Blood tests were required for marriage licenses primarily to screen for syphilis, a sexually transmitted infection that could be passed between spouses and from mother to child during pregnancy. Starting in the 1930s, nearly every U.S. state made these tests mandatory before issuing a marriage license. The laws stayed on the books for decades, with the last state, Mississippi, finally dropping its requirement in 2012.
Syphilis Was the Original Target
The idea of requiring a health screening before marriage dates back to 1913, when several states began passing laws that required applicants to submit a personal statement of good health. But these early requirements had no teeth. Couples simply signed an affidavit and moved on.
Connecticut changed the game in 1935 by requiring an actual blood test for syphilis along with a physical examination of both applicants. That law became the template for similar legislation across the country. By the late 1930s, states were widely adopting the Wassermann Test, an early blood test for syphilis, and a marriage license would only be issued if both people tested negative.
The principal goal was straightforward: prevent syphilis from being transmitted to a spouse or to future children. Congenital syphilis, passed from a pregnant woman to her baby, could cause stillbirth, premature death, and lifelong health problems. Lawmakers saw the marriage license as a natural checkpoint, a moment when the state could intervene before a family was started.
The Eugenics and Social Reform Connection
These laws didn’t emerge in a vacuum. They were deeply tied to early 20th-century reform movements that aimed to stamp out prostitution, eradicate sexually transmitted infections, and reshape American sexual behavior. Advocates framed mandatory testing as protecting “innocent women from lives of misery” and securing a child’s right to be “well born.” The language of the era blended genuine public health concerns with eugenic ideology, the belief that society should actively control who reproduced and under what conditions. Medical fitness for marriage was seen as both a civic duty and a moral imperative.
Testing Expanded Beyond Syphilis
Over time, some states added other screenings to the marriage license process. Connecticut, for example, added rubella (German measles) testing in 1978 for women under 50 who could become pregnant. Rubella during pregnancy can cause serious birth defects including deafness, heart problems, and intellectual disability. If a woman tested negative for immunity, she had to be informed of the risks to a future pregnancy, though the state couldn’t deny the license based on the result.
New York took a different approach and added screening for sickle cell anemia, a genetic blood disorder. Under that law, applicants who were not white, Indian, or Asian were tested for sickle cell trait. A positive result couldn’t be used to deny a marriage license, and people could opt out on religious grounds. Still, the racial targeting of the law reflected the same uncomfortable overlap between public health goals and discriminatory assumptions that had shaped the earlier syphilis requirements.
Why Penicillin Changed Everything
The discovery of penicillin during World War II fundamentally undercut the case for mandatory premarital testing. By 1947, penicillin was the standard treatment for syphilis and proved highly effective. In the United Kingdom, the antibiotic reduced syphilis cases by 90% within a decade. Syphilis went from a feared, difficult-to-treat infection to a curable one, which made the urgency of catching it at the marriage license office far less compelling.
Vaccines had a similar effect on rubella screening. Once widespread vaccination made congenital rubella rare, requiring immunity testing before marriage added cost without meaningful benefit.
The Math Stopped Making Sense
By the 1970s and 1980s, the numbers told a clear story: mandatory premarital blood tests were catching almost no one. A 1978 study in New York City found that out of 116,000 premarital tests performed at a total cost of $2.3 million, only 39 cases of syphilis were detected. That worked out to roughly $60,000 per confirmed case.
The economics only got worse over time. By 1992, California’s premarital screening program cost more than $20 million annually while producing just $600,000 in direct health benefit. Finding a single case of syphilis cost the state $413,122. Meanwhile, people were actively avoiding the requirement. In San Diego, a large percentage of couples applied for “confidential” marriage licenses specifically to skip the blood test.
A California legislative analysis summed it up bluntly: “the evidence is clear that the premarital blood test provisions are no longer medically justified, or cost effective.” States began repealing their laws in the 1970s, and the trend continued steadily for four decades until Mississippi became the final holdout to drop the requirement in 2012.
Where Syphilis Screening Moved
The end of premarital blood testing didn’t mean the end of syphilis screening. It just moved to a more effective point in the healthcare system: prenatal care. Today, virtually every state requires that pregnant women be tested for syphilis during pregnancy, and many require a second test later in pregnancy or at delivery. Hospitals are required to determine a mother’s syphilis status before discharging a newborn, and infected infants must be evaluated and treated.
This shift makes more medical sense. Rather than testing everyone who applies for a marriage license (many of whom won’t become pregnant for years, if ever), prenatal screening catches infections at the moment they pose an actual risk to a child. It also reaches women regardless of marital status, closing a gap that the marriage-based system never addressed.