Archives of Perinatal Medicine 15(2), 101-105, 2009
ORIGINAL PAPER
Hemoglobin and hematocrit concentrations influence
birth outcome in pregnant Polish adolescents
MAGDALENA RYCEL1,2, WOJCIECH SOBALA3, JAN WILCZYŃSKI1, DOROTA NOWAKOWSKA1
Abstract
Objectives: With regard to the decreasing number of young mothers who give birth in Poland we decided to
analyze retrospectively the relationship between hemoglobin and hematocrit concentration in 347 pregnant
women aged 15-25 years treated in the DFMMG PMMHRI in Łódź in the period between 2000 and 2006. The
study population was arranged into two groups: the research group of 111 pregnancies in the age between 15
and 18 and the control group of 236 adult women (19-25 yrs old). In the analysis we took into account:
obstetric history, hemoglobin and hematocrit concentration, prevalence of anemia. Results: In the group of
teenagers we observed a decreasing trend in number of deliveries. This trend occurred to be statistically
significant. The prevalence of anemia in adolescents during pregnancy was higher than typically reported in
adult women. In teenagers 11.97 g/dl, in control group 12.22 g/dl, the statistical difference was found
significant (p = 0.033). Conclusions: 1) The prevalence of anemia in multiple regression analyses occurred
higher in group of adolescents than in group of adult women before and after delivery. Differences in level of
Hg in bought group after delivery was statistically important. 2) Inadequate prenatal care, history of selfreported cigarette use were significantly associated with lower hemoglobin during pregnancy
Key words: adolescents, pregnancy, hemoglobin, hematocrit
Introduction
With regard to the process of decreasing age of sexual initiation in Poland among young women, becoming
pregnant and first birth, the problem of adolescent
pregnancy and motherhood appears to become a serious
social issue.
Currently the percentage of teenagers giving birth
between the age of 14 and 19 is 7% of the birthrate in
Poland. Between 2000 and 2007 a distinct decreasing
trend concerning pregnancies and births of juvenile Poles was observed [1]. Such assumption was confirmed by
results of analysis conducted by the Polish Ministry of
Health from 1985 to 2004 concerning number of teenage women giving birth [1]. As an example, an absolute
number of births given by teenage women in Poland in
1990 was as high as 44 thousand, in 2000 dropped down
to 27 thousand while in 2004 was only a little over 20
thousand.
American research shows that about most of adolescent pregnancies are unplanned and only few are wanted.
Among the most common causes of unplanned and premature motherhood, is lack of detailed knowledge about
1
contraceptives as well as limited access and no funds for
contraceptives. According to literature, about 26% of
girls and 30% of boys, as the main source of information
gives their peer group. The media is the only source of
knowledge for about 26% of young people. Low social,
economical and professional status is also significant in
this matter.
Adolescent pregnancies are an important issue of
contemporary perinatology. These pregnancies are burdened with a high risk of complications and they should
always be treated very carefully. Among them abortion,
premature birth, hypertension, low birth weight, and
three times higher perinatal mortality are regarded as
related to the young age of the mothers [2]. It is suggested that because of hypogenitalism and especially
uterine hypoplasia, the age of 15 yrs is considered to be
the critical point below which the perinatal mortality of
newborns increases. Moreover, because of unfinished
physical development and often occurring labor disproportion in adolescent patients, the percentage of caesarean sections within this group constitutes about 30%
of all births.
Department of Fetal-Maternal Medicine and Gynecology (DFMMG), Polish Mother’s Memorial Hospital Research Institute
(PMMHRI), Łódź, Poland
2
DFMMG, III Faculty of Obstetrics and Gynecology, MU, Łódź, Poland
3
Department of Environmental Epidemiology, Nofer Institute of Occupational Medicine, Łódź, Poland
102
M. Rycel, W. Sobala, J. Wilczyński, D. Nowakowska
In addition to the fact that problem of relationship
between hemoglobin and birth outcomes have not been
well characterized in Polish adolescents, despite the fact
that this group is at high risk of early childbearing, we
decided to examine the association of maternal hemoglobin level during pregnancy and after birth. We were
specifically interested in effects associated with low and
high maternal hemoglobin levels.
