Preterm birth and low birth weight among in vitro fertilization twins: A systematic review and meta-analyses
Received 10 February 2009; received in revised form 30 July 2009; accepted 16 September 2009. published online 05 October 2009.
Abstract
Objective
The objective of this systematic review and meta-analyses was to determine the risks of preterm birth (PTB) and low birth weight (LBW) in twins conceived through in vitro fertilization (IVF) or IVF/intracytoplasmic sperm injection (ICSI) compared to spontaneously-conceived twins after matching or controlling for at least maternal age.
Study design
The MOOSE guidelines for meta-analysis of observational studies were followed.
Search strategy
Medline and Embase were searched using comprehensive search strategies. Bibliographies of identified articles were reviewed.
Selection criteria
English language studies of twins conceived by IVF or IVF/ICSI, compared with spontaneously twins, that matched or controlled for at least maternal age.
Data collection and analysis
Two reviewers independently assessed titles, abstracts, articles and study quality and extracted data. Statistical analyses were performed using the Review Manager (RevMan 5.0) software using a random effects model. Dichotomous data were meta-analyzed using relative risks (RR) and continuous data with a weighted mean difference.
Results
Twelve studies were included which had a total of 4385 twins conceived after IVF or IVF/ICSI (one stillbirth was excluded) and 11,793 spontaneously-conceived twins. After matching or controlling for maternal age and often other factors, compared to spontaneously-conceived twins, IVF twins had increased risks of both our primary outcomes: PTB (RR 1.23, 95% CI 1.09, 1.41) and LBW (<2500g, RR 1.14, 95% CI 1.06, 1.22). They were at increased risk for PTB <32–33 weeks (RR 1.63, 95% CI 1.17, 2.27) although the risks of late PTB (32–36 weeks, RR 1.12, 95% CI 0.85, 1.47), very LBW (<1500g, RR 1.28, 95% CI 0.73, 2.24), extremely LBW (<1000g, RR 0.88, 0.04, 19.40), intrauterine growth restriction (RR 1.06, 95% CI 0.72, 1.55) and the difference in the duration of gestation (−0.5 weeks, 95% CI −1.2 weeks, 0.2 weeks) were not statistically significantly increased compared to spontaneously-conceived twins. IVF twins had significantly lower mean birth weights (−105g, 95% CI −204g, −3g).
Conclusions
IVF twins have small but significantly increased risks of PTB, LBW, and lower mean birth weight compared to spontaneously-conceived twins after matching or controlling for at least maternal age.
aDivision of Maternal-Fetal Medicine, Departments of Obstetrics & Gynecology, Diagnostic Imaging, and Clinical Epidemiology and Biostatistics, McMaster University, 1200 Main St. West, HSC 3N52B, Hamilton, ON L8N 3Z5, Canada
bDepartment of Obstetrics and Gynecology, First Affiliated Hospital of Xi’an Jiao Tong University, Shaanxi Province, PR China
cFaculty of Health Sciences, McMaster University, Hamilton, Canada
dDepartment of Paediatrics, and Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada
eDepartment of Obstetrics and Gynecology, Mount Sinai Hospital and the University of Toronto, Toronto, Ontario, Canada
fProgram in Population Health Sciences, Hospital for Sick Children and the University of Toronto, Toronto, Ontario, Canada
1 Members of Knowledge Synthesis Group on determinants of low birth weight/preterm birth:
Prakesh Shah: Assistant Professor, Department of Paediatrics, Mount Sinai Hospital and Department of Health Policy, Management and Evaluation, University of Toronto, Toronto, Canada
Arne Ohlsson: Professor Emeritus, Department of Paediatrics, Mount Sinai Hospital and Departments of Paediatrics, Obstetrics and Gynaecology, and Health Policy, Management and Evaluation, University of Toronto, Canada
Vibhuti Shah: Associate Professor, Department of Paediatrics, Mount Sinai Hospital and Department of Health Policy, Management and Evaluation, University of Toronto, Toronto, Canada
Kellie E Murphy: Associate Professor, Department of Obstetrics and Gynecology, Mount Sinai Hospital and University of Toronto, Canada
Sarah D McDonald: Assistant Professor, Division of Maternal-Fetal Medicine, Departments of Obstetrics & Gynecology and Diagnostic Imaging, and Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Canada
Eileen Hutton: Associate Professor, Department of Obstetrics and Gynecology, McMaster University, Hamilton, Canada
Christine Newburn-Cook: Associate Professor & Associate Dean Research, Faculty of Nursing, University of Alberta, Edmonton, Canada
Corine Frick: Director, Alberta Perinatal Health Program and Adjunct Professor, Faculty of Nursing, University of Calgary, Calgary, Canada
Fran Scott: Associate Professor, Dalla Lana School of Public Health, University of Toronto and Toronto Public Health, Toronto, Canada
Victoria Allen: Associate Professor, Department of Obstetrics and Gynaecology, Dalhousie University, Halifax, Canada
Joseph Beyene: Assistant Professor, Research Institute of The Hospital for Sick Children and Dalla Lana School of Public Health, University of Toronto, Toronto, Canada.
ABSTRACT