Palestinian medics and witnesses said the targets were a group of resistance fghters and a plastics factory, both east of Gaza City. All of the wounded were at the factory, they added.
Gaza medical official Adham Abu Selmiya told AFP that the expectant mother was one of two women hurt in the attacks, but described the injuries of all four as "moderate".
An Israeli military spokeswoman told AFP that aircraft hit "two terror tunnels", a phrase the army uses to refer to tunnels being prepared by Gaza resistance fighters to launch cross-border raids.
On Tuesday, as Palestinian factions met to discuss tensions with Israel along the Gaza border, Israeli army fire killed a man in the north of the strip.
"A Palestinian was killed by an Israeli tank shell near Erez," Gaza medical official Abu Selmiya said at the time, identifying him as 21-year-old Mohammed Ziyad Shalha.
Earlier, witnesses reported seeing Israeli troops firing at two men in the same area who were said to be collecting gravel, in what was understood to be the same incident.
The Israeli army confirmed firing at someone near the border fence, but a spokeswoman mentioned only one person, who she said was armed and had been hit.
"The Israeli Occupation Forces (IOF) identified an armed man near the security fence in the northern Gaza Strip and fired towards him," she said. "They identified a hit."
The area along the Gaza border has been declared a no-go zone by the Israeli military for fear of attacks, and troops often fire on Palestinians who venture into it.
But residents often risk injury or death to enter the zone in search of gravel, which they can sell to builders.
Later, two mortar rounds were fired from Gaza into southern Israel, but exploded in a field without causing casualties or damage, Israeli media said.
An Israeli army spokeswoman said late Tuesday that a projectile or projectiles had fallen inside Israel, but she had no further details.
Such cross-border fire routinely draws retaliatory air strikes from Israel. Gaza's Hamas rulers met Tuesday with representatives of all Palestinian factions to discuss "the situation on the ground", officials told AFP.
The meeting was called a day after a Gazan engineer, who was allegedly kidnapped by Israeli agents from Ukraine in February, was indicted for building rockets for Hamas militants.
Several days earlier, three Hamas militants were killed in an Israeli air strike in what the army called a pre-emptive attack against a cell planning to kidnap Israelis from Egypt's Sinai.
The move prompted vows of revenge, despite a fragile ceasefire on rocket attacks that has been declared by militant groups.