The aims of the study were: 1) to describe the frequency of delivery in adolescents in DFMMG PMMHRI
in Lodz in the period between 2000 and 2007; 2) to analyze the complications and outcome of pregnancy in Polish women giving birth before the age of 19; 3) to examine the difference in hematological markers (hemoglobin and hematocrit) in adolescent pregnancies in comparison to adults.
Material and methods
The data used in this analysis came from the registry of the DFMMG in the RIPMMH in Łódź (Poland)
during the period between 2000 and 2006. Study population included 347 women aged 15-25 years. They were
arranged into two groups: 15-18 years (n = 110) as the
research group and 19-25 years (n = 235) as the reference one. Pregnant women were selected by stratified random sampling technique.
We took into account the average age of women giving birth and the frequency of deliveries in adolescents
in the period 2000-2007 in PMMHRI. The measures of
birth presented here are the standard ones. Rates are
calculated as the number of events (birth) per 1000 women aged 15-18 per year. Reflecting date availability, age
of the adolescents was measured as age at outcomes, not
age at conception.
Separately we analyzed the hematological parameters in the mothers, both adolescent and controls, before
delivery and right after. During pregnancy the highest
level of hemoglobin concentration (Hb) and hematocrit
(Hct) is observed between 12th and 28th week then these
values decrease until the day of delivery. Anemia was
defined using the criteria for anemia during pregnancy.
With this criteria the concentration of Hb used to define
anemia was 11 g/dl and the level of Hct was 33% [3].
Statistical methods
We use two sided tests and significance level 0.05
for statistical inferences. We assessed time trend for
rates in adolescent pregnancies over years using Poisson
regression with identity link and population size as offset. We used linear regression to compare Hb and Hct
levels between age groups. All statistical analyses were
performed using STATA 9.0 program.
Results
Out of 10 856 women giving birth between 2000 and
2006 in the DFMMG RIPMMH in Łódź (Poland) there
were 111 (1%) teenagers up to the age of 18. According
to our data collected in 2000, the population of women
after delivery was 1446 patients out of which 22 were
adolescent, in 2001 group of women after delivery consisted of 1332 patients among which 15 were adolescents, in 2002 the numbers were respectively 1237 and
17 were adolescents, in 2003: 1598 and 12 adolescents;
2004: 1774 and 18; 2005: 1692 and 11 teenagers; 2006:
1777 out of which 15 were below 18 years old (Fig. 1).
The birth rate among examined adolescents during the
period 2000-2006 was very low (15 deliveries per 1000
adolescents in 2000, 12 per 1000 in 2001, 13 per 1000
in 2002, 7 per 1000 in 2003, 10 per 1000 in 2004, 6 per
1000 in 2005 and 8 per 1000 in 2006. In this group
during this 7 years of observation we observed a decreasing trend in numbers of deliveries (Fig. 1) this
trend occurred to be statistically significant (p = 0.013).
Fig. 1. Trend in pregnancies among adolescent woman
< 18 yrs (per 1000 deliveries) in Łódź (Poland)
Considering examination of the Hb and Hct level as
a routine due to increasing risk of anemia during pregnancy and puerperium, an analysis regarding this subject
in case of adolescent women was also conducted (Table 1).
In the population of women under 18 anemia occurred more frequently both before pregnancy and after
the delivery in comparison to the reference group of
women aged 19-25 (Table 1). In case of adolescent women the hemoglobin level before the delivery was as
high as 11.97 (se = 0.17) and in the reference group
12.22 (se = 0.086), (p = 0.140). However, in values of
Hemoglobin and hematocrit concentrations influence birth outcome in pregnant Polish adolescents
103
Table 1. Hematological parameters in adolescent pregnancies and adults before and after delivery
Age #18
n = 102
Age 18-25
n = 232
p
Hb before delivery
12.0 (0.15)
12.2 (0.086)
0.140
Hb after delivery
10.3 (0.17)
10.7 (0.1)
0.033
Hematological parameters
Hct before delivery
34.7 (0.40)
36.3 (0.25)
< 0.001
Hct after delivery
31.5 (0.45)
32.36 (0.27)
0.096
0.350 (0.004)
0.337 (0.002)
0.003
Hb difference after delivery
!1.7 (0.19)
!1.5 (0.11)
0.43
Hct difference after delivery
!3.4 (0.45)
!4.0 (0.28)
0.25
Hb/Hct before delivery
n – number of woman, Hb hemoglobin concentration (g/dl)
Hct – hematocrit concentration (L/L)
in parentheses standard error of the mean
post term hemoglobin in teenagers 10.3 (se = 0.17) and
in control group 10.7 (se = 0.1) the statistical difference
was found significant (p = 0.033).
