The contribution of assisted conception, chorionicity and other risk factors to very low birthweight in a twin cohort.
OBJECTIVE
To investigate the contribution of assisted conception (assisted reproductive technology and ovulation induction), chorionicity and selected maternal risk factors for very low birthweight.


METHODS
Retrospective twin cohort study.


METHODS
Staff model Colorado Health Maintenance Organization.


METHODS
Five hundred and sixty-two twin gestations [assisted = 193 (34%); unassisted = 369 (66%)].


METHODS
Data were collected from a perinatal database and medical record review. Data were analysed using univariate and multivariable logistic regression analysis.


METHODS
Very low birthweight.


RESULTS
Women with assisted twin gestation were more likely to be older, nulliparous, non-smokers, married, have a prior history of a miscarriage and a dichorionic placentation. There was no difference in the distribution of low and very low birthweight, discordant growth or preterm delivery between assisted and unassisted twin gestations. Significant risk factors for very low birthweight were: a prior preterm birth (odds ratio, OR, 3.8, 95% confidence interval, CI, 2, 7), monochorionicity (OR 3, 95% CI 2, 4.7), nulliparity (OR 2, 95% CI 1.3, 3), cigarette smoking (OR 1.8, 95% CI 1, 3) and prior miscarriage (OR 1.6, 95% CI 1, 2). Monochorionicity was significantly associated with adverse perinatal outcomes.


CONCLUSIONS
Assisted conception did not play a significant role in the occurrence of very low birthweight in this cohort. A history of preterm birth and a monochorionic twin gestation were the leading risk factors for very low birthweight. Associated risk factors for very low birthweight were nulliparity, cigarette smoking and a prior miscarriage.
Lynch
Anne
A
Clinical Research Unit, Kaiser Permanente, Denver, Colorado, USA.
McDuffie
Robert
R
Stephens
Janet
J
Murphy
James
J
Faber
Kenneth
K
Orleans
Miriam
M
D000328:Adult; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D019102:Infant, Very Low Birth Weight; D016015:Logistic Models; D015999:Multivariate Analysis; D010298:Parity; D011247:Pregnancy; D011272:Pregnancy, Multiple; D027724:Reproductive Techniques, Assisted / Q000009:adverse effects*; D012189:Retrospective Studies; D012307:Risk Factors; D014427:Twins