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COMPARISON OF TWINNING RATES FOR VILLAGES IN
MAKARSKA REGION, CROATIA

JADRANKA SUNDE, MATIJA BORIĆ, NATALIJA URLIĆ and LARA URLIĆ

Journal of Biosocial Science / FirstView Article / December 2013, pp 1 - 12
DOI: 10.1017/S0021932013000011, Published online: 15 February 2013

Link to this article:

http://journals.cambridge.org/abstract_S0021932013000011

How to cite this article:
JADRANKA SUNDE, MATIJA BORIĆ, NATALIJA URLIĆ and LARA URLIĆ COMPARISON OF
TWINNING RATES FOR VILLAGES IN MAKARSKA REGION, CROATIA. Journal of Biosocial
Science, Available on CJO 2013 doi:10.1017/S0021932013000011

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J. Biosoc. Sci., page 1 of 12, 6 Cambridge University Press, 2013
doi:10.1017/S0021932013000011

C O M P A R I S O N O F T W I N N I N G R A T E S F O R

V I L L A G E S I N M A K A R S K A R E G I O N , C R O A T I A

JADRANKA SUNDE*

1

, MATIJA BORIC

´ †, NATALIJA URLIC´‡ and

LARA URLIC

´ ‡

*School of Electrical and Information Engineering, University of South Australia,

Mawson Lakes, Australia, †Faculty of Medicine, University of Split, Croatia and

‡Geni.com

Summary. A detailed database on the genealogy of the Makarska region in
Croatia has been created. The twinning rate for three villages in the region
(Podgora, Tucˇepi and Brela) were analysed over the period 1870 to 1940 and
factors such as mother’s age and birth order are discussed. Of the three villages,
Podgora was identified as having the highest twinning rate and consequently
records for Podgora were examined further to include almost 400 years of
historical data (from 1621 to 1950).

Introduction

The prevalence of increased twin births in Podgora compared with other places in the
Makarska region of Croatia has been suspected. This study undertook to check this
notion in an objective manner by: (1) comparing records for Podgora with records
from other villages in the same area and choosing a period for which well preserved
records exist; (2) examining and reviewing studies on twinning rates for other countries
and defining the parameters to observe; (3) comparing twinning rates for the chosen
villages including analysis of mother’s age and birth order; and (4) examining further
incidence of twin births using all available records for Podgora.

This work should shed light on the current popular belief that the incidence of twin

births in Podgora is higher than expected, and higher than in surrounding villages of
the same regions.

Comparison period

Communities with well documented ancestry represent invaluable tools for different
demographic studies. The Makarska region of Croatia (Makarsko primorje, see Fig. 1)
stretches 50 km south-east of Split, between the towns of Brela and Gradac. In this
analysis data for Podgora, Tucˇepi and Brela were included as their current population

1

1

Corresponding author. Email: [e-mail]

levels are similar, i.e. between 1700 and 2000 people for each village. While for Tucˇepi
(which consists of a single village) and Brela (which consists of two settlements: Brela
Gornja and Brela Donja) all records are included, for Podgora (which consists of five
smaller settlements), only records for two settlements, Podgora and Drasˇnice, are included.

The documents used for the analysis are kept in the State Archives of Zagreb,

Zadar and Split, the Archbishop Archive in Split, the Registry Office in Makarska
and the church offices in Podgora, Drasˇnice and Brela. They contain the following:

Podgora (settlement): births 1621–1948, marriages 1621–1949, deaths 1732–1952
Drasˇnice: births 1736–1993, marriages 1739–1993, deaths 1670–1993
Tucˇepi: births 1667–2000, marriages 1731–2000, deaths 1772–2000
Gornja Brela: births 1862–1993, marriages 1858–1993, deaths 1862–1993
Donja Brela: births 1825–1993, marriages 1825–1993, deaths 1841–1993

Figure 2 summarizes the records available and indicates the period (1870–1940) for

which comparison is drawn. In the Appendix, a detailed description of the historical
documents and their locations is given. Apart from birth, marriage and death records,
census data were available for certain periods, and also contributions from numerous
families to cover the periods up to today. In Table 1 the lengths of time (in years) for
which records were available are specified, as well as the available census data for

Fig. 1. Map of the Makarska region of Croatia with the villages of Podgora, Tucˇepi
and Brela marked.

