A prospective series of 90 consecutive pregnancies (70 singleton, 16 t
win and 4 triplet pregnancies) resulting in births of 114 infants afte
r in vitro fertilisation (IVF) at Rigshospitalet were compared to a co
ntrol group of pregnancies and deliveries in 70 non-IVF infertility pa
tients with singleton pregnancies and 20 women with normal fertility w
ith twin (n=16) or triplet (n=4) pregnancies. No differences in the in
cidence of third trimester pregnancy complications, abnormal Fetal kar
yotypes or malformations were found. The number of women with spontane
ous onset of labor and the gestational age at delivery were similar in
the IVF and control groups. In singleton deliveries, the birth weight
was lower (p<0.025) in the IVF group (median 3145 g, range 890-4300 g
) than in the control group (3399 g, 2592-4850 g), whereas in multiple
gestation similar birth weights were found in the IVF and control gro
ups. We conclude that the birth weight in singleton deliveries after I
VF is lower than the birth weight in infertility patients treated diff
erently. The cause of this difference remains obscure.