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Introduction: Fetal head descent is used to demonstrate the maternal pelvis capacity to accommodate the fetal head. This is especially important in low resource settings that have high rates of childbirth related maternal deaths and morbidity. This study looked at maternal height and an additional measure, maternal pelvis height, from automotive engineering. The objective of the study was to determine the associations between maternal: height and pelvis height with the rate of fetal head descent in expectant Ugandan mothers. Methods: This was a cross sectional study on 1265 singleton mothers attending antenatal clinics at five hospitals in various parts of Uganda. In addition to the routine antenatal examination, each mother had their pelvis height recorded following informed consent. Survival analysis was done using STATA 12. Results: It was found that 27% of mothers had fetal head descent with an incident rate of 0.028 per week after the 25th week of pregnancy. Significant associations were observed between the rate of fetal head descent with: maternal height (Adj Haz ratio 0.93 P<0.01) and maternal pelvis height (Adj Haz ratio 1.15 P<0.01). Conclusion: The significant associations observed between maternal: height and pelvis height with rate of fetal head descent, demonstrate a need for further study of maternal pelvis height as an additional decision support tool for screening mothers in low resource settings.
This was a multi site cross sectional study on 1265 antenatal visit records and examinations of mothers whose key descriptive information is summarized in Table 1. Included in this study were mothers whose gestational age was between 25-40 weeks of pregnancy based on their symphysio-fundal height measurement, made in centimeters by an experienced midwife after obtaining informed consent. During the 14 months of the study starting January 2013 only mothers with a singleton pregnancy were included in the study. These mothers were recruited on each day from each of the participating study site antenatal clinics by a team of previously trained midwives on duty that day. Mothers were recruited from various hospitals in Uganda that included: the National Tertiary Care teaching hospital (Mulago National Referral Hospital), Komamboga health center 4 (in Kampala central Uganda), Kagando hospital (western Uganda), St. Josephs Kitgum hospital (Northern Uganda) and Kilembe hospital (Western Uganda). A summary of the descriptive characteristic of the study population by site is provided in Table 2. Descriptive statistics of the study population Descriptive statistics for the study population by site The target sample size was calculated using the sample size calculator for Cox PH regression in STATA 12 to give 1102 mothers, using values from a study pilot for the following input parameters: alpha 0.05, hazard ratio 0.7, power 0.9 withdraws at 70% and expected number of events (fetal head descent) 331. This was inflated by a design effect of 1.15 for the 5 sites to give a total sample size of 1268 participants [20] For each mother, the following information was obtained: Age in years, height in centimeters and weight in kilograms measured using the available hospital equipment [21], gravidity, fetal presentation of the current pregnacy, head descent and symphysio-fundal height in centimeters on clinical examination to the nearest 0.1 centimeter. For each mother the pelvis height in centimeters was measured twice at the time of examination by the attending midwife, using the anterior superior illiac spine (ASIS) and the Symphysis pubis bony body landmarks using a pair of transperent rigid rulers placed at right angles to each other, as demonstrated in Figure 1 (see lines AB and BC). The average of these two measurements was used for analysis. The midwives at each site were trained in how to measure pelvis height and taken through the questionaire at the start of the study with additional refresher trainning and mentorship during the site visits by IGM. Demonstrating pelvis height using surface landmarks on the female human body Data was entered into Epidata version 3.2 (Epidata association, Denmark) and exported to STATA 12 (StataCorp LP, Texas, USA) for analysis. The focus of the analysis was on the association between the time to the key endpoint variable was defined as the antenatal visit in which a mother was observed to have fetal head descent on routine clinical obstertic abdominal examination by the research assistant nurse at the given site, with the study anthropometric measurements of maternal height and maternal pelvis height. Survial analysis was used to cater for the time to event nature of the above key end point variable. Also the maternal pelvis height used here is the same as the pelvis height currently used in automotive engineering to delineate the portion of height corresponding to the pelvis in crash test dummies [22]. The maternal pelvis height cut off of 7.50cm [23] was used to generate two groups: the first with pelvis height of less than or equal to 7.49cm and the other group greater than 7.50cm. For maternal height, grouping was done using the traditional cut off value of 150cm to generate two groups: the first with Maternal height of less than or equal to150cm and the other group greater than 150cm. Descriptive statistics were generated using: mean, ANOVA, log rank test, pair wise correlations and Kaplan-Meir survival graph plots for groups generated using the cutoff of 7.50cm [23] for pelvis height. This was then followed by univariable Cox regression modeling. To cater for the study design mulitlevel multivariable discrete time survival analysis using the gllamm function was used to calculate both the harzard ratios. During analysis any record found with a missing value was dropped from analysis and a P <0.05 was considered significant for all tests. Ethical considerations for this study included obtaining ethical approval from the Makerere University School of Biomedical Sceinces IRB and the study was registered with the Uganda National of Science and Technology. The hospital administrators and heads of units were briefed of the study and the need to obtain a copy of the Antenatal record. All the participating nursing staff were requested verbaly to be part of the study and offered an equivalent of 1US dollar compensation for each Antenatal record filled to completion. For the mothers, each was requried to sign an informed consent form to participate in the study. Informed consent was obtained by the attending midwife for visit. Young mothers less than 18 years, the age of consent in Uganda were handled as emancipated adults and all women were free to consult their spouses or next of kin since the study required one to provide contact information as part of the consent process. With the exception of measuring maternal pelvis height there were no other procedure or modification made to the current routine Antenatal practices at any of the participating sites. Refusal to consent did not result in a mother bieng denied access to health care or required services at the particpating faclity. No identifier marks or personal information was used in the analysis and subsequesnt reporting of the study results.
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