The researchers studied 127 young women from three sexual health clinics. All of them had started having periods within the preceding five years or were aged 17 years and under.
The young women were screened for genital infections, including chlamydia, wart virus (human papillomavirus or HPV), and bacterial vaginosis.
Almost two thirds of the young women tested positive for HPV, half of which were the high risk types associated with the development of cervical cancer. Over half of those infected with HPV had at least one other infection.
Around one in four tested positive for chlamydia, which is associated with infertility.
Specific behaviour patterns had specific effects on particular infections.
A recent new partner or use of a condom was associated with a lower risk of chlamydial infection, while the use of emergency contraception doubled the risk. Sex during a period also increased the risk of bacterial vaginosis. Smoking conferred protection against HPV.
But sexual maturity had a significant impact on all three infections.
Young women, whose breasts were more developed, more sexually mature (older gynaecological age), and who had infrequent menstrual cycles (oligomenorrhoea) were significantly less likely to have any of the infections.
After taking account of age, number of sexual partners, and behavioural risk factors, young gynaecological age remained a strong predictor of infection risk.
The authors say that early maturers, who start their periods before the age of 12, have high oestrogen levels and develop physically faster than late developers. This could help cut their infection risk.
They conclude: "We suggest that a sexually active 18 year old with late [periods] may be more susceptible to multiple infections than a sexually active 15 year old with early [periods]."
Sexually Transmitted Infections