Key words
German Perinatal Survey - smoking - maternal age - obesity - delivery statistics
Schlüsselwörter
Deutsche Perinatalerhebung - Rauchen - mütterliches Alter - Adipositas - Geburtenstatistik
Introduction
The German Perinatal Survey is routinely conducted in all of Germany. It offers the
opportunity to analyse temporal trends in maternal and neonatal characteristics by
comparing data from different years. We have previously presented analyses of data
from the Perinatal Survey for the years 1995–1997 [1], [2]. We have now analysed data from the
years 2007–2011. In this paper we present our analysis of the maternal
characteristics “age”, “body mass index” (BMI), and “smoking”, and compare these
data with the previous data from the 1990s. Neonatal characteristics and duration
of
pregnancy will be examined in a separate publication.
Material and Methods
The data analysed in the present report were obtained from the routine data
collection undertaken by the German Perinatal Survey, a mandatory survey that is
conducted throughout Germany. For the years 1995–1997, one of us, Manfred Voigt, was
kindly provided with data on 1 815 318 singleton pregnancies by the Chambers of
Physicians of all the states of Germany except Baden-Württemberg. These data were
collected into a database and analysed. For the years 2007–2011, data from the
German Perinatal Survey were provided to another one of our group, Rembrandt Scholz,
by the AQUA Institute (AQUA-Institut für angewandte Qualitätsförderung und Forschung
im Gesundheitswesen) in Göttingen, Germany; data on 3 187 920 singleton pregnancies
from all the states of Germany including Baden-Württemberg were analysed.
Statistical analysis was done using the SPSS computer programme. To minimise the
effects of data entry errors, plausibility checks were performed on the data;
implausible values were excluded from the analysis.
Results
Between 2007 and 2011, a total of 3 302 061 births were recorded in the German
Perinatal Survey. The majority (3 187 920) of these were singleton births; these
singleton pregnancies are investigated in the present report. Multiple births
accounted for less than 4 % of total births in each year ([Table 1]).
Table 1 Singleton and multiple births in Germany
2 007–2 011.
|
2007
|
2008
|
2009
|
2010
|
2011
|
Total
|
|
n
|
%
|
n
|
%
|
n
|
%
|
n
|
%
|
n
|
%
|
n
|
|
Singletons
|
647 394
|
96.7
|
647 136
|
96.7
|
627 542
|
96.5
|
638 337
|
96.4
|
627 511
|
96.5
|
3 187 920
|
|
Twins
|
21 258
|
3.2
|
21 562
|
3.2
|
21 944
|
3.4
|
23 192
|
3.5
|
22 357
|
3.4
|
110 313
|
|
Triplets
|
692
|
0.1
|
768
|
0.1
|
728
|
0.1
|
795
|
0.1
|
707
|
0.1
|
3 690
|
|
Quadruplets
|
20
|
|
22
|
|
33
|
|
28
|
|
22
|
|
125
|
|
Quintuplets
|
0
|
|
0
|
|
0
|
|
5
|
|
0
|
|
5
|
|
Sextuplets
|
2
|
|
6
|
|
0
|
|
0
|
|
0
|
|
8
|
|
Total
|
669 366
|
100.0
|
669 494
|
100.0
|
650 247
|
100.0
|
662 357
|
100.0
|
650 597
|
100.0
|
3 302 061
|
Mean maternal age (calculated as the year of the infantʼs birth minus the year of
the
motherʼs birth) has increased over the years, from 28.7 years in 1995 to 30.2 years
in 2011. The distributions of maternal age in 1995 and in 2011 show that in 2011,
there were more older mothers and fewer younger mothers compared to 1995 ([Fig. 1]).
Fig. 1 Maternal age (calculated as the year of the infantʼs birth minus
the year of the motherʼs birth). The distributions for maternal age and the
contributing case numbers (n) for the years 1995 and 2011 are shown as well as
the mean maternal ages for each year from 1995 to 1997 and from 2007 to
2011.
