Predictors of Delivery at the Expected Date of Confinement among Women in Yenagoa, Southern Nigeria

Background: The expected date of confinement is calculated using Naegle’s rule that is 280 days or 40 weeks of gestation, but it is observed that most women tend to deliver between 38 and 42 weeks. Unfortunately, only a few women deliver exactly on the expected date of confinement, the reason remains mostly unknown.

Objective: The objective of this study is to determine the percentage of women in Yenagoa that can deliver on their expected date of confinement, using the Niger Delta University Teaching Hospital as a case study. It would also determine whether maternal age, parity, tribe, body mass index, birth weight and fetal sex have a significant influence on the date of delivery.

Materials and Methods: A retrospective observational study of 3,420 pregnant women who were admitted in labour, and delivered at term in the delivery suite of the department of obstetrics and gynaecology, Niger Delta University Teaching Hospital, in Southern Nigeria. The study was carried out from 1st January 2009 to 31st December 2012. A total of 2380 booked parturients living in Yenagoa, whose last regular menstrual period was documented in their case notes, including those who had an early first-trimester ultrasound scan, were selected. Data concerning their expected dates of confinement and the actual dates of delivery were retrieved. Also retrieved were maternal age, parity, tribe, birth weight, and fetal sex. Others include maternal height and weight at booking; these were used to calculate the body mass index. The data was analyzed after that.

Results: Majority of the women in Yenagoa 85.0% delivered at term, and only a handful 7.4% delivered on the expected date of confinement. Delivery on this date was associated with low body mass index, (BMI of 18.5 kg/m2) and male babies p = 0.006. Nulliparous women were twice more likely to deliver on the EDC than multiparas, Odds Ratio = 2.44, P = 0.002, and women with average maternal age of 25-29 years were 4 times more likely to deliver on the EDC than women ≥ 35 years, Odds Ratio = 4.93, p =0.0003. Women from Yoruba living in Yenagoa delivered more on the EDC than any other tribe in Nigeria.

Conclusion: From our study, biological variables of the would-be mother and ethnicity stand out as some of the best predictors of delivery on the date of confinement among women living in Yenagoa, Southern Nigeria.