Six flechette shells were fired towards the village of Khuzaa, east of Khan Younis, on 17 July, the Palestinian Centre for Human Rights said on Sunday.
Nahla Khalil Najjar, 37, suffered injuries to her chest, it said. PCHR provided a picture of flechettes taken by a fieldworker last week.
The Israeli military did not deny using the shells in the conflict.
B'Tselem, an Israeli human rights organization, describes a flechette shell as "an anti-personnel weapon that is generally fired from a tank. The shell explodes in the air and releases thousands of metal darts 37.5mm in length, which disperse in a conical arch 300 meters long and about 90 meters wide".
The Israeli military has deployed flechette shells in Gaza and Lebanon before. B'Tselem has documented the deaths of nine Palestinians in Gaza from flechettes in 2001 and 2002. Flechettes have also killed and wounded dozens of civilians, including women and children, in conflicts between the Israeli regime and Hezbollah in Lebanon.
The Israeli military deployed artillery shells containing white phosphorous in densely populated areas of Gaza during Operation Cast Lead in 2008 and 2009, causing scores of deaths and extensive burns. It initially issued a categorical denial of reports of the use of white phosphorous, but later admitted it, saying the weapon was only used to create smokescreens.
Human Rights Watch said its use of the munitions in Operation Cast Lead was indiscriminate and evidence of war crimes.
NTJ/MB