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Year : 2011  |  Volume : 14  |  Issue : 2  |  Page : 129-131

Delivery rate in Benin City, Nigeria: Are there seasonal variations?

Department of Obstetrics and Gynecology, University of Benin Teaching Hospital, Benin City, Nigeria

Date of Acceptance17-Feb-2011
Date of Web Publication19-Aug-2011

Correspondence Address:
E J Enabudoso
Department of Obstetrics and Gynecology, University of Benin Teaching Hospital, Benin City
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1119-3077.83999

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Objective : To determine if there are monthly variations in the rate of deliveries in Benin City, Nigeria.
Materials and Methods : A retrospective descriptive study carried out in the three major obstetric centers in Benin City, Nigeria. We extracted the total number of deliveries from the hospitals' records for over a five-year period and analyzed the figures for monthly variation in delivery rates. This was repeated for a standardized 30-day month and the findings noted.
Results : There were 28,686 deliveries during the study period with an average monthly delivery of 2,390. The monthly distribution showed a sinusoidal pattern with peak delivery rates in April-May and October and lowest rates in July-August and December. The months of April, May, and October had delivery rates that were significantly higher than the monthly average delivery rate, while the converse was true for July, August, and December at the 99% confidence interval.
Conclusions: There exists a significant monthly variation in delivery rates in Benin City. This finding will prove valuable in health system planning and in the interpretation of seasonal variations in other reproductive parameters.

Keywords: Delivery rate, delivery variation, monthly variation

How to cite this article:
Enabudoso E J, Okpighe A C, Gharoro E P, Okpere E E. Delivery rate in Benin City, Nigeria: Are there seasonal variations?. Niger J Clin Pract 2011;14:129-31

How to cite this URL:
Enabudoso E J, Okpighe A C, Gharoro E P, Okpere E E. Delivery rate in Benin City, Nigeria: Are there seasonal variations?. Niger J Clin Pract [serial online] 2011 [cited 2019 Jul 17];14:129-31. Available from:

   Introduction Top

Humans have the potential of year round reproduction in a cyclical pattern. A fertile woman has the potential of conception following unprotected sexual intercourse at the time of ovulation. Ovulation in humans occurs cyclically. Studies abound on the seasonal variation of various obstetric events. [1],[2] It has been shown in some studies that the incidence of eclampsia and pre-eclampsia is season-dependent. [3],[4],[5],[6],[7] The seasonal effect on the rate of ectopic pregnancy, [8],[9] spontaneous abortion, [10] and even the seasonal effect on conception has been studied with conflicting results. [4] Etard et al. also reported a seasonal variation in direct obstetric mortality in rural Senegal, although the seasonal variation noticed was not statistically significant. [11] However, many of these studies had no reference to seasonal variation in the delivery rate, as a possible variable that may have resulted in an apparent seasonal difference in the incidence of these conditions.

This study aims at reviewing the monthly distribution of deliveries. The monthly distribution of deliveries approximately reflects the monthly distribution of conception, as each term delivery reflects a conception that occurred about nine months earlier. The knowledge gained of the seasonal variation in conception and delivery will be important in various aspects of health system planning, especially those concerning reproductive health issues. In batching for assisted reproduction, the findings could assist in predicting periods of improved successful outcome. It will also assist in the better understanding of these reproductive issues and the factors that affect their occurrence. Knowledge of seasonal variation in the delivery rates may also be a necessary denominator in validating the apparent seasonal variations in various reproductive health statistics. Considering the dearth of information on the seasonal distribution of deliveries, it becomes necessary at this point in time, to document such a variation, if any, and thus provide some evidence on its existence or otherwise.

   Materials and Methods Top

This is a retrospective descriptive study carried out in three of the largest obstetric centers in Benin city, Edo state, Nigeria: (i) the University of Benin Teaching Hospital, Benin city - a tertiary health center serving as a referral center for about five million people from within and outside the state, with an annual delivery rate of 2,000 to 3,000; (ii) The Central Hospital, Benin city - a specialist hospital run as a government-owned secondary health center and also having an annual delivery rate of 2,000 to 3,000; (iii) St. Philomena Catholic Hospital, Benin city - the foremost missionary hospital in the state with an annual delivery rate of 1,000 to 2,000.

