Failure of development of the callosal commissural fibers connecting the cerebral hemispheres results in complete or partial agenesis of the corpus callosum (ACC). The incidence of ACC ranges 3%~5% to 1:4000 live births. This paper reports a 34-year-old woman married for 5 years with primary infertility due to ovulation dysfunction who received ovulation induction (OI) and intrauterine insemination (IUI) 3 times. She became pregnant after the third OI and IUI procedures. Unfortunately, it was found that the occipital portion of the bilateral lateral ventricles of her fetus were dilated with narrowing of the anterior part, creating the so-called ”teardropshaped” ventricles (colpocephaly) at 24 gestational weeks on a routine antenatal ultrasound check. After this discovery, isolated ACC with no associated anomalies was the impression. The diagnosis was confirmed at another hospital by MRI, and then the patient decided to terminate the pregnancy.