The past 20 years have seen a progressive shift away from the use of forceps in favour of the vacuum extractor as the instrument of choice [1] [2] . Although the overall rate of operative vaginal delivery has been declining, the proportion of vacuum-assisted deliveries has been increasing and now accounts for almost four times the rate of forceps-assisted vaginal births [3] . Vacuum extraction which is a common technique of assisted vaginal delivery was preferred to forceps assisted vaginal delivery because the skill is easily acquired compared to the forceps and is considered safer [4] [5] . Thus in developing countries where specialists are lacking in most facilities, it is easier to train the non-specialists doctors to use the vacuum extractor. In addition, vacuum has in-built safety mechanism; pop-off when excessive force is applied. This makes it a safe instrument even in the hands of inexperience. The ventouse can be used in the late first stage of labour at 8 cm cervical dilatation and above for foetal distress or cord prolapsed [4] . This is a very significant advantage over the forceps in African setting. By sparing these women with caesarean section, they are encouraged to return to the hospital in subsequent pregnancies [6] [7] .

The incidence of operative vaginal delivery in the United States is currently estimated at around 5%, and approximately 66% of operative vaginal deliveries were by vacuum [1] . Operative vaginal delivery rates have remained stable at between 10% and 13% in the UK, yielding safe and satisfactory outcomes for the majority of mothers and babies. However in Nigeria, vacuum delivery rates of 0.6%, 1.5%, 1.67% and 2.9% were reported in Jos, Enugu, Maiduguri and Lagos respectively [7] -[10] and they were much lower than the developed Nations.

Operative vaginal delivery is used to shorten the second stage of labour. It may be indicated for non-reassur- ing foetal status to prevent hypoxic brain damage or foetal death [11] [12] . Maternal conditions where down bearing effort is not encouraged, such as cardiac failure and hypertensive disease in pregnancy are also indications for instrumental delivery [11] . However, the decision to perform forceps or vacuum is not always straight forward. Forceps is more preferable where maternal expulsive effort is discouraged. Vacuum extraction requires maternal effort. But even in such situations like hypertensive disorders of pregnancy, vacuum extraction can yield similar result to forceps as it shortens second stage of labour with minimal maternal efforts [13] .

The following conditions must be fulfilled before application of a vacuum extractor to avoid or minimise maternal and foetal complications: the presentation must be vertex, foetal membrane must be ruptured, gestational age must not be <34 weeks, head must be engaged to rule out cephalopelvic disproportion except in case of second twin with vertex presentation, there must be 8 cm or more cervical dilatation, the bladder must be emptied, the skills must be there and patient consent must be obtained [10] [13] .

The goal of vacuum extraction is correct placement of the vacuum cup on the fetal scalp and creation of a vacuum of up to 0.8 kg/cm² to suck part of the scalp into the cup and create an artificial caput succedaneum (chignon) and then pull to deliver the baby [13] [14] . If delivery is not successfully executed after two to three pulls in a well selected patient the procedure should be abandoned [14] [15] .

Episiotomy refers to a surgical incision in the perineum designed to enlarge the vagina and assist in childbirth [1] . Although episiotomy has often accompanied operative vaginal delivery, recent evidence suggests that routine use of episiotomy with vacuum extraction is associated with an increased rather than decreased risk of perineal trauma and rectal injuries [1] . Episiotomy during operative vaginal delivery also increases the incidence of postpartum haemorrhage, perineal infection, the need for stronger analgesia [1] . Taken together, these data suggest that routine episiotomy during vacuum extraction should be discouraged. Episiotomy, however, should be given if there is imminent perineal tear [9] [13] .

Perineal laceration is the commonest maternal injury associated with ventouse delivery [16] . Other complications include annular detachment of the cervix if it was entrapped during vacuum application, cervical incompetence and uterine prolapse if traction occurs before full cervical dilatation [17] [18] .

Nearly all neonates delivered with the assistance of a vacuum will exhibit visible scalp effects to a varying degree at the site of cup attachment. However, the majority are transient and of no clinical significance to the baby, but may cause considerable anxiety to the unprepared parent [13] [18] . The more significant injuries are, more often than not, related to misplacement of the cup, excessive or poorly directed traction, or cephalopelvic disproportion. More difficult vacuum deliveries, such as in occiput posterior and transverse positioned foetus as well as foetus at midstation, predispose to increased scalp injuries. However, the majority can be avoided with good patient selection, correct cup placement, avoidance of prolonged or misguided traction, and avoidance of cup detachments (“pop-offs”) [18] .

Retinal haemorrhages occur more commonly in neonates delivered by vacuum, compared to normal spontaneous deliveries or forceps-assisted deliveries [5] [17] [18] . However, the haemorrhage is transient with no apparent long-term developmental or any ophthalmological consequences [18] . Cephalohematomas resolve within several days, but large ones may take up to several weeks, with no specific therapy required [18] [19] . A subgaleal haemorrhage is formed by ruptured emissary veins that bleed into the potential space between the scalp aponeurosis, or galea aponeurotica, and the periosteum of the cranial bones. Unlike the cephalohematoma, suture lines do not limit this potential space, thus infants can lose up to 80% of their blood volume into this potential space [18] . Affected neonate may present with symptoms of hypovolemic shock, in addition to the diffuse and dependent swelling of the cranium [18] [19] . Therefore, it is important that every neonate who undergoes a vacuum assisted delivery receives directed attention to the scalp at periodic intervals to detect evidence of diffuse swelling.

