importance of the screening would improve the follow-up rate.
Many births occur outside the hospital. Of the 365 births by spontaneous vaginal delivery, only 312 (78%) were delivered in the hospital. This is similar to other studies and underlies the difficulty in carrying out screening soon after birth or on discharge from the hospital. The rest 88 (22%) were delivered at home where there is no resuscitation equipment. These neonates are likely to be at risk of asphyxia. However, the Apgar scores of these neonates could not be ascertained, hence the degree of birth asphyxia could not be ascertained.
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Many of the mothers, though claiming utilization of antenatal services, still used native herbal medication alongside the prescribed drugs. Although the use of native medication during pregnancy was not statistically significant, more studies may need to be carried out to ascertain the active components of these preparations.
The use of ototoxic medication during the first trimester of pregnancy is a statistically significant risk factor and this is in keeping with the risk factors listed by the JCIH43.
In this study, more referral rates were found among those delivered by spontaneous vaginal delivery. This may not be unrelated to poor neonatal resuscitation facilities following birth. Only one vacuum delivery was encountered among the studied population. More research would need to be carried out but this finding may not be unrelated to the high rate of birth that takes place outside the hospital with the attendant risk of birth asphyxia.
Hyperbilirubinemia is a well recognized risk factor for hearing loss. It was found to be statistically significant in this study. The studied neonates who developed jaundice underwent phototherapy. The bilirubin levels were not known to the mothers. None of them had to undergo exchange blood transfusion. Hearing loss in hyperbilirubinaemia is neural. Cochlea function is usually preserved and 43
otoacoustic emissions are usually present in this group of neonates. The auditory brainstem response is usually abnormal41. There is a need for caution therefore in the interpretation of this result. An ABR test should ideally be the next stage in the screening. This could not be done as there is no ABR machine in Benin City.
The use of ototoxic drugs during the neonatal period was found to be statistically significant in this study. This corroborates findings in other studies where certain drugs have been found to be ototoxic52. The drugs implicated in this study were; chloroquin, quinine and aminoglycoside. The first two drugs which are synthetic quinolones are believed to cause hearing loss by vasculitis and ischaemia while aminoglycoside antibiotics are said to cause hearing loss by binding to the phospholipid phosphatydlinositol biosulphate in the cell and mitochondria leading to increase in cell permeability. This permeability leads to loss of magnesium, a cofactor in oxidative phosphorylation and subsequently cell death. First-row outer hair cells (OHCs) in the basal turn tend to be affected earlier than inner apical cells, hence the loss is usually in the high frequencies and type I cells are affected before type II cells.
The cost implication of starting a full -fledged UNHS will no doubt be enormous as such, it would seem logical to start with targeted screening of those at risk and with time to include all newborn as recommended by UNHS. The high rate of 44
delivery outside hospitals would also interfere with attaining the goals of the UNHS in screening neonates in both well baby nurseries and those in neonatal intensive care units (NICU).
With the foregoing, incorporating newborn hearing screening into the maternal and Child health programme seems a logical option for its successful implementation in Nigeria. Those not screened at the hospitals at birth will be screened at the immunisation clinics.
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