A five-year record of deliveries at these centers was extracted. The extracted data was then fed into a computer and an analysis was performed, based on the grouping of the delivery rates per month. The monthly delivery rates were standardized to a uniform 30-day month, to eliminate the disparity that may result from the differences in the number of days in the various months of the year, and the analysis was repeated. The SPSS version 16 statistical software was used to analyze the results. This study was approved by the ethical committee of the University of Benin Teaching Hospital.

   Results Top

The total number of deliveries recorded in the obstetric centers over the study period was 28,686, with an average monthly delivery of 2,390. The range of monthly deliveries was 2,102 to 2778. The monthly distribution of total deliveries showed a slightly sinusoidal pattern with two peaks: A major peak spanning two months, April and May, and another peak in October [Figure 1]. The Figure also depicted the nadir number of deliveries to occur majorly in July and August and another in December. This pattern persisted even after correction for the differential number of days in the months of the year [Figure 2].
Figure 1 : Monthly distribution of total deliveries in Benin city

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Figure 2 : Standardized monthly distribution of total deliveries in Benin City. [Number of deliveries standardized to a 30-day month]

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The percentage distribution of monthly deliveries is shown in [Table 1]. It shows that almost 40% of the annual deliveries occur in the months of March, April, May, and October. In addition, it shows the significance level of the monthly average deliveries compared to the computed overall average monthly delivery rate of 2,390. The months of April, May, and October are shown to have significantly higher monthly delivery rates and the months of July, August, and December have significantly lower average monthly delivery rates compared to the computed monthly average at the 99% confidence interval.
Table 1: Percentage distribution of average monthly deliveries

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   Discussion Top

This study found a significantly higher monthly delivery rate in the months of April, May, and October, and a significantly lower monthly delivery rate in July, August, and December. The single highest monthly delivery occurred in the month of April and the single lowest in December. This, by implication infers the highest monthly conception to be in July and the lowest monthly conception to be in March. These findings relate favorably with reports in different parts of the world, which have reported a significant variation in the monthly delivery rates. The recent National vital statistics report of the United States, reports that births peak historically in August and reach a nadir in February. [12] Studies from Norway and Australia reported seasonal variations in birth rates. [1],[2] Yadava et al. , working in India, reported the maximum indices of deliveries in the months of August to October and lowest from April to June. They extrapolated this to indicate the maximum conception rates in the winter season. [13] Warren et al. have also reported a significant bimodal seasonal trend in the estimated monthly number of conceptions. [10]

Different reasons have been adduced for the seasonal variations observed in these studies. Seasonal variations in sperm quality and also in ovarian activity have been proposed. [14] Seasonal variation in coital activity among couples is the possible factor influencing the seasonal variation in conception and delivery. Increase in cohabitation is expected in the cold seasons as in the harmattan festive seasons of December in Nigeria, but the peak conception rate was found to occur in July (which corresponds to the height of the rainy season which is often hot). The effect of photoperiod, melatonin, and temperature are other mechanisms that have also been proposed. [15] Despite these, different geographical locations will experience different months of peak and nadir in the number of deliveries, as a result of differences in altitudes and climatic conditions, [8],[16] as seen in this study compared with others from different climatic regions. [1],[2],[12]

One limitation of this study is that it is hospital-based, and therefore, failed to capture all the births in the community. Nevertheless, this is unlikely to influence the outcome of this study as Benin city is almost entirely urban and well over 70% of deliveries are hospital-based. [17] In addition, it is unlikely that there will be significant seasonal variations in access to the studied hospitals, which are located in different parts of the city. Occasional industrial action leading to closure of one or more of the hospitals is another limiting factor. This too is unlikely to affect the findings, as there has been no industrial action that has affected more than one of the centers at the same time, as they are run by different levels of management and most of the industrial actions have been short and often spared the labor wards of the hospitals from such action.