J. Sunde et al.

2

each place. Other records used in the research include numerous books and articles
(Stojkovic´, 1933; Kaer, 1996; Ravlic´, 2000).

Factors affecting twin births

The twinning rate globally is estimated at about 10 twins per 1000 births (i.e. 1%), as
stated in Peller (2005), with an indication that this has changed significantly over the

*%UHOD0.8

*%UHOD0.9

*%UHOD0.5

'%UHOD0.9

'UDãQLFH0.5

7XþHSL0.5

7XþHSL0.9

7XþHSL0.8

'UDãQLFH0.9

3RGJRUD0.8

3RGJRUD0.9

3RGJRUD0.5

'%UHOD0.8

'UDãQLFH0.8

'%UHOD0.5

Fig. 2. Availability of records for each settlement used in the analysis, with the period
for which data are available for all areas marked with a box. MKR: Book of Births
(Maticˇna Knjiga Rodenih, in Croatian); MKV: Book of Marriages (Maticˇna Knjiga
vjencˇanih, in Croatian); MKU: Book of Deaths (Maticˇna Knjiga umrlih, in Croatian).

Table 1. Number of years of available records for each place, Makarska region,

Croatia

Place

Births

a

(number of

years)

Marriages

b

(number of

years)

Deaths

c

(number of

years)

Census (year)

Podgora

379

380

268

1839, 1857, 1910, 1920

Drasˇnice

257

254

320

1802, 1895, 18/19th c., 19/20th c., 1871

Tucˇepi

333

255

199

1695, 1802

Gornja Brela

131

135

131

1802, 1805

Donja Brela

131

161

152

1802, 1805, circa 1810, 1835, 1892, 1910

Sources:

a

MKR;

b

MKV;

c

MKU. See legend to Fig. 2 for definitions of abbreviations.

Twinning rates in Croatia

3

last 50 years. While twin maternities are nowadays more often used as a measure of
twinning rate (where twin births are counted as one; see, for example, Fellman &
Eriksson, 2002), in this study the previous definition has been adopted. Only the
twinning rate up to 1940 will be analysed, i.e. the period before fertility treatments
were introduced. Numerous studies have been conducted to assess twinning rates for
specific populations and define the parameters affecting it. Some of these studies con-
sidered to be relevant, where authors have attempted to quantify twinning rate and
the effect of mother’s age and to identity other factors possibly affecting it, have been
selected:

Using statistics on Australian births during the period 1944–63, Pollard (1969)

concluded that the proportion of multiple births increases with increasing mother’s
age until 37, and decreases thereafter, and that the proportion of multiple births
decreases after the first year of marriage.

A study on 1938 data for the USA by Enders & Stern (1948), looking at mother’s

age in the USA, concluded that twinning rate increases until 35–40 and sharply
decreases after 40–44.

A study by Pison & Couvert (2004), looking at the last three centuries in France,

has shown that twinning rate has varied from less than 1% to 2%, and that it is
affected by other factors, such as family behaviours, which are possibly affected
by global events.

A study by D’Addato et al. (2006) looked at twinning rates in fourteen European

countries, for the period between 1900 and 2000, and observed a peak just after the
end of World War I (WWI) in countries like Italy, France, Germany and Sweden.

The present study analyses twinning rate, mother’s age and birth order and will

attempt to define social factors that could have affected twinning rate.

Data analysis

To test if there is a higher incidence of twin births in Podgora, a period (1870–1940) for
which complete data were available was chosen. For each village the following infor-
mation was recorded: number of infants and twins born (including sex) in each year,
mother’s age and birth order.

