INTRODUCTION:
Fetal macrosomia is defined as the birth weight greater than
4000g(4kg) or fetal birth weight above 90th percentile for the
gestational age. (3). It is a major contributor to obstetric morbidity and it
is a major cause of maternal and perinatal morbidities. (1,4)
The risk factors for fetal macrosomia are not all known, however
obesity, over weight, Diabetes mellitus, gestational diabetics, Excessive
weight gain in pregnancy, multiparity, history of previous fetal macrosomia and
male sex have all been reported in various literatures as risk factor for fetal
macrosomia. (5)
The prevalence of fetal macrosomia varies and it ranges between
8.1% to 9%, however in Sub-Sahara African, prevalence as low as 1.9% has been
reported in Ethiopia in some literature and prevalence as high as 14.6% has
been reported in Nigeria.(5) The incidence of fetal macrosomia in multiparous
women was 7.6%, but the recurrent rate of fetal macrosomia in multiparous women
was 27.2%. (4, 5) A longer gestational age in subsequent pregnancy was reported
as an independent risk factor for fetal macrosomia. (6)
Pregnant women are screened for gestational diabetic in some
centres at the gestational age of 24 – 28 weeks. (4,5) Some centres also screen
all parturient with body weight above 90kg. The screening for gestational
diabeticsis usually done with a 75g, 1hour glucose challenge test and the
parturient who failed in this test are recommended to be on a standard
euglycaemic diet and they are recommended to have glucose monitoring at home for fasting and postprandial glucose
level. (6,7) It is important to note
that pregnant women who do not meet up with specific diagnosis for gestational
diabetics mellitus may still have glucose mediated fetal macrosomia. (8)
Excessive pregnancy weight gain is also reported as an independent risk factor
for fetal macrosomia in women with intermediate gestational blood glucose. (8)
Fetal macrosomia is associated with both maternal and fetal
complications.(5,6) The maternal complications include dysfunctional uterine
contraction, prolonged labour, uterine rupture, increase risk for caesarian
Section, spontaneous symphysiotomy, Obstetric neuropathy and lower genital
tract laceration. Fetal and neonatal complications include shoulder dystocia,
Erb’sPalsy, fracture of the clavicle or humerus, neonatal Asphyxia, hypocalcemia,
hypoglycaemia, hypomagneseamia and hyperbilirubinaemia. (8,9)
Perinatal diagnosis of fetal macrosomia can be made either
clinically or through ultrasound, various clinical method of fetal weight
estimation have been reported.(9) The clinical methods of fetal weight
estimation include, the Johnson’s, Dare’s, Dawn’s, Onan’s, etc.(9) The clinical methods are simple, safe, cheap
and readily available; however they depend on the skill of the clinician.(9) These clinical methods of fetal weight
estimation arealso subjected to various degrees of Intra-observer and
inter-observer errors. (10)
Both Clinical and ultrasonographic method of fetal weight
estimation are not always predictable.(11)The heaviest baby recorded in the
Guinness book of records weighed10.2kg and this baby was born in Italy in 1955.
It was also recorded that the second biggest baby weighted 7.3kg and the baby
was delivered in Brazil. (11)
Fetal macrosomia is a serious medical concern and it is said to
have a great burden to the health facilities. (12) The knowledge of risk
factors for fetal macrosomia in our environment may reduce the prevalence
during antenatal care and consequently reduce the complications associated with
fetal macrosomia.
Health education and preconceptional care should be conducted for
multiparous women with the history of fetal macrosomia, aimed to promote
maintenance of optional pre-pregnancy body mass index thereby preventing
excessive weight gain in pregnancy and by so doing, reducing the prevalence of
fetal macrosomia in our environment.
FIGURE 1:
Macrosomic Baby
CASE
REPORT
She is a 22 year booked primgravida Nigeria woman who booked
antenatal care in our institution at the gestational age of 17 weeks; pregnancy
was spontaneously conceived and confirmed with Urine pregnancy test after 8
weeks of amenorrhoea.Prior to booking for antenatal care, pregnancy was
uneventful. At booking, the booking parameters were – pulse rate of
80beats/minute, Blood pressure was 110/80mmtts, the body weight was 69kg,
height of 160cm, body mass index was 27kg/m2, urine analysis was normal, random
blood sugar was 97mg/dl, Blood group is O Rhesus positive and the Genotype is
AS.She had intermittent preventive therapy for malaria at 24 weeks and 28 weeks
respectively with sulphadoxine – pyamethamine; she also received tetanus
immunization accordingly.
At a gestational age of 26 weeks, she had an Obstetrics ultrasound
scan who showed a single active fetus in variable lie, Estimated gestational
age of 26 weeks and expected date of delivery was 12/12/2022. She had
glycosuria (+1) at the gestational age of 33 weeks and she was requested to do
Glucose challenge test, however, she absconded and only for her to present at
the Obstetric emergency ward at the gestational age of 42 weeks with the history
of liquor drainage of seven hours duration and ultrasound report with fetal
weight estimation of 4.4kg and a repeat ultrasound Scan at presentation showed
a fetal weight estimation of 5kg.
She was booked for emergency caesarean Section, two Units of whole
blood were provided, the anesthetist and the neonatologist were informed.