This study was carried out to determine the incidence of vacuum assisted vaginal deliveries, indications and associated maternal and fetal morbidity at the Aminu Kano Teaching Hospital, Kano, Nigeria.

This was a retrospective descriptive study carried out at the Aminu Kano Teaching Hospital, Kano Nigeria. The case records of all the patients who had vacuum assisted vaginal deliveries managed between January, 2008 and December, 2012 were retrieved. The outcome measures were the socio-demographic characteristics of the patients, indication for the vacuum delivery, complications and failed vacuum that resulted in caesarean section. The data obtained were analyzed using SPSS, and presented in tabular form using frequencies and percentages, mean and standard deviation. The number of deliveries during the study period was obtained from the statistics unit of the hospital.

22,680 patients delivered at the hospital over this 5 year period. The ventouse was used on 210 occasions giving a prevalence rate of 0.9%. Among the cases 41.2% were conducted by registrars, 47.4% by senior registrars and 11.4% by Consultants. One hundred and eighty (85.7%) had successful vacuum delivery. The failed extractions (14.3%) were delivered by caesarean section. The mean age of the patients was 23.5 ± 7 years. The mean parity was 2.2. Among the 210 mothers, 90 were primiparas, 55 were multiparas and 65 were grand multiparas. The commonest indication for the vacuum delivery was prolonged second stage of labour in 45.2% of cases. Shortening of the second stage of labour for maternal disease conditions was done in 36.7%, and foetal distress accounted for 18.1%. The commonest maternal complication was primary postpartum haemorrhage (9.5%). Foetal complication occurred in about 31% of ventouse deliveries, with the commonest (18.1%), being cephalhaematoma. Foetal asphyxia occurred in 10 (4.8%) while 8 (3.8%) had stillbirth (Tables 1-3).

The incidence rate of vacuum deliveries in this review was 0.9%. This is higher than 0.6% in Jos, but significantly lower than vacuum delivery rates of 1.5%, 1.67% and 2.9% reported from Enugu, Maiduguri, Lagos and

Ghana respectively [7] -[10] [20] . The incidence of vacuum assisted vaginal delivery in the United States is currently estimated at around 3.3% [1] [21] . An explanation of the low rate of operative vaginal delivery in general is due to the fact that majority of the procedures were performed by residents who may have reduced confidence zone with vacuum delivery and low threshold for caesarean section [7] as cesarean delivery is increasingly accessible and acceptable, reaching levels as high as 30% in the public sector and 70% in the private sector in Brazil [22] . Most of the vacuum deliveries in this study 88.3% were carried out by resident doctors (senior registrars 47.4%, registrars 41.2%) and only 11.4% by consultants, which may explain the high failed vacuum rate in this study, and call for more consultants input in the conduct of vacuum delivery. In this study, 30 (14.3%) who had failed vacuum were delivered by caesarean section because sequential use of forceps to complete the delivery have been associated with increased risk of injuries to the fetus and maternal genital tract unless the failure occurred with the fetal head visible at the outlet of the pelvis [23] (Figure 1).

With a mean age of 23.5 ± 7 years, this study revealed that most of the parturients who had vacuum deliveries were young adults. This study also revealed that vacuum deliveries were more frequently performed in primigravida, who constituted 42.9% of parturients in this study. Similar observations were made in Jos Canada and the United Kingdom which may not be unconnected with the higher tendency to second stage delays in primigravida [8] [24] [25] , which was the most common indication for operative vaginal delivery in this study. Tight, untested lower genital tracts, undue anxiety, and inexperience in labour among young aged primigravida no doubt accounted for the higher frequency of this diagnosis.

Operative vaginal delivery is used to shorten the second stage of labour. It may be indicated for prolonged second stage of labour, maternal exhaustion or foetal conditions including non-reassuring foetal status to prevent hypoxic brain damage or foetal death [12] [13] [24] . Prolonged second stage of labour was the most common indication in our study and accounted for 45.2% which was similar to other studies in Jos and Maiduguri [8] [9] . Shortening of the second stage of labour for maternal disease conditions where bearing down effort is not encouraged was done in 36.7%. This was comparable to 38.0% in Jos [8] . The commonest maternal complication was primary postpartum haemorrhage (9.5%). This was similar to the finding in Enugu [7] . Prolonged labour, and genital tract laceration may explain this [25] . Thus, there is need to anticipate postpartum haemorrhage in operative vaginal deliveries and therefore third stage of labour should be managed actively and genital tract lacerations repaired immediately to minimise blood loss.

Vacuum deliveries can cause significant fetal morbidity [1] . This occurred in about 31% of ventouse deliveries in this study, with the commonest (18.1%), being cephalhaematoma. Significantly higher rates of cephalhematomas have been reported in other studies after vacuum application [26] -[28] . The rates of sever birth asphyxia and stillbirth were 4.8% and 3.8% respectively. This compares to the findings of various studies and may not be truly attributable to the procedure as the asphyxia may be the outcome of the events of labour that indicated the intervention than from the operative vaginal procedure itself [1] [8] [29] . Paediatricians should be notified whenever an operative vaginal delivery has been attempted and whether it was successful because serious morbidity can present several hours after birth [1] [26] [30] .

The commonest indication for vacuum delivery was prolonged second stage and the complication was minimal. The incidence of vacuum delivery is currently low. In order to reverse the trend and for this skill to continue, active training in the art of vacuum delivery is clearly needed during residency training. With appropriate training and careful patient selection, vacuum is a valuable and safe tool in the hands of the practicing obstetricians.