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Comparative study between unengaged and engaged fetal head in primigravida at term or in labour

Labour is an important event with unique experience exclusively in a woman’s life. It is characterized by uterine contraction that affect the dilatation of cervix and force the foetus through the birth canal. Engagement of head has been defined as passage of widest diameter (biparietal diameter) of foetal skull through the plane of the pelvic inlet. It is generally accepted that high foetal station in primigravidas in labour near term may indicate a threat to the normal progress of labour because of foetopelvic disproportion or obstruction of the foetal passage by tumor or the placenta. Although the engagement of the foetal head is regarded as a phenomenon of labour, it is usually delayed in nulliparas and commonly occurs during the last few weeks of pregnancy. When engagement occurs, it is confirmatory evidence that pelvic inlet is adequate for that foetal head. However, a significant number of primigravidae still do present with unengaged head at the onset of labour.


INTRODUCTION
Labour is an important event with unique experience exclusively in a woman's life. 1 It is characterized by uterine contraction that affect the dilatation of cervix and force the foetus through the birth canal. Engagement of head has been defined as passage of widest diameter (biparietal diameter) of foetal skull through the plane of the pelvic inlet. It is generally accepted that high foetal station in primigravidas in labour near term may indicate a threat to the normal progress of labour because of foetopelvic disproportion or obstruction of the foetal passage by tumor or the placenta. 2 Although the engagement of the foetal head is regarded as a phenomenon of labour, it is usually delayed in nulliparas and commonly occurs during the last few weeks of pregnancy. 3 When engagement occurs, it is confirmatory evidence that pelvic inlet is adequate for that foetal head. However, a significant number of primigravidae still do present with unengaged head at the onset of labour. 4 Friedman and Sachtleben demonstrated that higher station at the onset of labour were associated with an increase in the duration of labour and in the incidence of dysfunctional labour patterns. 5 In study done by Thenmozhi and Iyer, engagement of head at the onset of labour was found in 15.34% cases. 6 They have observed a proportionate prolongation in the latent phase of labour in patients with high station. In prolonged labour, mother is exposed to high risk of infections, ketosis and obstructed labour while foetus has the risk of low APGAR at birth, asphyxia and meconium aspiration syndrome. 7 Therefore, an unengaged head in a nulliparous woman in active labour can be an indication for caesarean delivery. 8 However some studies have shown that a substantial proportion of them deliver vaginally with no increase in maternal or foetal morbidity and mortality. 9 Partogram is a graphic record of progress of labour and maternal and fetal condition during labour in a single sheet of paper which is useful in detecting the labour that is not progressing normally at an early stage and helpful in its management. 10 The purpose of this study was thus to find out the incidence of unengaged heads at term or at onset of labour, make partographic analysis of progress of labour in primigravida females with unengaged versus engaged head, to determine role of active medical and surgical interventions and to determine foeto-maternal morbidity.

METHODS
It is a prospective comparative study conducted at a tertiary care hospital Mumbai from May 2016 and November 2017. 377 primigravidas attended our OPD with gestational age of equal to or >37 completed weeks and <42 completed weeks either for routine ANC checkup or in labour. According to 'OPENEPI' software at 95% confidence interval and 80% power of study for sample size estimation, minimum cases required in Group 'A' is 63 and Group 'B' is 63. But since my study duration was for 18 months, I had taken 100 cases in each group.
Detailed history was taken regarding parity, duration of pregnancy and history of labour pains if present, whenever they visited us in our OPD. Gestational age was calculated according to her LMP (last menstrual period). In those patients who were not sure of their dates, gestational age was calculated based on their earliest ultrasound.
General physical examination (i.e. height and weight) and detailed obstetric examination which included abdominal examination for fundal height, lie, presentation, engagement, amount of liquor, estimated foetal weight, palpable uterine contractions and foetal heart rate. Pelvic examination was done which included following points: prominence of sacral promontory, interspinous diameter, sacral hollow and subpubic arch to rule out contracted pelvis. Ultrasound was done to confirm above findings.
Those patients who presented with labour pains were enrolled according to the inclusion and exclusion criteria and those not in labour but having fulfilled inclusion and exclusion criteria (except labour factors) were followed up with routine ANC visits till 40 weeks on OPD basis or till they go in labour whichever is earlier. Ethical committee approval was taken.
These patients were divided in 2 groups with group 'A' consisted of 230 unengaged heads and group 'B' consisted of 147 engaged foetal head in primigravida at term or in labour.
Engagement was defined as follows: the amount of foetal head felt suprapubically in finger breadth. It is estimated by number of fifths of head above pelvic brim (CRICHTONS METHOD).
Out of total 230 patients in Group A, 33 patients were lost to follow up. 63 patients were excluded as they did not fit into our inclusion and exclusion criteria as some patients developed medical complications like pregnancy induced hypertension, some came in active labour, some had non-reassuring CTG at onset of labour, some patients had contracted pelvis. Of the remaining 134 patients, first 100 patients coming in labour or at 40wks were included in present study.
Similarly, out of 147 patients in Group B, 17 patients were lost to follow up, 15 patients were excluded due to reasons as unengaged group. Of the remaining 115 patients, first 100 patients who came in labour or at 40wks were included in present study.
All the patients from both the groups who came at the onset of labour or at 40 weeks whichever was earlier, were included in present study after detailed history, clinical examination and investigation. Appropriate consent was taken of all the eligible patients who were included in present study.
At onset of labour or at 40 weeks in all eligible patients from both the groups, pelvic examination was done for pelvic adequacy and BISHOPS score was calculated in those patients not in labour requiring induction of labour at 40wks using intracervical prostaglandin PGE 2 gel.
Onset of labour was considered from time of onset of pain in lower abdomen or history of leaking per vaginum whichever is first. Those patients who were not in labour were monitored on OPD basis till 40 weeks. Those patients who were not in labour till 40 weeks and <42 weeks were induced with PGE2 gel after assessing pelvis, BISHOPS score and NST. In patients with spontaneous onset of labour, pelvic adequacy and CTG was done. Induced patients and the patients with reactive CTG at onset of labour were observed for duration of latent phase, duration of active phase and duration of second stage. Patients with inadequate uterine contractions were augmented with oxytocin.
The course of labour was recorded on partograph. Following outcomes were measured like; percentage of patients with unengaged head at term getting engaged at onset of labour or at 40 weeks, need for medical intervention like intracervical prostaglandins for induction of labour, need of oxytocin for augmentation of labour, progress of labour with total duration of labour including duration of latent phase, duration of active phase, rate of cervical dilatation in active phase, duration of second stage, intrapartal foetal distress, mode of delivery whether spontaneous vaginal delivery, assisted vaginal delivery or LSCS and the indication of LSCS, postpartal maternal outcome and neonatal outcome like APGAR score at 1st and 5 th minute and NICU stay.
Above data was entered in proforma and analysed by SPSS version.

