The following is from http://mumbai.usconsulate.gov/transmission_requirements_.html and lists the transmission requirements for U.S. citizenship. Review it carefully to ensure you are eligible to transmit U.S. citizenship to your baby. This primarily applies to the Affidavit of Presence in the U.S., one of the documents you'll have to complete at the consulate.
Reports of Birth: Transmission requirements for U.S. citizenship
Children born abroad to U.S. citizen parents may have a claim to U.S. citizenship. The following is a brief description of the various circumstances under which a child born abroad acquires U.S. citizenship.
Child born in wedlock to two U.S. citizens: A child born outside of the United States or its outlying possessions to two U.S. citizen parents is entitled to citizenship, provided one of the parents had, prior to the birth of the child, been resident in the United States or one of its outlying possessions. (No specific period of time is required to establish residence.)
Child born in wedlock to one U.S. citizen parent and one non-U.S. citizen parent on or after November 14, 1986: A child born outside of the United States to one U.S. citizen parent and one non-U.S. citizen parent may be entitled to citizenship provided the U.S. citizen parent had been physically present in the United States or one of its outlying possessions for five years, at least two years of which were after s/he reached the age of fourteen. This period of physical presence must have taken place prior to the birth of the child. Click here for Affidavit of Physical Presence form.
Child born in wedlock to one U.S. citizen parent and one non-U.S. citizen parent between December 24, 1952, and November 13, 1986: A child born outside of the United States to one U.S. citizen parent and one non-U.S. citizen parent may be entitled to citizenship provided the U.S. citizen parent had, prior to the birth of the child, been physically present in the United States for a period of ten years, at least five years of which were after s/he reached the age of fourteen.
Child born out of wedlock to a U.S. citizen mother: A child born outside of the United States and out of wedlock to a U.S. citizen mother is entitled to U.S. citizenship provided the U.S. citizen mother had been physically present in the United States for a continuous period of at least one year at some time prior to the birth of her child. (NOTE: The U.S. citizen mother must have lived continuously for 1 year IN THE UNITED STATES OR ITS OUTLYING POSSESSIONS. Periods spent overseas with the U.S. government/military or as a government/military dependent, may NOT be computed as physical presence in the U.S.)
Child born out of wedlock to a U.S. citizen father: A child born outside of the United States to a U.S. citizen father who is not married to the non-U.S. citizen mother is entitled to U.S. citizenship provided the U.S. citizen father had been physically present in the United States for the period of time as specified in previous paragraphs for children born in wedlock to one U.S. citizen and one non-U.S. citizen parent, either before or after November 14, 1986; and
* a blood relationship between the applicant and the father is established by clear and convincing evidence; and
* the father signs a sworn statement agreeing to provide financial support for the child until s/he reaches the age of 18 years; and
* the father provides a written statement acknowledging paternity; or
* the child is legitimated under local law; or
* paternity is established by a competent court before the child attains the age of 18 years.
I believe that my child has claim to U.S. citizenship. What next?
If you believe that your child has a claim to U.S. citizenship, it will be necessary for the U.S. citizen parent to appear in person at this office in order to execute an application for a "Consular Report of Birth Abroad" before a consular officer. At that time, a passport application may also be executed.
What if I do not meet the requirements for transmission of citizenship to my child?
It may be possible for your child to apply for expeditious naturalization or an immigrant visa.
I am over the age of 18 and I believe I have a claim to U.S. citizenship. What next?
If your parent(s) had the prerequisite physical presence in the United States required by U.S. citizenship law in effect at that time, you should e-mail us at [email protected], giving as many details of your situation as possible. We will then let you know if there are any grounds for you to pursue your citizenship claim further.
In an email correspondence, the consulate indicated:
For the Affidavit of presence in the U.S. I'm 40, have lived outside the U.S. half my life, and have traveled quite a bit. Do I need to state the precise dates I lived in the U.S., excluding dates I was traveling? Yes.
Or can I provide documentation showing physical presence in the U.S. for some period of time? Yes, we will also want this, to document those precise dates you will already have listed.
If so, what period of time is required (1 year)? Yes, if both you and your wife are proven to be genetic parents of the child – otherwise, 5 years, 2 of which are after the age of 14. Transcripts are great proofs for this sort of thing, so consider having those on-hand for any education you did in the U.S. (yes, even high school).
If so, what evidence is sufficient? Use your judgment, but things like transcripts, W-2 forms, military records, etc – basically anything that proves you were in the U.S. for a given span of time.
To prove physical presence in the U.S., reports indicate that people have used school transcripts, tax returns with W-2s that indicate full-time employment in the U.S., earnings statements issued by the Social Security Administration, military records, leases, utility bills, etc.
If you have questions about your situation, contact the consulate prior to traveling to India. Starting in 2009, the consulate has become stricter in following these rules and verifying actual presence.