The study of seasonal variations in health and health-related issues plays a great role in understanding the variables that affect the various events. Understanding the variation in conception and delivery rates is of immense value in time-assisted reproductive procedures, in other issues relating to reproductive care, and when planning for a more efficient service delivery.

   References Top

1.Odegard W. Season of birth in the population of Norway, with particular reference to the September birth maximum. Br J Psychiatry 1977;131:339-44.  Back to cited text no. 1
2.Mathers CD, Harris RS. Seasonal distribution of births in Australia. Int J Epidemiol 1983;12:326-31.  Back to cited text no. 2
3.Subramaniam V. Seasonal variation in the incidence of preeclampsia and eclampsia in tropical climatic conditions. BMC Women's Health 2007;7:18.  Back to cited text no. 3
4.Phillips JK, Bernstein IM, Mongeon JA, Badger GJ. Seasonal variation in preeclamsia based on timing of conception. Obstet Gynecol 2004;104:1015-20.  Back to cited text no. 4
5.Makhseed M, Musini MV, Ahmed MA, Monem RA. Influence of seasonal variation on pregnancy-induced hypertension and/or preeclampsia. Aust N Z J Obstet Gynaecol 1999;39:196.  Back to cited text no. 5
6.Tam WH, Sahota DS, Lau TK, Li CY, Fung TY. Seasonal variation in pre-eclamptic rate and its association with the ambient temperature and humidity in early pregnancy. Gynecol Obstet Invest 2008;66:22-6.  Back to cited text no. 6
7.Okafor UV, Efetie RE, Ekumankama O. Eclampsia and seasonal variation in the tropics-a study in Nigeria. Pan Afr Med J 2009;2:7.  Back to cited text no. 7
8.Eskandar M, Archibong E, Sadek A, Sobande A. Ectopic pregnancy and seasonal variation: A retrospective study from the south western region of Saudi Arabia. Bahrain Med Bull 2002;24:63-5.  Back to cited text no. 8
9.Goldenberg M, Bider D, Seidman DS, Lipitz S, Mashiach S, Oelsner G. Seasonal pattern in tubal pregnancy. Gynecol Obstet Invest 1993;35:149-51.  Back to cited text no. 9
10.Warren CW, Gld J, Tyler CW, Smith JC, Allen L. Seasonal variation in spontaneous abortions. Am J Public Health 1980;70:1297-9.  Back to cited text no. 10
11.Etard JF, Kodio B, Ronsmans C. Seasonal variation in direct obstetric mortality in rural Senegal: Role of malaria? Am J Trop Med Hyg 2003;68:503-4.  Back to cited text no. 11
12.Martin JA, Hamilton BE, Ventura SJ, Menacker F, Park MM. Births: Final data for 2000. National vital statistics report. Hyattsville, Maryland: National center for health statistics 2002;50:8,45.  Back to cited text no. 12
13.Yadava KN, Dube D, Marwah SM. Astudy of seasonal trends in delivery and medical termination of pregnancy. J Obst Gynaecol India 1979;29:256-7.  Back to cited text no. 13
14.Levine RJ, Bordson BL, Matthew RM, Brown MH, Stanley JM, Star TB. Deterioration of semen quality during summer in New Orlaens. Fertil Steril 1988;49:900-7.  Back to cited text no. 14
15.Cagnacci A, Volpe A. Influence of melatonin and photoperiod on animal and human reproduction. J Endocrinol Invest 1996;19:382-411.  Back to cited text no. 15
16.Paonnenberg T, aschoff J. Annual rhythms of human reproduction and environmental correlations. J Biol Rhythms 1990;5:217-39.  Back to cited text no. 16
17.National Population Commission and ICF Macro 2009. Nigeria Demographic and health survey 2008: key findings. Calverton, Maryland, USA: NPC and ICF Macro. Available from: http://www. [Last assessed on 2010 Feb].  Back to cited text no. 17


  [Figure 1], [Figure 2]

  [Table 1]

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