Effect of Advanced Maternal Age on Pregnancy Outcomes: A Case Control Study at Mpilo Tertiary Teaching Hospital, Bulawayo, Zimbabwe, 2004- 2005

Abstract

The average age of giving birth by women in developing countries is beginning to catch up to those of developed countries, the reasons for the increase are however different in some respects from those of developed countries – within western societies its mostly choice, but developing world its usually out of desperation or someone’s voice, that is choice vs voice. In the developed world the reasons for conceiving well after age of 35 years are usually pursuing demanding careers, furthering education, divorces, amongst others. Unfortunately, these pregnancies by older women are characterised by multiple problems. The current average for advanced maternal age (AMA) Zimbabwe is not well documented. Interestingly, the average varies between rural and urban areas. According to the ZIMSTATS and UNICEF (2019), the Zimbabwe Multiple Cluster Index Survey of 2019 showed that of those surveyed, women less than 20 years had 420 births, those 20-34 years had 1601 births, whilst women of age group 35-49 years had 351 deliveries – this translates to 14.8% contribution from AMA. The study is a prospective comparative observational case control study conducted at the department of Obstetrics and Gynaecology, Mpilo’s Maternity Hospital in Bulawayo, Zimbabwe. The study population consists of pregnant women at least 35 years of age including primigravida (delayed childbearing) and multiparous women (continued childbearing). Advanced maternal age is defined as age of mother of 35 years or more at the time of delivery. The study group comprised of women of advanced maternal age who deliver during the study period. The control group are women aged 20-34 years who delivered on the same day as women included in the study group. In this population mode of delivery, low birth weight and low fifth minute Apgar score were found to be significantly associated with maternal age. Babies born from advanced age mothers had 4.2 times higher odds to be born with low birth weight (AOR 4.2, 95% CI (1.76–4.9), p < 0.001) as compared to mothers aged less than 35 years after adjusting for other variables. Similarly, babies born from advanced age mothers had 6.7 times higher odds to have low fifth minute Apgar score (AOR 6.7, 95% CI (1.28–12.3), p =0.03) than babies born from mothers aged less than 35 years old holding other variables constant. Furthermore, advanced age mothers were 3.9 times higher odds to undergo caesarean section than their controls (AOR 3.9, (95% CI 1.52–3.78), p = 0.012). There was no statistically significant association between maternal haemorrhage and maternal age. The findings in this paper suggests that multiple factors predict AMA births and also many adverse outcomes of such pregnancies. Better characterization of the circumstances that lead to advanced maternal age in Zimbabwe, including exploration of AMA pregnancies within and beyond control is necessary to develop policies and interventions that meet women's needs. For those that get pregnant after 34 years of age a more focused and integrated management pathway should be advocated and implemented.