A longitudinal study of the insulin-like growth factor system before, during and after pregnancy in healthy women

• The maternal insulin-like growth factor (IGF)-system is considered to influence fetal growth. In this longitudinal study of 23 healthy women we aimed 1) to assess maternal serum levels of IGF-I, IGF-II, IGF binding protein (IGFBP)-1, IGFBP-3 and protease activity against IGFBP-3 before, during and after pregnancy, and 2) to relate these levels in early and late pregnancy to fetal and birth weight. Serum was collected before pregnancy, in weeks 8, 14, 20, 32 and 35 of pregnancy and 2 weeks postpartum. IGF-I, IGF-II, IGFBP-1, and IGFBP-3 were analyzed with radioimmuno/radiometric assays and protease activity with Western blot. Fetal weight was measured by means of ultrasound (week 31 of pregnancy) and birth weight was recorded. IGF-I was initially decreased during pregnancy, compared to before conception. This early decrease was not correlated with fetal or birth weight. In late pregnancy, IGF-I and protease activity were positively related to fetal weight, whereas from week 20 of pregnancy IGFBP-1 showed an inverse association with birth weight. We suggest that in healthy pregnant women there is a fine-tuned balance within the maternal IGF-system, with components With either promoting or restricting influences on fetal growth. The results indicate that maternal IGFBP-1 cguld be used from mid-pregnancy as a marker for birth weight.

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MEDICINE

MEDICIN

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