DISCUSSION
Out of 100 patients in unengaged group, 71% patients presented with unengaged head at the onset of labour or at 40 weeks. In study conducted by Daniel roshanfeler et al incidence of unengaged heads was 71% as compared to 29% in engaged group which is similar to present study. 8 In present study in unengaged group at onset of labour or at 40 weeks, 17 (17%) were at 5/5, 23 (23%) were at 4/5 and 31 (31%) were at 3/5, 28 (28%) were at 2/5 and 1% patient was at 1/5 which was similar to Shrivastava A. in their study which had 20% free floating heads, 34% with 4/5 palpable and 46% with 3/5 palpable heads. Studies done by Malik et al and Shrivastav A et al showed similar results in week wise distribution of onset of labour. 11,12 In present study, 73 (73%) patients in unengaged group required augmentation with oxytocin as compared to 36 (36%) in engaged group. Similar results were seen in other studies like Iqbal et al in which 72 (72%) patients in unengaged group required augmentation as compared to 33 (33%) patients in engaged group and Shaikh et al study had 74 (74%) of patients with unengaged heads requiring augmentation of labour. 13,14 In study conducted by Saima chaudhary, duration of first stage of labour was 11.04+2.04 hours while the duration of second stage was 37.8+20.3 mins which is similar to present study. 15 In study conducted by Sudhir et al, duration of first stage of labour was 12.06+0.50 hours while the duration of second stage was 36.3+15.2 minutes which is similar to present study. 16 Shivamurthy HM et al showed that the mean duration of active phase and the duration of second stage was shorter in engaged group as compared to unengaged group foetal. 17 In present study in unengaged group, 63(63%) were delivered vaginally (either normally or by assisted method) and 37 (37%) were delivered through LSCS, as compared to engaged group in which 77(77%) patients delivered vaginally and 23 (23%) patients delivered by LSCS.
Iqbal et al showed that incidence of LSCS was 38 (38%) in unengaged group as compared to 15 (15%) in engaged group which was similar to present study. 13 In a study by Shivamurthy HM et al 18% of primigravida with unengaged heads had cesarean delivery compared to 6% of primigravida with engaged heads and non-progress of labour was the main reason of LSCS. 17 Mahajan    Shaikh et al in unengaged head showed that, PPH occurred in 10% women, perineal tear in 2%, wound infection in 7% while APGAR at 5 min was 7-10 in 75%, 4-6 in 20% and </=3 in 5% neonates. 10 neonates were admitted in NICU. 14 Mean birth weight in unengaged group was 2.8 kg and in engaged group it was 2.7 kg in present study.
In study done by Dayal S et al where they studied primigravidas with engaged and unengaged fetal head, they observed that the mean birth weight was 2.77 kg in the unengaged group and 2.065 kg in engaged group. 20 The difference in birth weight in 2 groups was statistically significant which is very similar to present study

CONCLUSION
In primigravida, engagement of foetal head is delayed either during term or during labour and this unengagement causes anxiety in the minds of obstetrician due to prolonged duration of labour and higher incidence of medical and surgical intervention and a risk factor for LSCS. If the attitude of watchful expectancy and timely intervention is used in these cases, especially in cases where no aetiological factor is found for unengaged head, by plotting partogram and using oxytocin judiciously when labour appears to be taking a protracted course, most of these patients will deliver vaginally with minimal maternal and foetal morbidity and will avoid hasty decisions towards caesarean section. 88 (88%) 6 (6%) 6 (6%)