Contributing to Safety Evaluations in Studies in Adolescent and Young Adult Pregnant Women and Their Infants: An Observational Study to Assess Pregnancy Outcomes and Events, and Neonatal and Infant Events (Preprint)
Authors: Dos Santos Gael , Graham Sophie , Brabant Yves , Luttropp Karin , Donaldson Robert , Wang Huajun , Lambrelli Dimitra , Tullio Antonella N. 
Published: June 2022

BACKGROUND

Maternal immunization is expected to be beneficial to mothers and their infants as the antibodies induced by vaccination are transferred through the placenta. To facilitate the interpretation of safety data generated during studies in pregnant women and their infants, reliable background rates for pregnancy outcomes, pregnancy-related events of interest (EIs) and infant EIs are critical. Pregnancy-related and infant EIs, such as preterm birth and low birth weight, are usually more common in adolescent compared to adult pregnancies in low-income countries. However, safety data in adolescent and young adult pregnant women and their infants are scarce in high-income countries.

OBJECTIVE

The objectives of the present study were to estimate the incidence proportions of pregnancy outcomes, pregnancy-related EIs and infant EIs in three different cohorts of pregnant adolescent and young adult women (12–24 years of age) and their liveborn infants.

METHODS

This study was an observational, descriptive, cohort study using pre-existing primary care data linked to secondary care and cause of death data. The study included adolescent and young adult pregnancies and their liveborn infants identified in the Clinical Practice Research Datalink GOLD Pregnancy Register from January 1, 2005 to April 1, 2019. Pregnancies were classified into the following cohorts: All Pregnancies (AP), All Pregnancies with a gestational age (GA) ≥24 weeks (AP24+) and Low-Risk pregnancies (i.e., those without high-risk conditions) with a GA ≥24 weeks (LR24+). The infants of these pregnancies and corresponding infant cohorts (AP infants, AP24+ infants and LR24+ infants) were identified in the Mother-Baby Link (MBL). We calculated the incidence proportions of 7 pregnancy outcomes, 15 pregnancy-related EIs and 11 infant EIs.

RESULTS

A total of 516,999 pregnancies were identified during the study period, resulting in 68,918 pregnancies in the AP cohort, 40,938 pregnancies in the AP24+ cohort and 26,212 pregnancies in the LR24+ cohort. The most common pregnancy outcome across all cohorts was live birth. Miscarriage or termination was reported in 1,579.3 per 10,000 pregnancies in the AP cohort. The EI with the highest incidence proportion across all pregnancy cohorts was fetal/perinatal distress or asphyxia (1,212.6–1,964.4 per 10,000 pregnancies). A total of 35,254 (AP infants cohort), 34,904 (AP24+ infants cohort) and 22,290 (LR24+ infants cohort) infants were included in the different infant cohorts. Incidence proportions of infant EIs did not differ between the cohorts. The most common infant EI across all cohorts was macrosomia (birth weight >4,000 g), followed by minor congenital anomalies, low or very low birth weight and major congenital anomalies.

CONCLUSIONS

The results provide useful background information that is expected to facilitate the interpretation of safety data in ongoing or future studies, including clinical trials, conducted in adolescent and young adult pregnant women and their infants in high-income countries.