The International Planned Parenthood Foundation says the evacuation of Vanuatu's Ambae has seen a spike in the need for sexual and reproductive health services.
The island was evacuated when a volcano erupted in September, and communities are now returning to food and water shortages.
But the foundation's Nerida Williams, who has just been on Ambae with a team of doctors, said the need for sexual and reproductive health was also a concern.
She said rates of STIs and HIV often spiked in times of emergency, and pregnant women and infants were put through traumatic encounters, which can have a detrimental effect.
"Often in emergencies the need for sexual and reproductive health is completely overlooked. The needs go up, but actually the access goes down. So, for example, heavily pregnant women can't often get the help they need, people don't have access to contraception or to clinics.
"You do see a trend in emergencies where transmission rates of STIs can actually go up, and maternal deaths can actually go up."