Pregnancy outcome in primigravid women above the age of 30 years in Soweto

Abstract

BACKGROUND Delaying the first pregnancy into the thirties is infrequent in low to middle-income South Africans. While primigravidas ≥35 years old are generally considered a high-risk group, it is not known if women aged 30-34 are also at risk for complications and poor pregnancy outcomes. OBJECTIVE To determine the frequency of primigravidity at ≥30 years, and to determine thepregnancy risks and outcomes in primigravid women aged ≥30 years, compared to a reference group of primigravidas aged 20-24 years. METHODS This was a cross-sectional analytic study of primigravid women resident in Soweto, giving birth to babies weighing ≥500 g at the Soweto maternity services (Chris Hani Baragwanath Hospital and five midwife obstetric units).Pregnancies in women aged ≥30 years were sampled as cases, with those aged 20-24 sampled as controls (reference group).The proportions of primigravidas in the case group and the reference group giving birth at the hospital, as opposed to the midwife obstetric units, were determined before starting the cross-sectional analysis. Because there was no significant difference in hospital birth proportions between the groups, only hospital births were sampled for the study, in a 1:1 ratio of cases to controls. Clinical data werecollected prospectively from hospital case files. The key outcome measures were caesarean section, low birth weight and admission of the newborn baby to the neonatal unit. RESULTS Seventy-six primigravidas aged ≥30 years were sampled, with an equal number of controls aged 20-24 years. Antenatal differences included a lower mean gestational age at booking in the cases (17.9 vs. 20.5 weeks; P<0.01), as well as greater maternal weight at booking (86.6 vs. 73.1 kg; P<0.01), and evidence of further progression of HIV disease in terms of mean CD4 cell count (206 vs. 372 cells/mm3; P<0.01). However, the HIV seroprevalence was not significantly higher in cases (24.3% vs. 19.7%; P=0.55). Caesarean delivery rates were high in both groups (55.3% vs. 48.7%; P=0.63). There were no significant differences in any other pregnancy outcomes, although there was a trend to lower mean birth weight in cases (2849 vs. 3050 g; P=0.06). CONCLUSION Primigravidas of age ≥30 years were not found to be at risk for adverse pregnancy outcomes in this small cross-sectional study. The findings of increased maternal weight and further progression of HIV disease in cases were not unexpected, as these are age-related phenomena. Based on the findings here, it will not be appropriate to assign high risk pregnancy status to primigravidas of age ≥30 years.