The level of Htc in case of teenagers was 34.7 (se =
0.40) before delivery and 31.5 (se = 0.45) after delivery
(Table 1). Analogically, 36.3 (se = 0.25) before and 32.36
(se = 0.27) after the delivery in case of women aged
18-25. The analysis of pre-delivery values of levels of hematocrit showed significant difference (p = 0.001) in
those two groups. Post-delivery hematocrit values did
not vary in teenagers and in adult women (p = 0.096).
The level of Hb/Hct before delivery was 0.350 (se =
0.004) in adolescents woman and 0.337 (se = 0.002) in
adult women (Table 1). The statistical difference was
significant (p = 0.003). However, the Hb and Hct difference after delivery was Hb = !1.7 (se = 0.19), Hct =
!3.43 (se = 0.45), (p = 0.43) in research group and Hb
= !1.6 (se = 0.11), Hct = !4.04 (se = 0.28), (p = 0.25) in
the reference group.
Comment
The group of adolescent mothers 18 is very diversed. It consists from both – girls from pathological
families, undernourished, abusing alcohol or drugs and
from families with high socio-economical status [4].
Regardless of the family background, in this age group
we often deal with unwanted pregnancies [5] in case of
unmarried women.
On the basis of conducted research and statistical
analysis, it can be stated that the pregnancy in women
under the age of 18 have a higher risk of medical complications [6, 7] involving mother and child. The incidents of low birth weight (< 2500 g) is more than
double the rate for adults, and the neonatal death rate
(within 28 days of birth) is almost three times higher [8].
The mortality rate for the mother [9], although low, is
twice that for adult pregnant woman [10]. Adolescent
pregnancy has been associated with other medical problems including poor maternal weight gain, prematurity
anemia and sexually transmitted diseases. Young adolescents mothers are more likely then other groups to
give birth to underweight infants.
Moreover, in case of teenage mothers, high level of
immaturity in social and psychological aspect can be
observed. Girls are often forced to be single mothers,
put their children in the care of grandparents or uncles.
They often give up their education and they are not capable of gaining financial stabilization for themselves or
their children. Lack of care and support, the ignorance
of contraceptive methods are the reasons why they often
become pregnant yet again.
Adolescent pregnancy is the problem with occurs in
all societies, but the level of teenage pregnancy and
childbearing varies from country to country
In the literature we have a lot of well documented
pattern of decline in the adolescent birthrate in the industrialized countries over the past 25 years [11]. As
well as in the other countries, it can be seen that the
number of pregnancies and deliveries of adolescent
Polish women decreases significantly (Fig. 1). It is confirmed by the results of statistic analysis conducted
between 1985 and 2004, considering the number of deliveries of teenagers in Poland, conducted by the Ministry of Health [1]. As an example, the total number of
births given by teenage mothers in 1990 was 44 thousand, in 2000 was 27 thousand and in 2004 only a little
over 20 thousand. Adolescent birth rates in 1990 in
Poland was 31.5 per 1000. A similar situation occurred
in Canada 25.6 per 1000, England and Wales 33.2 per
1000 [11].
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M. Rycel, W. Sobala, J. Wilczyński, D. Nowakowska
In addition, in the United States the rate among white
teenagers was one of the highest among the developed
countries 59.9 per 1000. The range in the birthrate
across industrialized countries is very wide for example
in Japan rate was reported very low 3.6 per 1000 [11].
Another important fact with we noticed during the
study are huge differences between birthrate among
teenagers 15-17 years old. In this group in most of the
countries (Australia, Canada, England and Wales) the
rate was low (about 9-10 per 1000). The birthrate among
older adolescents 18-19 years old was much higher (3549 per 1000) This situation can be connected with the
fact that the abortion ratio among younger girls was
higher in the majority of countries.
