Maternal Diabetes Mellitus and Risk of Stillbirth: A Nested Case-Control Study in a Nigerian Tertiary Hospital
Abstract
Background: Stillbirths have always been a contributor to psychological morbidity amongst women. Diabetes mellitus remains a significant risk factor for its occurrence. Knowledge of the causes and risk factors of this unfortunate problem will help in designing preventive measures to reduce its incidence.
Objective: To determine the relationship between maternal diabetes mellitus and the risk of stillbirths.
Methods: This is a nested case control study conducted in the Obstetrics unit of the Nnamdi Azikiwe University Teaching Hospital, Nnewi, Nigeria from 1st September 2014 to 31st August 2017. Forty-four women who had stillbirth were regarded as the cases and 44 women who had livebirths were regarded as the control group were retrieved from their case files. Information obtained included; type and sex of the stillborn, maternal age, type of stillbirth, parity, educational status, booking status, gestational age, and mode of delivery. Odds ratio (OR) with 95% confidence interval was calculated to determine the relationship between maternal diabetes and the risk of stillbirth.
Results: The risk of stillbirth in diabetic pregnancies irrespective of the type was found to be two times higher than in non-diabetic pregnancies (OR 2.16, 95% CI 0.72-6.30). The mean age of the women was found to be approximately 30 years in both cases and controls. The ratio of macerated stillbirth to fresh stillbirth was 1.4:1 and females were affected more than males in a ratio of 1.3:1. The mean gestational age at delivery was 35 weeks for the cases and 38 weeks for the control group. Majority of the women included in the cases had only a primary level of education (34.1%) and never accessed antenatal care services (79.5%) as against the majority of the women in the control group who had a tertiary level of education (45.5%) and were booked for antenatal care (72.7%).
Conclusion: This study established that there is a significant association between maternal diabetes mellitus and stillbirth. The increased occurrence in the cases could be due to ignorance, lack of antenatal care, low socioenomic class and poor control of glycemic levels found among the women. Hence, the need for effective preventive/control programmes for these group of women.
Keywords:Stillbirths, Diabetes mellitus, Pregnancy
Introduction
The World Health Organization (WHO) defined stillbirth as the death of a fetus with a birth weight of at least 500g or if birth weight is unavailable [1,2], a gestational age beyond the age of viability. The stillbirth rate, as the perinatal mortality rate, is an important indicator of the quality of antenatal care and obstetric care during labor and delivery [3]. Knowledge of the causes and risk factors of this unfortunate problem will help in designing preventive measures to reduce its incidence [4]. Stillbirths are common and devastating, and in developed countries, about one-third has been shown to be of unknown or unexplained origin [5]. Some factors have been identified of which few of them have a direct causal relationship such as abruptio placentae, cord accidents, etc., while others may be indirectly related such as preeclampsia, maternal diabetes, maternal smoking, obstructed labor, maternal infections during pregnancy, etc. (all of which are modifiable factors). Stillbirth is classified as fresh stillbirth when the baby is born with an intact skin suggesting that the death occurs during labor (less than 12 hours before delivery), and macerated stillbirth, when there are signs of degeneration (pealing of skin, red serous effusions in the chest and abdomen due to Haemoglobin staining) suggesting that the death occurred more than 12-24 hours before labor [5]. Macerated stillbirths are often associated with insults that occur in utero during the antenatal period.
Diabetes concurrent with pregnancy is a high-risk condition and is associated with an increased risk of perinatal mortality [6-8] especially if poorly controlled. Other complications in the newborn include hypoglycemia, macrosomia, polycythemia, hyperbilirubinemia, respiratory distress syndrome, prematurity, shoulder dystocia, congenital anomalies, etc. [9-12].
Historically, diabetic pregnancies often ended in unexplained stillbirths [7]. Several researches and attempts have been made to identify the exact cause but has not yielded much results [9-12].
Globally, about 4% of all stillbirths remain attributable to diabetes and diabetic pregnancies continue to increase the risk for perinatal mortality [13]. Before the discovery of insulin, a woman with type 1 diabetes had almost no chance of successful delivery of a healthy baby [9]. With the advent of insulin treatment, pregnancy losses continued to be high, predominantly through stillbirths [9]. According to the WHO update, there were 2.6 million stillbirths in 2015 [10,11] accounting for over 7,178 deaths per day [11]. It has been noted that 98% of these deaths occur in the low- and middleincome populations [10]. About 66% of the worldwide stillbirths is contributed by the developing nations like India, Pakistan, Nigeria, China, Democratic Republic of Congo, Ethiopia, Bangladesh, Indonesia, Tanzania, and Afghanistan[1,2].
In this study, the authors hypothesized that there was no relationship between maternal diabetes and stillbirths (if odds ratio is <1). However, there has been extensive research into the effects of diabetes mellitus on pregnancy outcomes, and in particular on the risk of stillbirths [12,14-27] though not much work has been done in Africa and relatively none in Nigeria. This study was aimed at determining the relationship between maternal diabetes mellitus and the risk of stillbirths.
Methods
This research was carried out at the Nnamdi Azikiwe University Teaching Hospital (NAUTH) Nnewi. A nested case-control design was used to determine the relationship between maternal diabetes and the risk of stillbirth. The study population included the cases (all pregnant women who were admitted and delivered stillbirths whether fresh or macerated) and controls (pregnant women who delivered live babies during the same period in the same hospital) of stillbirths that occurred from 1st September, 2014 to 31st August, 2017. Case files of women who carried their pregnancy beyond the age of viability (28 weeks) and delivered were included while case files of women who could not carry their pregnancy up to the age of viability were excluded. The data was gotten from the medical records department. Controls were randomly chosen in a ratio of 1:1 to the cases. Data extracted included the sex of the stillborn, maternal age, type of stillbirth, parity, educational status, booking status, gestational age (GA), glycemic levels. Maternal age and comorbidities were controlled to remove potential confounders. Data was analyzed and the odds ratio (OR) and 95% Confidence interval (95%CI) calculated to check for the statistical significance. This study was approved by the Ethics committee, NAUTH and permission obtained from the Head of Department, Medical Records, NAUTH, Nnewi before the patients’ case files were retrieved. Information obtained were treated with utmost confidentiality.
Results
A total of 88 case files were analyzed during the study. The women (cases and controls) had their ages ranging from 21-42 years, with a mean age of 30.1years and 20-38 age groups with a mean age of 29.6 years respectively. Up to 56.8% of the cases of stillbirths were females, while 43.2% were males giving a ratio of 1.3:1.
A total of 88 case files were analyzed during the study. The women (cases and controls) had their ages ranging from 21-42 years, with a mean age of 30.1years and 20-38 age groups with a mean age of 29.6 years respectively. Up to 56.8% of the cases of stillbirths were females, while 43.2% were males giving a ratio of 1.3:1.
The parity of the women included in the controls were analyzed, with 52.3% being multiparous, 43.2% primiparous and 4.5% grand multiparous. Up to 36.4% of the women had a secondary level of education, 45.5% tertiary level while 18.1% stopped at primary level. A majority of the women were booked (72.7%). Considering the mode of delivery, 61.4% of the women had vaginal delivery while the remainder delivered via caesarean section (38.6%). The mean gestational age at delivery for the controls was 38.0 weeks.
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