Twinning rate comparison

The total number of infants born in each place, along with an overall percentage

of twins for each village during the comparison period, are shown in Table 2, where
number of twins born is included in total number of births. The numbers quoted refer
to number of infants born (a set of twins is counted as 2), where all births are recorded,
both live and stillborn (which are almost negligible). Additional information, such as
mortality of infants during the first year of life, was compared for twins and by sex,
but not included in this paper as no conclusions could be drawn. The percentage of
male infants born was also included.

It can be concluded that twinning rate for Podgora in a given period was con-

siderably higher at 2.3% than in the neighbouring villages of Tucˇepi (1.0 %) and Brela
(1.5 %).

J. Sunde et al.

4

Mother’s age and birth order

As seen in the literature (Enders & Stern, 1948; D’Addato et al., 2006), mother’s

age is considered an important factor in twinning rate. The present analysis correlates
well with other reported findings. Table 3 presents mean twins’ mother’s age for the
three villages (with standard deviation and median values).

Age distribution was also considered (Figs 3 and 4). The highest chance of having

twins was among women between the ages of 30 and 40, with a peak around 34 years
of age.

Birth order for each twin birth correlates well with the Australian study (Pollard,

1969), with multiple birth occurrence decreasing after the first year of marriage (first
birth), which possibly indicates that twin births occur more often when the first child
is born to a women over 30.

Social and family factors

Figure 5 shows the number of infants and twins born in the study villages over the

period 1870–1940. A marked dip in the number of infants born around the period
of WWI was observed, which is in good agreement with the findings of other studies
(Pison & Couvert, 2004; D’Addato et al., 2006). These authors attributed this to
changes in family behaviour as a consequence of the war and the economic situation.
Figure 6 and Table 4 show the data pooled into 5-year intervals.

Twinning rate for Podgora for period 1621–1950

A detailed study of infant birth and twinning rates was conducted on the Podgora

data for the period 1621–1950. While the analysis was conducted in the same way as
for the comparison of the three villages, i.e. including twinning rate, mother’s age and
birth order, only the results that were in some way unexpected will be discussed here.

Table 2. Infant births, twinning rates and proportion male births in different villages,

Makarska region, Croatia, 1870–1940

Infants born

Twins born

Twining rate (%)

Male infants

% male infants

Podgora

5682

128

2.3

2864

50.4

Tucˇepi

3475

36

1.0

1749

50.3

Brela

2756

42

1.5

1408

51.1

Table 3. Average age of the mothers of twins for each village, Makarska region,

Croatia, 1870–1940

Podgora

Tucˇepi

Brela

Average age (SD) (years)

31.3 (5.9)

32.5 (6.3)

37.2 (5.9)

Median

31

32

39

Twinning rates in Croatia

5

Figure 7 presents the information graphically. While the twinning rate stayed consis-
tently above 1.6%, five periods with slight irregularities were identified and examined
further (Table 5). An unusual proportion of male babies born was noticed during the
five-year period (1940–1950). The average age of women giving birth to twins corre-
lates well with other studies, with an average value for the whole period of 34 years
(SD 6, median 34). The possible reasons for this (based on Pavisˇic´ 1851; Bozic-Buzancic,
1996; Anusˇic´, 2008) are discussed below.

Period 1 (1820 to 1830). This followed a period of lower birth rate marked by

general turmoil in the area, with war, hunger and disease. It started in 1805 with the
fall of the area to France, which in 1807, as a punishment for rebellion against them,
burned down 117 houses. In 1813 Austria returned as ruler, and in the same year
the Black Death appeared in Herzegovina, and came across the Neretva Valley to the
Makarska region. More then 6000 people died in the Makarska region, with 40 families
disappearing altogether. After this epidemic, a period of hunger started, especially during

0RWKHUVDJH

Fig. 3. Percentage distribution of twins by mother’s age (with birth order indicated) for
Podgora, Tucˇepi and Brela combined, 1870–1940.

