Congress left for vacation last week without crossing off a critical item on its agenda: resolving a stalemate over how to fund efforts to combat the Zika virus. A compromise proposal stalled over Republican stipulations that none of the Zika-prevention funding go to family planning organizations like Planned Parenthood. Given that the biggest threat posed by Zika is to pregnant women and their newborn children, Republicans made a serious mistake by shortchanging a major provider of care to women in their childbearing years.

Four out of five of those affected by Zika suffer no symptoms at all. But if pregnant women become infected, especially during the first trimester, the consequences can include miscarriages, stillbirth and microcephaly, a grave birth defect marked by abnormally small heads and lack of brain development. And although developing fetuses are at greatest risk, children and adults can become seriously ill as well. The first Zika death in the continental U.S., which occurred late last month, was that of an elderly man.

According to the U.S. Centers for Disease Control and Prevention, 1,306 people in the U.S. have already been infected with the virus – including 346 pregnant women – and there have been nine births involving Zika-related defects.

Preventing unintended pregnancies will prevent these tragic outcomes. That’s why, in order to fight Zika, which is transmitted both by infected mosquitoes and sexual contact, the CDC and the World Health Organization are urging women to delay getting pregnant.

And that’s why the $1.9 billion Zika emergency spending proposal presented by President Obama in February included funds to promote increased access to contraception.

But Republicans came back with a $1.1 billion compromise that would block any Zika-related funds from going to Planned Parenthood (or similar groups) for birth control. Democrats rejected the plan, resulting in a stalemate that will likely outlast the seven-week congressional recess.

The bill that stalled in Congress targeted the groups that serve the women who are most likely to get pregnant unintentionally: the young and the poor. Many of those women live in states like Florida, Mississippi, Texas and Louisiana, where access to birth control has been decimated by budget cuts, politically motivated attacks on Planned Parenthood and the rejection of Medicaid expansion. This is also the region of the U.S. that’s expected to be hardest hit by Zika.

Some in Congress argue that women have an option to Planned Parenthood: local clinics that provide family planning services with federal Title X funds. But the House Appropriations Committee recently approved a Republican proposal to defund Title X programs (though Title X is barred by law from covering abortion services).

Thousands of women and children could be devastated by the lack of resources to fight Zika – but that’s what happens when politicians fail to put their constituents’ best interests first, and allow partisanship to take precedence over public health.