We observed a decrease in the number of women smoking. The German Perinatal Survey
collects data on maternal smoking after the pregnancy is known; however, in many
cases this information is missing (49.0 % of all cases in the 1995–1997 dataset had
no data on maternal smoking, and 20.2 % of all cases in the 2007–2011 dataset lacked
this information). When only the cases with data on smoking were analysed, 23.5 %
of
women were smokers in the 1995–1997 period compared to 11.2 % of women in the period
from 2007–2011.
Maternal BMI at the first obstetric consultation has also changed over time ([Fig. 2]). While the percentage of underweight women has
remained roughly constant at around 4 %, there has been a notable increase in
overweight, obese and morbidly obese women, and a corresponding drop in the
percentage of women with normal weight. Obese women with a BMI between 30 and
40 kg/m2 accounted for 8.2 % of all pregnant women investigated in
1995 and 13.0 % in 2011. In 1995, 0.6 % of women were morbidly obese (BMI
≥ 40 kg/m2); in 2011, 1.8 % of women were in this BMI category, a
three-fold increase. Mean maternal body weight (at the time of the first obstetric
consultation) has also increased over time from 65.9 kg in 1995, 66.3 kg in 1996 and
66.8 kg in 1997 to 67.8 kg in 2007, 68.1 kg in 2008, 68.3 kg in 2009, 68.6 kg in
2010 and 68.7 kg in 2011.
Fig. 2 Maternal body mass index (BMI, in kg/m2) at the first
obstetric consultation. The percentages of women within the BMI ranges are shown
for each year; case numbers are displayed at the top of the columns.
[Table 2] shows the maternal characteristics for the
different states of Germany for the years 2007–2011. Because the state of North
Rhine-Westphalia has two Chambers of Physicians collecting perinatal data,
“Westfalen-Lippe” and “Nordrhein”, there are two entries for North Rhine-Westphalia
in the table. Mean maternal age ranged from 28.3 years (Saxony-Anhalt) to 31.3 years
(Hamburg). The percentage of obese pregnant women was lowest in Berlin (10.4 %) and
highest in the Saarland (17.0 %). Mean maternal height was greater in the northern
states of Germany (more than 167 cm in Schleswig-Holstein, Mecklenburg-Western
Pomerania, Lower Saxony, and Hamburg) compared to the states further south.
Table 2 Maternal characteristics in the different states of
Germany 2007–2011 (singleton pregnancies). There are 17 entries for the
16 states of Germany because one state, North Rhine-Westphalia, has two
Chambers of Physicians collecting perinatal data, “Westfalen-Lippe” and
“Nordrhein”. Weight, height, and body mass index (BMI) are from the time
of the first obstetric consultation. The states of Germany/Chambers of
Physicians are presented in order of mean maternal height; n –
contributing case numbers.
|
State of Germany
|
Age (years)
|
Weight (kg)
|
Height (cm)
|
BMI ≥ 30 (%)
|
n
|
|
Schleswig-Holstein
|
29.9
|
70.8
|
167.8
|
16.8
|
96 193
|
|
Mecklenburg-Western Pomerania
|
28.4
|
68.9
|
167.5
|
14.4
|
60 728
|
|
Lower Saxony
|
29.9
|
70.3
|
167.5
|
16.5
|
288 627
|
|
Hamburg
|
31.3
|
67.2
|
167.4
|
11.2
|
96 046
|
|
Brandenburg
|
28.7
|
67.9
|
166.9
|
13.7
|
72 042
|
|
Bremen
|
30.0
|
69.5
|
166.9
|
15.9
|
37 967
|
|
North Rhine-Westphalia (1)
Chamber of Physicians
Westfalen-Lippe
|
29.7
|
69.8
|
166.9
|
16.3
|
317 510
|
|
Saxony
|
29.0
|
66.9
|
166.8
|
11.5
|
165 655
|
|
Berlin
|
30.1
|
66.0
|
166.7
|
10.4
|
163 756
|
|
Bavaria
|
30.5
|
67.2
|
166.7
|
12.2
|
497 418
|
|
Thuringia
|
28.6
|
67.7
|
166.7
|
13.4
|
74 461
|
|
North Rhine-Westphalia (2)
Chamber of Physicians
Nordrhein
|
30.3
|
68.8
|
166.6
|
15.1
|
380 059
|
|
Saxony-Anhalt
|
28.3
|
68.2
|
166.6
|
14.8
|
81 157
|
|
Hesse
|
30.5
|
68.1
|
166.5
|
13.9
|
236 892
|
|
Rhineland-Palatinate
|
29.8
|
69.0
|
166.4
|
16.1
|
150 196
|
|
Baden-Württemberg
|
30.6
|
67.4
|
166.3
|
13.0
|
433 144
|
|
Saarland
|
29.6
|
68.7
|
165.7
|
17.0
|
36 069
|
|
Total
|
30.0
|
68.3
|
166.8
|
14.0
|
3 187 920
|
Discussion
The comparison of data collected by the German Perinatal Survey for the years
1995–1997 and 2007–2011 allows temporal trends in maternal characteristics to be
identified. Important trends include increasing mean maternal age, a decreasing