J. Sunde et al.

6

1816 and 1817. There were also volcano eruptions in Asia, resulting in months of heat,
mud, constant dust and red rain, destroying agriculture and causing a period of hunger
in the whole of Europe (as recorded by Pavisˇic´, 1851). After 1820, there was a gradual
increase in birth rate, with a sharp increase in twinning rate.

%LUWKRUGHU

Fig. 4. Percentage distribution of twins by birth order (with mother’s age indicated) for
Podgora, Tucˇepi and Brela combined, 1870–1940.

3RGJRUDERUQ
3RGJRUDWZLQ
7XþHSLERUQ
7XþHSLWZLQ
%UHODERUQ
%UHODWZLQ

Fig. 5. Number of infants and twins born in Podgora, Tucˇepi and Brela, 1870–1940.

Twinning rates in Croatia

7

Period 2 (1868–1885). A high twinning rate was recorded, while population growth

was steadily up. This was the peak period, just before WWI, as reflected in other places
around Dalmatia (see records for Blato), when many places recorded increases in popula-
tion, for example Blato on Korcˇula doubled its population.

3RGJRUDWZLQ
7XþHSLWZLQ
%UHODWZLQ

Fig. 6. Twins (percentage of all recorded births) born in Podgora, Tucˇepi and Brela,
1870–1940.

Table 4. Infants born, twinning rates and proportion of males born for each village,

Makarska region, Croatia, 1870–1940

Podgora

Tucˇepi

Brela

Infants

born

Twins

born

Twining

rate (%)

Infants

born

Twins

born

Twining

rate (%)

Infants

born

Twins

born

Twining

rate (%)

1871–1875

388

10

2.6

165

0

0.0

83

2

2.4

1876–1880

345

16

4.6

166

0

0.0

134

4

3.0

1881–1885

418

12

2.9

169

4

2.4

167

2

1.2

1886–1890

453

8

1.8

237

2

0.8

174

2

1.1

1891–1895

498

2

0.4

327

6

1.8

239

4

1.7

1896–1900

506

6

1.2

360

6

1.7

218

2

0.9

1901–1905

535

14

2.6

350

6

1.7

228

4

1.8

1906–1910

515

12

2.3

323

2

0.6

245

4

1.6

1911–1915

468

16

3.4

244

0

0.0

252

0

0.0

1916–1920

260

6

2.3

107

2

1.9

150

4

2.7

1921–1925

387

12

3.1

267

6

2.2

223

0

0.0

1926–1930

300

2

0.7

222

2

0.9

225

2

0.9

1931–1935

297

8

2.7

276

0

0.0

193

4

2.1

1936–1940

240

4

1.7

262

0

0.0

225

8

3.6

J. Sunde et al.

8

Period 3 (1910–1920). This is the period around WWI and is in accordance with

observations from Pison & Couvert (2004), who reported higher twinning rates for the
number of European countries.

Period 3 (1920–1940). This corresponds to the period between the two world wars.

Period 4 (1940–1950). This is the period around WWII and correlates well with the

observations of Pison & Couvert (2004). Figure 6 shows that since 1771, of all infants
born, the sex balance was maintained and was consistent at around 50%, except for the
interesting observation that the proportion of male infants born reached 89%.

Conclusions

From this comparison of three neighbouring Croatian villages (Podgora, Tucˇepi and
Brela) over the period 1870 to 1940, the following has been established:

WRWDOERUQ
WZLQVERUQ
WRWDOGLHG

Fig. 7. Infant and twin births for Podgora, 1621–1950.

Table 5. Infants born, twinning rates and proportion of males born for Podgora,

Makarska region, Croatia, 1621–1950

Time period

Infants

born

Twins

born

Twining

rate (%)

% males

Average

births/year

Period 1

1820–1830

337

20

5.9

47.8

67

Period 2

1868–1885

1013

32

3.2

50.3

60

Period 3

1910–1920

561

12

2.1

48.1

56

Period 4

1920–1940

977

22

2.3

50.6

49

Period 5

1940–1950

299

6

2.0

89.3

30

Total

10,860

214

2.0

51.3

33

Twinning rates in Croatia

9

The twinning rate of 2.3% for Podgora village is well above the generally expected

rate and well above the rates for neighbouring villages.

