Final answer:
Latika is most likely in her twelfth week of pregnancy when the external genitals can be differentiated on an ultrasound.
Step-by-step explanation:
Latika is likely to be around the twelfth week of her pregnancy. The critical detail mentioned in the information provided is that the external genitals of the fetus can be clearly differentiated by week 12 using an obstetric ultrasound. Since it is the first time the fetus's biological sex as a boy has shown up on a scan, Latika has most probably crossed this developmental milestone, which indicates she is likely in her second trimester of pregnancy and specifically beyond the 11th week.