| dc.description.abstract | Preterm birth is defined as childbirth occurring at less than 36 completed weeks or
259 days of gestation (World Health Organization, 2014). In most developing and
resource limited countries such as Zambia, ultrasound estimation of fetal weight in
most circumstances is not readily available for the health care professional to make
decisions, a gap which can be filled by a cheaper and simpler clinical method of
estimation fetal weight. One such method is the Dare’s formula which relies on the
product of the symphysio-fundal height and abdominal circumference to estimate the
fetal weight. The study aimed at exploring this alternative clinical method to estimate
fetal weight among women at highest risk of preterm birth in a low resource
population and validate it with the actual birthweight.
This was a prospective study on mothers admitted to University Teaching Hospital
(UTH) at risk of preterm delivery. Between 1st June and 31st October 2016, a
structured questionnaire was used to collect pregnancy and outcome data on a sample
size of 168 mothers that had a singleton pregnancy, longitudinal lie and known
gestation <37 weeks about to deliver within one week. Maternal anthropometrics
included height, weight, abdominal circumference and fundal height. The derived
(estimated) fetal weight calculated using Dare’s formula was compared to the actual
birthweight. Paired t-test was used to compare the mean between derived and actual
weights. Multivariate analysis was used to understand what maternal or pregnancy
characteristics could have led to the variance (under and over-estimate beyond 300g
or 10%).
Of the 168 women enrolled, over half were moderate to late preterm (32 to 37 weeks)
with 134 (79.8%) were between 32-37 weeks with 54.2% between 34-<37 weeks.
Very Preterm were 29 (17.3%) and only 5 (3%) were <28 weeks. Using Dare’s
formula. The derived birthweight was on average 553g greater than actual birthweight
(SD = 641, 95% confidence interval 456– 651, p<0.0001). There was a 71.5% chance
of variance beyond 300g. On multivariate analysis for every 1cm increase in fundal
height measurement the odds for above 300g weight variance reduced on average by
14% (aOR =0.86, 95% CI = 0.76 - 0.98, P= 0.0249). Similarly, for every 1cm increase
in maternal abdominal circumference measurement, the odds for above 300g weight
difference increased on average by 7% [adjusted Odds Ratio (aOR) = 1.07, 95%
Confidence Interval (CI) = 1.03 - 1.12, P= <0.001].
Based on this study population, this clinical method and using Dare’s formula cannot
be reliably used in estimation of fetal weight in preterm pregnancies. Ultrasonography
remains the gold standard for determining fetal weight in preterm pregnancies and
should therefore be availed as part of the tools to help in counselling mothers on
perinatal prognosis.
Key words: Preterm birth, Fetal weight estimation | en |
