Let's take a look at what the scientific literature supports.
oxfordjournals.org said...
4.2. Outcome of pregnancy and adverse outcome of offspring
ECCO Statement 4B
Cesarean delivery is more frequent in women with IBD; and there is an increased risk of low birthweight and pre-term birth [EL2]. Disease activity at conception or during the pregnancy is associated with preterm birth and low birthweight [EL 3]
ECCO Statement 4C
Adverse fetal outcomes such as low APGAR scores, seizures or admission to an intensive care unit and death, are not increased in babies born at term [EL2]. The risk of congenital abnormalities in offspring from women with inflammatory bowel disease does not seem to be increased [EL2]
Women with IBD have an increased overall risk for adverse pregnancy outcomes. The most consistently described are preterm delivery (before 37 weeks of gestation), low birthweight (LBW) (<2500g) and small for gestational age (SGA) birth.73,84–90
Concerning delivery mode, most studies have shown significantly increased frequency of cesarean section, both elective and performed as an emergency intervention.44,86,89–91 The risk of adverse pregnancy outcome seems to be similarly increased in UC and CD.85,89,90,92,93
Very few studies have evaluated whether there is an effect of IBD on first-trimester outcome of pregnancy (i.e. increased chance of miscarriage or an ectopic pregnancy) and whether there is an effect on the rate of complications of pregnancy (placental abruption, chorioamnionitis, preeclampsia/eclampsia, placenta previa, premature and prolonged rupture of membranes). However, a few studies report there is an increased rate of miscarriage, both spontaneous and induced. Additional data on the frequency of complications of pregnancy and labour are very inconsistent, precluding a meaningful conclusion.44,89–91,93
Disease activity at conception and during pregnancy seems to be an important risk factor for adverse pregnancy outcomes. Several recent studies have examined the impact of disease activity on pregnancy outcomes using proxy measures such as IBD-related surgery and hospitalization before and during pregnancy, change of IBD medication, and low weight gain during pregnancy.85–87,89,90,93–95 The majority have revealed that IBD mothers with active disease at conception and during pregnancy have a higher risk of preterm birth, low birthweight and small for gestational age birth compared with IBD mothers with disease in remission. Other predictors of adverse pregnancy outcomes in IBD, besides disease activity, include familial history of IBD, disease localization and IBD surgery.84,86,88
Source:
The Second European Evidenced-Based Consensus on Reproduction and Pregnancy in Inflammatory Bowel Disease
ecco-jcc.oxfordjournals.org/content/eccojc/9/2/107.full.pdf