Look at what Martha Christy  (Your Own Perfect Medecine p. 176) has to say about it:

"Although pregnant woman have been treated with successfully urine therapy for morning sickness or edema, the therapy should not be used during pregnancy without the supervision of a doctor familiar with the medical use of urine.

Doctors have reported that they have used urine therapy for morning sickness in pregnancy with excellent results, but there are reports of two spontaneous abortions which occurred after urine therapy treatments (Dunne and Plesch), possibly because of the natural release of toxins which occur with urine therapy."  http://naturinologie.info/ressources_amazon_en.htm#Perfect_medecine

Amniotic fluid is practically urine so the baby cannot be harmed directly by your urine. Christy, though, sites possible problems; if you are worried you could use it homeopathically, else use a few drops sublingually.