The outcome of the surgery was a live male neonate with good Apgar
score, the birth weight was 6.8kg, Birth length was 57cm, head circumference
was 36cm and umbilical cord length was 100cm. The baby was admitted at the
special baby Unit for 24 hours and thereafter discharges to the mother at the
lying in-ward to commence breast feeding. The patient was discharged after five
days. Both mother and baby are still doing well.
DISCUSSION
Fetal macrosomia is defined as the birth weight greater than 4000g
(4kg) or birth weight of 90thpercentile for the gestational age.(1)
The perinatal diagnosis of fetal
macrosomia could be by clinical estimation or through ultrasound. The clinical
methods of fetal weight estimation include Johnson’s method, Dawn’s method,
Dare’s method, Onan’s method, etc.(1,2) These clinical methods of fetal weight
estimation use the external measurement of the mother.(4,5) The advantages of
clinical method of fetal weight estimate are that they are simple, safe, cheap,
non invasive, convenient and they can be applied on poor resource settings
where ultrasound is not available.(1,2)
The demerits of clinical methods
of fetal weight estimation are that they depend on the clinical skill of the
clinician, results are notreproducible and intra-observer and inter-observer
errors are common.(2,3) Consensus has not been reached amongst various methods
of clinical methods of estimating fetal weight and this could have helped to
improve on the reproducibility and reliability of the results.(4)
Both clinical and ultrasound
method of fetal weight estimation are not predictable, in our index patient,
ultrasound estimation was 4.4kg, whereas the actual weight at birth was 6.8kg.Some
studies showed that ultrasound estimation of the fetal weight is a better
predictor of the actual birth weight. While other studies showed that the
reliability of ultrasound estimation of fetal weight to detect large babies is
poor, as it is observed on our index patient, the study went further to state
that ultrasound measurement has the tendency to over-estimate the weight of
small babies while underestimating the weight of large babies of diabetics
mellitus, (13) hence such objective measurement of suspected fetal macrosomia
should be handled with caution as this may lead to unnecessary obstetrics
interventions. (12,13) Therefore it is important to correlate ultrasound
estimation of fetal weight with the clinical estimation.(13) It has also been
reported in some literatures that some clinical methods of fetal weight
estimation have been shown to be as accurate as the ultrasonographic estimation
especially in poor resource setting where ultrasound is not available.(14)
The risk factors for fetal macrosomia
include obesity, over weight, multiparity, history of previous macrosomia,
diabetics mellitus, gestational diabetics, male sex and excessive weight gain
in pregnancy.(14)
However, our index patient is a
primigravida and she is over-weight evidenced by the body mass index of 27kg/m2,
the patient was not confirmed to have gestational diabetics, she had no family
history of diabetic mellitus. It is possible that the macrosomia may be due to
post term as the baby was delivered at the gestational age of 42 weeks. Since
she had glycosuria in index pregnancy, it is also possible that the macrosomia
may be due to glucose mediated. The sex of the baby delivered is male, is it
possible that male sex may have correlation with the weight of the baby,
however some studies have shown that there is a correlation between the fetal
weight and sex.(15) The umbilical cord length of the baby was 100cm and the sex
of the baby was male. This case report may be supporting the studies which
stated the fetal umbilical cord length has correlation with birth weight and
sex of a baby.(16) The complications associated with fetal macrosomia could be
maternal or fetal.(1,2) The maternal complications include dysfunctional
uterine extraction, prolonged labour, uterine rupture, increase risk for
caesarean section, spontaneous symphysiotomy, lower genital tract laceration
and Obstetric neuropathy.(8,9) Most of these complications were averted by
booking the patient for emergency caesarean section. This goes to support that
fetal macrosomia is associated with high
incidence of caesarean section (15-18).
The fetal complications include
shoulder dystocia, birth trauma and electrolyte Imbalance especially
hypoglycemia.(15,16) The baby delivered by our index patient had hypoglycaemis
shortly after delivery and this was corrected at the special case baby Unit.
The prevalence of fetal
macrosomia varies in sub-Sahara Africa and in Nigeria, the prevalence is as
high as 14.6%. ((5) This is a serious medical concern and the increasing
incidence of fetal macrosomiaim poses a great burden to health
facilities.(14-16) Therefore the knowledge of risk factors for fetal macrosomia
and conducting preconceptional care for the women at risk will reduce the
prevalence of fetal macrosomia and other attendant complications.(5-7)
CONCLUSION
Fetal macrosomia is an important cause of maternal and perinatal
morbidities. It imposes a great burden to health facilities. Fetal weight
estimation perinatally cannot be predicted accurately with either by ultrasound
or clinical method, though ultrasound
estimation of fetal weight is a better predictor of fetal weight but
correlating ultrasound estimation with clinical estimation could prevent
unnecessary Obstetrics intervention. Health workers in poor resource setting
should be trained on the clinical methods of fetal weight estimation to prevent
complications associated with fetal macrosomia.
Researchers should be explore scientific approaches in fetal
weight estimation by clinical methods
should work towards a consensus to improve on the reliability and
reproducibility of the formulae, taking into some of the draw backs using
ultrasound. This will prevent complications of fetal macrosomia in poor
resource settings.
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