Perinatal outcomes associated with the positional relationship between the placenta and the adenomyosis lesion

Although various perinatal complications have been reported to be increased in the pregnant patients with adenomyosis, it is not clear what type of patients with adenomyosis is more likely to cause obstetric complications. In this study, we focused on the positional relationship between the placenta and adenomyosis lesion in evaluating perinatal prognosis of pregnant patients with adenomyosis.

This retrospective cohort study was carried out between 1 January 2005 and 31 December 2019 in a single institution. Adenomyosis was diagnosed by magnetic resonance imaging (MRI) and/or transvaginal ultrasonography (TVUS). To evaluate the influence of adenomyosis on perinatal outcomes, we classified the positional relationship between the placenta and the adenomyosis lesion into two groups and examined the perinatal prognosis of the patients with adenomyosis by analyzing their clinical records. Group I (n = 9) was defined when the placenta was not overlaid on adenomyosis lesion. Group II (n = 11) was defined when a part of the placenta was overlaid on adenomyosis lesion.

Twenty pregnant patients with adenomyosis were analyzed. There were no differences in clinical backgrounds between group I and group II. There was a significant increase in the obstetric morbidity in group II than that of Group I(group I: 6.3%, 4/63 vs group II: 18.6%, 26/77; P < 0.001). In group II, fetal growth restriction (FGR) was more frequent (0%, 0/9 vs 45.5%, 5/11; P = 0.042) and the birth weight was significantly lower than that in group I (2951.1 g ± 326.5 g vs 2318.9 ± 656.1 g; P = 0.037). There was a trend of lighter weight of the placenta in group II (550.6 ± 66.5 g vs 437.5 ± 117.8 g; P = 0.063) and the volume of bleeding during delivery was a higher trend in group II than that in group I (845.1 ± 367.1 g vs 1356 ± 604.8 g; P = 0.083). Group II was furtherly subdivided into group IIa (less than half the major axis of the placenta overlaid on adenomyosis lesion) and group IIb (more than half the major axis of placenta overlaid on adenomyosis lesion). The obstetric morbidity tended to be higher in group IIb than in group IIa (group IIa: 22.9%, 8/35 vs group IIb: 42.9%, 18/42); P = 0.09). In group IIb, the frequency of FGR was significantly higher (group IIa: 0%, 0/5 vs IIb: 83.3%, 5/6; P = 0.020) and the birth weight was significantly lower than those in group IIa (2656.8 ± 231.9 g vs 2037 ± 780.1 g; P = 0.040). All cases of FGR, hypertensive disorder of pregnancy (HDP), and oligohydramnios were observed in group IIb.

Placental localization near adenomyosis may increase the risk of perinatal complications.