Twin births in the university of Portharcourt tea

　　　　　　 作者：Onyearugha CN， Ugboma HAA

【摘要】 　　Objective:To provide information on twin births and associated factors in Port barcourt South South Nigeria. Methods: Data on twin deliveries from 1st January 2003 to 31st December 2008 were collected and analysed. This included the maternal age and parity， gestation age，Apqar scores， sex and birth weight of twins. Results: A total of 11042 deliveries occurred over the study period with 333 being twins giving a twin rate of 1∶33. Male twins constituted 48% of twin births with male to female ratio of 1∶1.08. The mean age and parity of mothers were 29.6 years and 2.5 respectively. Presentation of the cephalic/cephalic for the first and second twins was the most common (63.4%). Severe birth asphyxia (first minute Apgar score 13) occurred in 3.9% of twins.Malemale twin pair occurred in 28.5% of twins， malefemale in 39% while femalefemale occurred in 32.5%. The Caesarian section rate was 48%.Conclusion: The twining rate in this study is high. In this locality， there is a need for early ultrasound scanning of pregnant women particularly those of parities 1 to 3 and those aged 2534 years in whom highest rates of twinning occurred to detect twinning when present and refer them to sufficiently equipped centres for adequate antenatal and perinatal care.

【关键词】 Twin births; Review; Port Harcourt

　　INTRODUCTION
　　
　　The incidence of twin delivery is highly variable in different parts of the world being highest among blacks(1 in 80 pregnancies); lowest among oriental races including Japan and China (1 in 155 pregnancies) and intermediate in North European whites (1 in 100 pregnancies)［13］.

　　The incidence could also be increased by the use of fertility drugs for induction of ovulation［4］. It has also been reported that twin delivery could occur more in rural than urban population of same geographic and racial setting［5］.

　　Nigeria is recorded as having the highest incidence of twin births world wide［6］. Though the incidence of twin delivery in Nigeria is reported to be highest in the Yoruba ethnic group of the West at about 1 in 19 pregnancies， it is inconsistent in the Northern region where twin rates of 1:25， 1:43， were recorded and South eastern states where incidence of 1∶18， 1∶24， 1∶3335 have been documented［49］.
　　
　　Twins are high risk infants resulting from high risk pregnancy often associated with maternal and foetal complications including pre eclampsia， prematurity， low birth weight， intrauterine growth restriction， respiratory distress syndrome， birth asphyxia， as well as retained second twin with attendant high perinatal， and maternal morbidity and mortality［4］. It has been documented that perinatal mortality associated with twin pregnancy is 4fold more than that with singleton pregnancy and that this is related to high incidences of intrauterine growth retardation， prematurity， fetal distress， fetal anomaly and maternal preeclampsia［10］. Intrauterine growth restriction occurs in up to 67% of twins［11］.There is dearth of published works on twin births in Port harcourt， South south Nigeria. This study is undertaken to determine the incidence of twin births and related factors in Port Harcourt.
　　
　　The results are expected to provide obstetricians， anaesthesiologists and paediatricians involved in twin delivery and management with a better understanding of the subject thereby enhancing effective management.

　　materials and method
　　
　　This was a retrospective study conducted in the Department of Obstetrics and Gynaecology of the University of Portharcourt Teaching Hospital (UPTH) Port Harcourt Nigeria over a sixyear period (1st January 2003 to 31st December 2008). Information constituting the obstetric， maternal and foetal data was obtained from obstetric registers in the labour and isolation wards and the main theatre as well as by retrieval and scrutiny of obstetric case notes from Medical Records Department to fill information gaps where necessary. Details of information obtained included age， parity and booking status of mothers， gestational age， mode of delivery， sex and birth weight of twins and overall number of deliveries over the study period.
　　
　　Data was recorded in flow data sheets and analysed by simple arithmetic mean， frequency distribution and presented in tables.

　　RESULLTS
　　
　　During the period under review there was a total of 11042 deliveries with 333 of them being twin deliveries giving an incidence of 3% or 1∶33.(Table 1)

　　The age of mothers ranged from 17 to 45 years while the parity ranged from 1 to 9 with the mean age and parity being 26.9 years and 2.5 respectively Tables 2 and 3.

　　The rate of twinning was lowest amongst teenagers and mothers aged 40 years and above (1.2% and 1.6% respectively) and was highest at ages 2534 years (73.2% collectively)( Table 2)

　　Twining rates were highest in parities 1，2 and 3 (76.8% collectively) and lowest in parities 4 and above (23.8% collectively)(Table 2)

　　The gestational age at delivery ranged from 22 to 43 weeks with a mean of 36.9 weeks. Preterm deliveries constituted 32.1% of twin deliveries and postmature births constituted 1.5% (Table 3).
　　
　　Thirty five point nine percent of the twins weighed less than 2 500 g at birth with only one weighing above 4 000 g (Table 3).Table 1 Foetal outcome of twin deliveries（略）

　　Majority of the sets of twins (39%) were male/female gender while the male/male combination was smallest in frequency constituting 28.5%(Table 3).

