WASHINGTON – New Zealand mothers who attended childbirth classes during pregnancy were 58% less likely to delay their infants’ first-year immunizations than were those who didn’t take the classes, Dr. Cameron Grant said at the annual meeting of the Pediatric Academic Societies.
The findings of his large prospective cohort study show that early engagement with a maternity clinician is important not only for mothers’ health, but for babies’ as well, said Dr. Grant of the University of Auckland (New Zealand).
The data were drawn from "Growing Up in New Zealand," a large, ongoing study of children’s health from birth to age 21 years; Dr. Grant is also the associate director of this project.
The birth cohort is culturally, racially, and economically diverse, and includes about one-third of the New Zealand births that occurred from April 2009 to March 2010. Mothers were contacted during their pregnancy and had face-to-face interviews when the infant was 6 weeks and 9 months old. There were also phone interviews at 16, 24, and 31 months. Four-year interviews started this year.
The immunization study included 6,822 mothers and their 6,846 children. It examined the links between infant immunization and the maternity care provided in the country. Typically, women attend childbirth preparation classes and their prenatal care is provided by a maternity clinician, usually a midwife. After birth, a community nurse provides well-child visits, but the mother and child return to their family doctor for immunizations. The New Zealand infant immunization series consists of the DTaP, hepatitis B/Hib, and conjugate pneumococcal vaccine, which are given at 6 weeks, 3 months, and 5 months. Delayed immunization was considered as not getting the 6-week immunizations by 8 weeks, or not getting the 3- or 5-month immunizations within 30 days of the due dates.
Mothers in the study are a diverse group, with 52% being white, 16% Maori, 14% Pacific Islanders, 14% Asian, and 4% other. Nearly a third was in the country’s lowest socioeconomic group. The pregnancy was the first for 42%.
Immunizations were delayed for 1,353 (20%) of the infants. Immunizations were on time for 88% of the women who attended childbirth classes, compared with 74% of those who did not, translating to a 62% risk reduction (odds ratio, 0.38).
A univariate analysis found several other significant predictors. Having a midwife significantly reduced the risk of delayed immunizations (OR, 0.43), as did going to any of the three infant well child visits (OR, 0.45).
However, after researchers adjusted for maternal ethnicity, age, and household income, only class attendance and well-child visits with a physician remained significantly associated with immunizations. Those who went to the class were 58% less likely to delay immunizations than were those who didn’t go to the class (OR, 0.42), and 24% less likely to delay than were those who had not gone to the class, but said they intended to (OR, 0.76). Women who visited their doctor for all three well-child visits were 55% less likely to delay immunizations (OR, 0.45).
During the discussion, Dr. Simon Hambidge, a professor at the Colorado School of Public Health, Denver, asked if the association could be a proxy for overall engagement with the health care system or an indicator of some more fundamental force influencing the decision to vaccinate.
"I really do think the health care system has a big role on whether immunization occurs or not," Dr. Grant said. "Moms from the poorest households had the highest intention to immunize their children, but the lowest actual immunization timeliness. I think that points to a number of barriers in health care that we should work hard to overcome, rather than just telling women it’s all up to them to get themselves organized and make sure it happens. We just have to make this more available."
The study is sponsored by a number of New Zealand and Pacific Island government agencies. Dr. Grant had no financial disclosures.