percentage of smoking women, and an increasing percentage of overweight, obese, and,
especially, morbidly obese women. We describe a decrease in the numbers of smoking
women over time, although this finding has to be interpreted with caution due to the
high percentage of cases which lacked any data on maternal smoking. It should be
noted, however, that a similar trend of decreasing numbers of women smoking, albeit
somewhat less pronounced, has also been described elsewhere. Göhlmann and Schmidt
[3] reported a decrease in smoking rates among women
in two relevant age groups, 25–29 years and 30–34 years, when comparing micro census
data from the German Federal Statistical Office for the years 1995, 1999 and 2003,
although smoking rates were still in excess of 30 %. The 2005 and 2009 micro
censuses showed a further decline in the rate of smokers for women aged 30–34 years
to 29 and 28 %, respectively [4], [5]. The differences in the rates of smoking women between the German
Perinatal Survey data and the German Federal Statistical Office micro census data
may have been because in the former survey pregnant women were asked about their
smoking after their pregnancies became known; rates of smokers can be expected to
be
lower compared to the overall rate for all women (whether pregnant or not). While
the decrease in smoking women over time is clearly a positive development,
increasing maternal age and obesity rates present challenges in clinical practice.
Smoking has been linked to a number of adverse perinatal outcomes, some of which
have been reported in analyses of the German Perinatal Survey [6], [7], [8], [9], [10], although hypertensive
disorders of pregnancy seem to occur less commonly in smokers [11]. The risks associated with maternal obesity have also been described
[8], [9], [12], [13]. Finally, it has been
shown that late motherhood is associated with perinatal risks [14], [15].
A comparison of the states of Germany revealed inter alia that maternal height tended
to be higher in the northern States of Germany. This difference was also noted in
our previous analysis of data from the German Perinatal Survey [2].
Some limitations of our approach need to be discussed. Errors in data entry are
always a concern and indeed, some values in the datasets of the German Perinatal
Survey were implausible. We aimed to deal with data entry errors by excluding
implausible values from our analysis but we have no way of detecting data entry
errors that are not obviously implausible. However, it seems unlikely that this
should introduce a systematic bias. Another limitation concerns differences in how
data were handled in the two time periods and the completeness of the data. For
1995–1997, one of our group, Manfred Voigt, was provided with the data of the German
Perinatal Survey by the Chambers of Physicians of all the states of Germany except
Baden-Württemberg. For the years 2007–2011, another of our group, Rembrandt Scholz,
was given access to the data for all the states of Germany including
Baden-Württemberg by the AQUA Institute. Not having the data for one of the states
of Germany for the period of time 1995–1997 as well as the different ways in which
data were analysed are potential sources of error. Comparisons between the two
periods of time need to be interpreted with these limitations in mind. Finally, as
with all survey data reported by participants which has not been objectively
verified, there is the potential for deliberate misinformation on the part of the
participants themselves, especially with regard to answers to questions on unhealthy
lifestyles, such as smoking during pregnancy. This may also have contributed in the
large percentage of missing data for this question. As mentioned above, our data on
smoking during pregnancy should therefore be interpreted with caution.
Acknowledgements
We would like to thank the Chambers of Physicians of the states of Germany for
contributing perinatal data for the years 1995–1997 and we thank the AQUA Institute
for allowing us access to their data. We are grateful to Christel Fernow for help
in
preparing the figures and tables.
