OS096. Characteristics of hypertensive disorders in twin versus singleton pregnancies

Pre-eclampsia is well characterised in single pregnancies but less well in twin pregnancies, where the risks are higher.

The aim of this study, therefore, was to determine the characteristics of hypertensive disorders of pregnancy (HDP) in twin compared with singleton pregnancies.

We performed an analysis of 4976 prospectively recorded hypertensive pregnancies. These included pre-eclampsia (PE), gestational hypertension (GH) and chronic hypertension (CH). The rates and characteristics of these disorders were compared between singleton and twin pregnancies as was the progression of GH to PE for both groups. Maternal outcomes for severe hypertension (BP⩾170/⩾110mmHg), eclampsia, total antihypertensive medication requirements and maternal death were compared. Neonatal outcomes evaluated included birth weight, small for gestational age (SGA) and perinatal mortality.

After exclusion of higher order pregnancies (triplets (n=2), a quadruplet pregnancy (n=1)), those with known secondary HT, white coat HT, or not fulfilling strict criteria for an accurate diagnosis (n=470) and those without an initial diagnosis recorded, there were 4156 women comprising 3942 singleton and 214 (5%) twin pregnancies.Hypertension (GH or PE) in twin pregnancy was diagnosed earlier than in singleton pregnancy (34±3 v 36±3 weeks, p<0.001). In the singleton pregnancies with de novo hypertension (n=3161), 60% had an initial diagnosis of GH and 40% had PE. In the twin pregnancies with de novo hypertension (n=199), 35% of women were initially diagnosed with GH and 65% with PE (p<0.001, single v twins). At delivery, 46% of the singletons had GH and 54% had PE, compared with twin pregnancies where 23% had GH and 77 % had PE (p<0.001). The progression from GH to PE for twins was greater than that for singleton pregnancies (34% v 15%, p<0.001). There were also781 singleton pregnancies and 15 twin pregnancies with CH. Twin pregnancies complicated by CH were more likely to progress to PE than singletons (54% v 18%, p<0.01). Women carrying twins were older (p<0.01) and they required less medication compared to those carrying singleton pregnancies(0.9±1.2 v 1.3±1.5 medication score, p<0.05). Other maternal outcomes did not differ between the two groups. For neonatal outcomes, the gestation at delivery was earlier for twin than singleton pregnancies (36±2 v38±2 weeks, p<0.001) and SGA (less than 10th percentile) for twins was higher than singleton pregnancies (22% v 12%, p<0.001).No difference in perinatal mortality was noted.

Women carrying twins who develop hypertension during pregnancy are more likely to present earlier, have initial PE rather than GH and to subsequently progress from GH to PE than in singleton pregnancy. Neonatal outcomes are worse in such pregnancies. It is thus reasonable for pregnant women with twins who develop de novo hypertension to be considered very high risk and possibly be managed in hospital.