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A prospective study of twinning and perinatal mortality in urban Guinea-Bissau

Morten Bjerregaard-Andersen12*, Najaaraq Lund13, Frida Staarup Jepsen13, Luis Camala14, Margarida Alfredo Gomes14, Kaare Christensen567, Lene Christiansen57, Dorte Møller Jensen8, Peter Aaby13, Henning Beck-Nielsen8, Christine Stabell Benn13 and Morten Sodemann12

Author Affiliations

1 Bandim Health Project, INDEPTH Network, Apartado 861, 1004, Bissau Codex, Guinea-Bissau

2 Department of Infectious Diseases, Odense University Hospital, Sdr. Boulevard 29, 5000, Odense C, Denmark

3 Research Center for Vitamins and Vaccines (CVIVA), Statens Serum Institute, Artillerivej 5, 2300, Copenhagen S, Denmark

4 Department of Maternity, National Hospital Simão Mendes, Bissau, Guinea-Bissau

5 The Danish Twin Registry, Epidemiology, Institute of Public Health, University of Southern Denmark, J.B. Winsløwsvej 9, 5000, Odense C, Denmark

6 Department of Clinical Biochemistry and Pharmacology, Odense University Hospital, Sdr. Boulevard 29, 5000, Odense C, Denmark

7 Department of Clinical Genetics, Odense University Hospital, Sdr. Boulevard 29, 5000, Odense C, Denmark

8 Department of Endocrinology, Odense University Hospital, Kløvervænget 6, 5000, Odense C, Denmark

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BMC Pregnancy and Childbirth 2012, 12:140  doi:10.1186/1471-2393-12-140

Published: 5 December 2012



Despite twinning being common in Africa, few prospective twin studies have been conducted. We studied twinning rate, perinatal mortality and the clinical characteristics of newborn twins in urban Guinea-Bissau.


The study was conducted at the Bandim Health Project (BHP), a health and demographic surveillance site in Bissau, the capital of Guinea-Bissau. The cohort included all newborn twins delivered at the National Hospital Simão Mendes and in the BHP study area during the period September 2009 to August 2011 as well as singleton controls from the BHP study area. Data regarding obstetric history and pregnancy were collected at the hospital. Live children were examined clinically. For a subset of twin pairs zygosity was established by using genetic markers.


Out of the 5262 births from mothers included in the BHP study area, 94 were twin births, i.e. a community twinning rate of 18/1000. The monozygotic rate was 3.4/1000. Perinatal mortality among twins vs. singletons was 218/1000 vs. 80/1000 (RR = 2.71, 95% CI: 1.93-3.80). Among the 13783 hospital births 388 were twin births (28/1000). The hospital perinatal twin mortality was 237/1000.

Birth weight < 2000g (RR = 4.24, CI: 2.39-7.51) and caesarean section (RR = 1.78, CI: 1.06-2.99) were significant risk factors for perinatal twin mortality. Male sex (RR = 1.38, CI: 0.97-1.96), unawareness of twin pregnancy (RR = 1.64, CI: 0.97-2.78) and high blood pressure during pregnancy (RR = 1.77, CI: 0.88-3.57) were borderline non-significant. Sixty-five percent (245/375) of the mothers who delivered at the hospital were unaware of their twin pregnancy.


Twins had a very high perinatal mortality, three-fold higher than singletons. A birth weight < 2000g was the strongest risk factor for perinatal death, and unrecognized twin pregnancy was common. Urgent interventions are needed to lower perinatal twin mortality in Guinea-Bissau.