Mother’s age plays a significant role in the twinning rate, with the average age of

mothers giving birth to twins for the three villages ranging from 31.3 to 37.2 years.

Twins occur more often in first births and the rate gradually goes down with sub-

sequent births.

The number of infants born and twinning rate in the study region have varied

greatly throughout history, and this correlates well with the findings of other Euro-
pean studies.

Further, detailed analysis of records for Podgora covering the period from 1620 to

1950 reveal that the twinning rate for Podgora has consistently been high throughout
history, with peaks in specific periods. There is also a remarkable ratio of male vs
female infants born immediately after WWII with 89% of infants being male.

Future research will use the twin maternities measure, and possibly combine data

with those from other regions with a high incidence of twin maternities.

Acknowledgments

The authors are grateful to all those who helped check the records, especially Smiljana
Sunde, Lynette Matulovich, Noelene Erceg, Fred Petric, Ivica Domagoj Sunde, and
also to Geni, a platform that allowed us to work on this problem collaboratively.

References

Anusˇic´, N. (2008) Socijalna obiljezˇja smrtnosti u Makarskoj u drugoj polovici 19. stoljec´a [Social

implications of death rate in Makarska during second half of 19th century] (in Croatian). Radovi
Zavoda za hrvatsku povijest 40, 119–149.

Bozic-Buzancic, D. (1996) Glad, prosjaci, epidemije, higijenske i zdravstvene prilike u Dalamciji

krajem 18. I pocˇektom 19. st. [Hunger, beggars, hygiene and health situation in Dalmatia at the
end of 18th and 19th century] (in Croatian). Radovi Zavoda za hrvatsku povijest 29, 138–151.

D’Addato, A. V., Couvert, N. & Pison, G. (2006) Trends in the Frequency of Twin Births

Over the Last Century: European Comparisons. URL: epc2006.princeton.edu/download.aspx?
submissionId=60568 (accessed April 2012).

Enders, T. & Stern, C. (1948) The frequencies of twins, relative to age of mothers, in American

populations. Genetics 33(3), 263–272.

Fellman, J. & Eriksson, A. W. (2002). On the standardisation of the twinning rate. Twin Research 5,

19–29.

Jurisˇic´, K. (1984) Iz Makarske prosˇlosti [From Makarska’s history] (in Croatian). Franjevacˇki

samostan, Makarska.

Kaer, P. (1996) Makarska i Primorje [Makarska and its region] (in Croatian). Reprinted from

1914. Matice hrvatska, Makarska, Croatia.

Pavisˇic´, V. C. (1851) Uspomena povistna o kugi makarskoj god. 1815: pisana talianskim i

dalmatinskim-bosanskim jezikom/od opata Luigja Cesara Pavisˇic´a. – U Becˇu, 1851. [Memory
of Black Death in Dalmatia in 1915 written in Italian and Dalmatian–Bosnian language
from father Cesar, Vienna] (in Croatian).

Peller, S. (2005) A new rule for predicting the occurrence of multiple births. American Journal of

Physical Anthropology 4(1), 99–106.

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Pison, G. & Couvert, N. (2004) The frequency of twin births in France: the triple influence of

biology, medicine and family behaviour. Population 59(6), 765–794.

Pollard, G. N. (1969) Multiple births in Australia, 1944–63. Journal of Biosocial Science 1, 389–

404.

Ravlic´, J. (2000) Makarska i njezino Primorje, dopunjeno i i izmjenjeno izdanje [Makarska and its

region; updated version]. Ogranak Matice hrvatska, Makarska.

Stojkovic´, M. (1933) Podgora u 17. stoljec´u [Podgora during the 17th century] (in Croatian).

ZZNZ

ˇ IO, Knjiga XXIX, sv. I. Zagreb.

