“Oh, no — my baby!”

That was traumatized Jennifer Aniston’s first thought after a horrifying car wreck on January 15 left her weeping and in pain at the side of a busy Hollywood street.

When her Jaguar was broadsided as she was driving to work, the “Friends” star feared the jarring impact might cause a miscarriage, shattering her dreams of having a baby with husband Brad Pitt. Witnesses say she left her damaged car, sat down at the curb, buried her head in her hands — and sobbed.

“Jennifer wants to have a baby so badly,” a source told The ENQUIRER. “It was the most terrifying moment of her life!”

Fortunately for 32-year-old Jennifer, her injuries weren’t serious. But that didn’t make her ordeal any less traumatic.

“The accident took place about 10:30 on Tuesday morning,” a witness told The ENQUIRER. “Jennifer was driving along Fuller Avenue when a Volkswagen Jetta pulled out of an apartment building driveway and plowed into Jennifer’s silver XJ8 Jaguar, propelling Jen’s car to the other side of the road!”

There was no oncoming traffic on the narrow street or the accident might have been tragic — but it was bad enough to terrify Jennifer.

“She was so badly shaken that she sat dazed in the driver’s seat for a few moments before attempting to get out of her car,” said the witness, “and when she finally did, she was trembling. At one point, Jennifer buried her head in her hands and started to sob!

“When paramedics arrived, Jennifer told them her back and side ached from the impact. They wanted to rush her to the nearest hospital, but she decided to get medical help on her own.”

The star called her personal assistant, who arrived within minutes to take her to her doctor.

“But even as she left the scene, Jen looked very distraught,” the witness said. “It was obvious she was living a nightmare.”

Sources say Jennifer’s distress was caused by the fact that Jennifer thought she might be pregnant — and that the wreck would cause her to miscarry.

Jennifer won the People’s Choice Award for best television actress two days before her accident.

“Jennifer and Brad are trying to start their family and she had told the producers of ‘Friends’ their plans,” said an insider. “Of course, they happily wrote the story line into the show. So if she were pregnant, the possibility of losing the baby and having to play out the pregnancy story line on ‘Friends’ really threw her.”

Jennifer is so committed to getting pregnant that she’s even quit smoking. And babies have been so much on her mind that for a couple of weeks prior to the accident Jennifer hoped she was pregnant — and was waiting a little longer before doing a pregnancy test or checking with her doctor, the source told The ENQUIRER.

“Jen said she’s enjoying the thought that at any moment she could be expecting,” the source said. “That’s why her first thoughts on the morning she was hit were of the baby she hoped she was carrying. She felt true maternal instincts rush over her — concern for the life inside her.”

After Jennifer saw a doctor after the crash, the doctor told her she wasn’t pregnant, but was in perfect health and can eventually conceive.

“Jennifer was disappointed because she really wants to be a mom,” the source said. “But on the other hand, she’s glad she wasn’t pregnant at the time of the crash — it would be a nightmare if she had lost a child.”

The wreck has turned out to be a mixed blessing for Jennifer and Brad, sources say, because it renewed their resolve to realize their cherished dream of having a child. And loving husband Brad has been deeply affected by his wife’s brush with disaster.

“He was so shaken up by the crash that he’s refused to allow Jennifer to drive,” another source told The ENQUIRER. “He now wants a chauffeur with her at all times.”