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Title: An exploration of the relationship between termination of a first pregnancy and outcome of subsequent pregnancies
Author: Fitzmaurice, Ann E.
ISNI:       0000 0004 2726 1868
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2012
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The impact of a termination on subsequent pregnancy outcomes has been widely studied. It has been suggested that women who terminate a pregnancy are more likely to have an adverse outcome of a subsequent pregnancy, either miscarriage, or a preterm or low birthweight baby. However, the evidence to date is inconclusive and in some cases contradictory. Hypothesis: It is hypothesised that those who had terminated their first pregnancy are more likely to have an adverse outcome of a subsequent pregnancy, (either miscarriage, preterm delivery (<37 weeks), or low birthweight ((<2500g) as a proxy for gestation). They are also more likely to have shorter gestation at miscarriage, and the gestation at miscarriage is associated with method of termination. Also, women are more likely to show a dose-response in three-pregnancy series, with increasing numbers of consecutive terminations associated with increasingly poorer outcomes. Data and Methodology: Setting and Sample: Aberdeen maternity hospital (AMH) is the level III consultant-led maternity unit for NHS North of Scotland Region. It provides care for pregnant women both with and without complications and for sick neonates. The data were extracted from the Aberdeen Maternity and Neonatal Databank (AMND), with the sample restricted to Aberdeen city women in 1970-1999, and only singleton pregnancy events were included. Outcomes The study group was Termination-Birth (TB) and this group was compared to three comparison pregnancy history groups, Miscarriage-Birth (MB), Birth-Birth (BB) and Birth (B). The outcomes are preterm and low birthweight deliveries and the sub-categories of preterm and low birthweight. In addition, miscarriage on the index event is also considered as an outcome. Methods: The distributions of gestation and birthweight were examined between and within study groups for outcomes of preterm and low birthweight deliveries, and logistic and multinomial regression was used to assess the impact of selected potentially confounding socio-demographic and pregnancy related characteristics on the odds of delivering at different levels of preterm and low birthweight by pregnancy history. The gestation at miscarriage of the index subsequent event is also examined between study groups, as is the method of termination for women whose first pregnancy was terminated. In addition, two and three pregnancy sequences are examined to determine if there was a ‘dose-response’ effect of termination of pregnancy. Results: For women from group TB, the overall difference in average adjusted gestation at delivery is approximately 1 day less for women from group TB compared to women from group MB, and only 2 days from women with only a history of births, these results could be considered clinically insignificant. This thesis has shown that compared with women with a previous birth, and after adjusting for possible confounding factors, births after a previous termination were consistently more likely to result in a preterm delivery. Women who terminated a first pregnancy have an increased likelihood of preterm delivery from a public health perspective, with an overall 40% increase in risk for preterm birth for women from group TB when compared to women from group B (OR 1.35 95%CI 1.15, 1.58). These increased odds of preterm delivery for group TB are very similar to those for women from group MB (OR 1.45, 95%CI 1.18, 1.79). Similarly, after adjustment for potential confounding factors, women from group TB were consistently more likely to deliver a low birthweight baby, when compared to women with from group B, (OR 1.18 95%CI 1.00, 1.38). Women from group MB were also significantly more likely to deliver a low birthweight baby after adjustment for possible confounding factors (OR 1.42 95%CI 1.16, 1.72). Few if any of the explanatory variables are directly modifiable, and the PAF associated with women from group TB is relatively small, when compared to other significant potential risk factors. Women who terminated a first pregnancy were significantly more likely, after adjustment for socio-demographic characteristics to miscarry late (OR 1.74, 95%CI 1.07, 2.84), but there was no difference between medical and surgical terminations. Finally, there was no evidence of a dose response of termination for either preterm or low birthweight deliveries, although there was marked evidence of a dose response of miscarriage. Conclusions The results from a clinical and public health point of view may appear to be contradictory, in that there is an approximate 40% increase in relative risk for preterm delivery, but only an adjusted absolute difference of two days lower gestation at birth for women from group TB. PAF findings indicate only a small overall reduction in the number of preterm deliveries if the exposure to the risk factor of a previous termination was eliminated. Women who undergo a termination should therefore receive full information on factors which might have an influence on the outcome of a subsequent pregnancy, and in addition medical information given to the women should cover details about the termination process, including methods of termination, possible complications, post termination follow up and future contraception.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Abortion ; Labor ; Induced (Obstetrics) ; Pregnancy