Appendix: detailed bibliography for archive documents

Podgora

Drzˇavni Arhiv (State Archive), Zagreb

MKR/MKV 1621–1636, 1637–1689

Drzˇavni Arhiv (State Archive), Zadar

MKR 1731–1794, 1795–1825, includes Census for 1826, 1828, 1832, 1830–1846
MKV 1731–1830, 1825–1841, 1841–1857
MKU 1732–1802, 1802–1830, 1825–1830, 1831–1854, mix MKR/MKV 1689–
1730

Drzˇavni Arhiv (State Archive), Split

MKR 1846–1863, 1863–1879, 1880–1911, 1911–1933, 1933–1948
MKV 1858–1897, 1897–1949
MKU 1854–1873, 1873–1903, 1903–1936, 1937–1949, 1946–1952

Nadbiskupski Arhiv (Archbishop Archive), Split

Census 1839, 1857

Zˇupni Ured (Church Office), Podgora

Census 1910, 1920

Drasˇnic

Drzˇavni Arhiv (State Archive), Zadar

MKR 1736–1796, 1796–1835, 1825–1863
MKV 1739–1834, 1837–1857
MKU 1670–1736, 1739–1834, 1825–1874

Drzˇavni Arhiv (State Archive), Split

MKR 1863–1889, 1889–1901
Census 18/19th c., 19/20th c., 1871

Nadbiskupski Arhiv (Archbishop Archive), Split

Census 1802

Maticˇni Ured (Registry Office), Makarska

MKR 1901–1948, 1946–1952, 1953–1958, 1959–1993
MKV 1858–1933, 1933–1946, 1946–1952, 1952–1958, 1960–1993
MKU 1874–1910, 1910–1946, 1946–1952, 1952–1958, 1959–1993

Zˇupni Ured (Church Office), Drasˇnice

Census 1895

Twinning rates in Croatia

11

Tucˇepi

Drzˇavni Arhiv (State Archive), Zadar

MKR 1667–1772, 1772–1801, 1802–1825, 1825–1830, 1830–1856
MKV 1731–1771, 1772–1825, 1839–1857
MKU 1772–1825, 1825–1837

Drzˇavni Arhiv (State Archive), Split

MKR 1856–1871, 1871–1897, 1897–1906
MKV 1858–1895
MKU 1864–1870, 1872–1909

Nadbiskupski Arhiv (Archbishop Archive), Split

Census 1802, 1695

Maticˇni Ured (Registry Office), Makarska

MKR 1906–1941, 1941–1949, 1946–1951, 1951–1952, 1953–1958, 1959–1967,
1959–1998, 1998–2003

Donja Brela

Drzˇavni Arhiv (State Archive), Zadar

MKR 1825–1835 (for both Gornja and Donja Brela)
MKV 1825–1850 (for both Gornja and Donja Brela)

Drzˇavni Arhiv (State Archive), Split

MKR 1872–1894, 1895–1907

Nadbiskupski Arhiv (Archbishop Archive), Split

Census 1802, 1805 (for both Gornja and Donja Brela)

Maticˇni Ured (Registry Office), Makarska

MKR 1908–1944, 1944–1948, 1946–1952, 1952–1958, 1959–1977, 1978–1993
MKV 1857–1929, 1930–1949, 1949–1952, 1952–1958, 1959–1977, 1978–1993
MKU 1841–1888, 1889–1935, 1935–1943, 1952–1958, 1958–1978, 1978–1993

Zˇupni Ured (Church Office), Brela

Census cc1810, cc1835, SA 1892, SA 1910

Gornja Brela

Drzˇavni Arhiv (State Archive), Split

MKR 1862–1903

Maticˇni Ured (Registry Office), Makarska

MKR 1904–1948, 1946–1952, 1952–1958, 1959–1993
MKV 1858–1946, 1946–1952, 1952–1958, 1959–1993
MKU 1962–1889, 1890–1949, 1949–1952, 1952–1958, 1959–1993

J. Sunde et al.

12