I think you mean this.
To the OP, this may come into play depending on your timeline. You say the child will be born in October, when is the visa interview?
9 FAM 201.2-3 IMMIGRANT TRAVEL WITHOUT A VISA
(CT:VISA-1471; 02-09-2022)
a. An unexpired immigrant visa (IV), reentry permit, or other valid entry document is required of an immigrant under INA 212(a)(7) except as indicated below.
b. Waiver for Certain Children Not Required to Obtain Visas:
(1) Child Born After the Issuance of Parent's Visa: A child born after the issuance of a visa to an accompanying parent who will arrive in the United States with the parent and apply for admission during the period of validity of the visa issued to the parent is not required to obtain an immigrant visa.
(2) Child Born to an LPR: A child born of a Lawful Permanent Resident mother during a temporary visit abroad is not required to obtain an immigrant visa if
(a) seeking admission within 2 years of birth; and
(b) accompanied by either parent, who is applying for readmission upon first return after the birth of the child. The accompanying parent must be found admissible for the accompanying child to be eligible for admission without an immigrant visa.
(3) Requiring Reentry Document of Child’s Parent: The provisions of 9 FAM 201.2-3 paragraph b(1) and b(2) above apply only if the noncitizen parent is in possession of a valid Form I-551, a valid reentry permit, refugee travel document (lawful permanent resident only), an SB-1 visa, or other appropriate documentation consistent with 8 CFR 211.1(a). With respect to 22 CFR 42.1(d), it is irrelevant whether the visa issued to the accompanying parent is an initial visa or a replacement visa.
(4) Evidence of Parent-Child Relationship: Parents must present the child's birth certificate or other evidence of parentage for the child to qualify under the provisions of 9 FAM 201.2-3 paragraph b(1) and (b)(2) above.
https://fam.state.gov/FAM/09FAM/09FAM020102.html