Risk factors and birth outcomes of anaemia in early pregnancy in a nulliparous cohort

Abstract

Background: Anaemia in pregnancy is a major public health and economic problem worldwide, that contributes to both maternal and fetal morbidity and mortality.

Objective: The aim of the study was to calculate the prevalence of anaemia in early pregnancy in a cohort of 'low risk' women participating in a large international multicentre prospective study (n = 5 609), to identify the modifiable risk factors for anaemia in pregnancy in this cohort, and to compare the birth outcomes between pregnancies with and without anaemia in early gestation.

Methods: The study is an analysis of data that were collected prospectively during the Screening for Pregnancy Endpoints study. Anaemia was defined according to the World Health Organization's definition of anaemia in pregnancy (haemoglobin < 11g/dL). Binary logistic regression with adjustment for potential confounders (country, maternal age, having a marital partner, ethnic origin, years of schooling, and having paid work) was the main method of analysis.

Results: The hallmark findings were the low prevalence of anaemia (2.2%), that having no marital partner was an independent risk factor for having anaemia (OR 1.34, 95% CI 1.01-1.78), and that there was no statistically significant effect of anaemia on adverse pregnancy outcomes (small for gestational age, pre-tem birth, mode of delivery, low birth weight, APGAR score < 7 at one and five minutes). Adverse pregnancy outcomes were however more common in those with anaemia than in those without.

Conclusion: In this low risk healthy pregnant population we found a low anaemia rate. The absence of a marital partner was a non-modifiable factor, albeit one which may reflect a variety of confounding factors, that should be considered for addition to anaemia's conceptual framework of determinants. Although not statistically significant, clinically, a trend towards a higher risk of adverse pregnancy outcomes was observed in women that were anaemic in early pregnancy.

Fig 1. Conceptual model of the determinants of anaemia, reproduced with permission from Balarajan et al. [18].

Fig 2. Participant flow chart, adapted from McCarthy et al. [28].

Fig 3. Kaplan-Meier plot estimates of anaemia status and gestational age at delivery.

(Note the ‘curious’ behaviour of women with moderate anaemia who have no pre-term birth and are on average—median and mean—delivering later than women with mild anaemia and even those with no anaemia—median.).