　　Caesarian section rate was 48.3% and constituted the commonest method of delivery while only 1 set of twins was delivered using forceps (Table 4).
　　
　　Cephalic/cephalic presentation was by far the commonest twin presentation at birth. Cephalic/breech constituted 17.7% while
breech/breech were 9.0% of total presentation.
　　
　　Twenty six (3.9%) of the twins were severely asphyxiated at birth (Apgar score 13 ) while 141 (21.2%) had moderate birth asphyxia (Table 4).　　 Table 2 Antenatal data of mothers of twins （略）
Table 3 Demographic data of twins. （略）Table 4 Delivery data of twins（略）

　　DISCUSSION
　　
　　Onyearugha CN et al. Twin births in the university of Portharcourt teaching hospital Portharcourt: a 6 year review It is well documented that twinning occurs more commonly in blacks than in Caucasians and that Nigeria has the highest twinning rate in the world［6，12］. Rates of twinning reported from different geographic zones and within same geographic regions of Nigeria vary widely. However rates obtained from rural areas tend to be lower than those from hospitals located in urban centres.

　　The incidence of twin births of 1∶33 deliveries obtained in this study is similar to reported rates of 1∶33 35 in the Igbos of south east region of Nigeria but higher than the rates of 1∶47; 1∶43 in Lagos and Jos Nigeria respectively and 1∶67 or more in Caucasians but definitely lower than 1 in 1922， 1∶18; 1 in 24 and 1 in 25 obtained in Ibadan of the West ， Umuahia and Afikpo of the Southeast， and HausaFulani of the Northern Nigeria respectively ［5，7，8，9，13，14］.

　　The similarity of incidence of twin births in this study and that obtained by J.C Azubuike in University of Nigeria Teaching Hospital Enugu may be explained by the fact Port Harcourt and Enugu though in different more localized zones of Nigeria now， belong to same wider geographical location East of the Niger River. Moreover， the Igbos constitute a high percentage of the population in Port Harcourt . Also， this study like the one conducted in Enugu is an urban tertiary institution based study. Highest twining rates of 19 and 18 obtained in rural areas of Western and Eastern Nigeria when compared with our result still support previous reports that twinning occurs more in rural than urban population［5.6.14］.

　　The exact explanation for this is not readily clear. However it could be partly due to the fact that rural women often prefer delivering in familiar local delivery places including traditional birth attendants' place to the more distant urban Teaching Hospitals［9，15］and are only inevitably referred there when labour becomes complicated.
　　
　　The result of this study is in conformity with previous reports that twinning rate rises with increasing maternal age up to midthirties after which it drops sharply［5，6，15］.

　　Although twinning rates have been previously documented to increase steadily with ascending birth rank 5，6，14. Our result indicates higher and approximately equal rates (24.6%， 27.6%， 24.6%) amongst parities 1，2 and 3 respectively descending sharply thereafter in higher birth ranks.

　　It is reported that spontaneous preterm delivery occurs in about 30% of twin pregnancies［10］. Our study reveals a similar preterm delivery of 32.1% which also is close to other previous reports from United kingdom and Jos， Nigeria［4，10］.

　　Our study result indicates 35.9% of twins weighed less than 2 500 grams. This is much lower than approximately 50% of twins weighing less than 2 500 grams in previous studies from Jos and Afikpo， Nigeria［4，9］.

　　This disparity is not readily explanable though it could be related to the fact that over 87% of the mothers in our study as compared to 76% in Jos were booked in the Teaching Hospitals and therefore more likely to be exposed to better prenatal care.
　　
　　The highest frequency of cephalic/cephalic presentation followed by cephalic/breech and breech/breech in descending order was observed in our study. This confirms a similar observation in some previous studies from Jos and Afikpo. However cephalic/cephalic presentation constituted 63.4% of twin presentation in our study and is much higher 48% and 46.3% it recorded respectively in those centres［4， 9 ］.
　　
　　The Caesarian section (CS) rate in our study is 48.3%. This is higher than CS rate in many previous studies.［4，9］ It could be a factor explaining the relatively low rate(3.9%) of twins with severe birth asphyxia in our study thereby probably justifying it.

　　The difference in Apgar scores between the first and second twins is not statistically significant.

　　CONCLUSION
　　
　　This study result supports reports of Nigeria possibly being a country with highest twinning rate in the world. It also supports reports that twinning rates obtained in urban tertiary hospitals of same geographic zones in Nigeria could be similar. The high rate of preterm delivery， low birth weight， observed in this study as well as documented increased incidence of intrauterine growth retardation in twins result in high incidence of septicaemia and perinatal mortality. To curb this ugly consequence， government at all levels must provide free quality antenatal and perinatal services to the citizenry. Cases of twin pregnancies once diagnosed must be referred to appropriately equipped centres for further antenatal and perinatal care. There is an urgent need to site well equipped adequately staffed 10 secondary health care facilities as closely as possible to where people live and work. Appropriate policies for practical women empowerment must be urgently adopted and executed by government at all levels. Girl child education up to tertiary level must be made free and compulsory and sustained by the government.

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