A woman gave birth to twins conceived a week apart after she fell pregnant with a second baby while already expecting. Odalis Martinez, 26, fell pregnant with her first baby on the last day of her menstrual cycle - before she conceived a second five days later.
The mum-of-two was told by the ultrasound doctor babies, Lilo and Imelda, now one, were 'measuring differently' and had been conceived at different times. The phenomenon is called superfetation and is "extremely rare". It happened after she released two eggs instead of one during her cycles - and both were fertilised by different sperm.