The general decreasing trend of motherhood in
teenagers was connected with number of factors likely
to have had a greater impact on adolescents. For example sexual education in schools, improved knowledge
about contraception [12]. Despite increasing use of
contraception by teenagers at the time of first intercourse 50% of adolescent pregnancies occur within the first
6 month of initial sexual intercourse [13].
Another important problem that is strictly related to
the birth outcomes in adolescent mothers is anemia and
hemoglobin and hematocrit concentrations [14]. In the
present paper we checked the relationship between anemia, level of hemoglobin and hematocrit during pregnancy in Polish adolescents. In the study we found that this
group had higher prevalence of anemia during and after
pregnancy and that these adolescents were at risk for several adverse birth outcomes. This differences were of
significant importance in our study. Despite the fact that
anemia is dangerous for young mothers it may also have
neonatal consequences, because severe maternal anemia
during pregnancy had been related to iron deficiency [15]
anemia [16] in cognitive development in later life [10].
According to the other, the level of hemoglobin
stays in connection with the birth weight of the child
[17]. The lower the value of Hb, the lower the birth
weight of the newborn. It is also connected with the placenta weight and the preterm deliveries, occurring more
often in case of women under the age of 18. This fact is
strictly bound with the part played by Hb in a human
organism, its capability of transferring and delivering the
oxygen. It was also found, that there is an indirect connection between low Hb and Htc values, insufficient prenatal care and iron supply as well as the low BMI in case
of children [18].
Many studies have indicated that anemia during
pregnancy is explained by iron deficiency [14]. Characte-
rization of anemia during pregnancy must take into
account the alterations that occur in red cell mass and
expansion of plasma volume during pregnancy. These
normal physiological processes cause an expected fall in
hemoglobin concentrations, and this decrease influences
the criteria used to define anemia during pregnancy.
Elevated hemoglobin concentrations during the second
and third trimesters may by due to high iron status and
is associated with poor reproductive outcomes [19].
Interestingly, clinical and epidemiological evidence
has revealed that high hemoglobin concentration may be
due to maternal complications such as pregnancy-induced
hypertension or pre-eclampsia which are causally associated with perinatal morbidity and mortality [20]. High
hemoglobin concentration, due to inadequate plasma volume expansion, may increase blood viscosity, which leads
to poor placenta blood flow and limiting fetal growth [20].
As the research shows, the highest level of Hb and
Hct were be observed between 12th and 28th week of the
pregnancy (Hb 12.5 g/dl, Hct 36%), then these values
decreased till the day of delivery – after 38 weeks (Hb
11 g/dl, Hct 33%) [18]. Next, after about 8-12 weeks, these values returned to the proper level observed before
the pregnancy (Hb 13 g/dl, Hct 39%) [3].
The results confirm our research, as the average
level of hemoglobin just before the delivery among the
research group oscillated around 11g/dl and Hct was a
little beyond the level of 33%.
Our results considering levels of Hb and Hct did not
differ from the results discussed in the literature. Probably it is due to the fact that increased blood loss in case
of adolescents during the delivery, may be caused by
problems such as lack of cooperation with the woman in
labor during applying dressing material onto labor
wounds. A fact worth noticing is that the difference between Hct values is much bigger in case of mature women. Most probably it is caused by the fact that adult women undergo increased blood loss during delivery as
a result of abnormal uterus muscles shrinkage and in some cases its anatomy. This is connected with multiparity
and multiple pregnancies occurring more often in this
group. Also, as our research show, lower birth weight of
children born by adolescent mothers is closely connected with decreased level of Hb and Hct in the pre-delivery period and therefore insufficient nutrition of girls
during pregnancy, childbirth and during breast feeding.
The analysis of proportion of Hb/Hct in research
group and control group is also interesting. During the
research, we indicated a statistical difference between
mature women and teenagers. In case of mature women
Hemoglobin and hematocrit concentrations influence birth outcome in pregnant Polish adolescents
the proportion was lower which is most probably caused
by greater blood flow which influence more frequent
occurrance of swelling in the last trimester of the pregnancy in case of control group.
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J
Dorota Nowakowska
Department of Infections and Fetal Therapy
III Faculty of Obstetrics and Gynecology
Medical University in Łódź
Str. Rzgowska 281/289, 93-338 Łódź, Poland
e-mail: dnowakowska@yahoo.com