CF Patients With Poorer Lung Function at Greater Risk of Premature or Smaller Baby, Study Shows

Pregnancy is generally safe for both women with cystic fibrosis (CF) and their child, but those with poorer lung function are at greater risk of having a premature or smaller baby, according to a U.K. population-based study.

The study, “The outcome of pregnancy in women with cystic fibrosis: a UK population based descriptive study,” was published in the International Journal of Obstetrics and Gynaecology.

Improvements in CF care standards have allowed more women with the disease to become pregnant. However, their chronic disease may pose a serious risk to their own health and to that of their baby.

That is why determining the risk of pregnancy-associated complications in women with CF is key to helping them make informed decisions regarding pregnancy and family planning.

Previous studies suggest that pre-pregnancy lung function is the stronger predictor of pregnancy outcomes for both mother and baby. Severely impaired lung function — less than 50% of predicted FEV1 (the amount of air a person can exhale in one second) — is associated with an increased risk of premature delivery (prior to 37 weeks of gestation), cesarean section, and low birth weight.

While FEV1 of less than 50% has been advised as a contraindication to pregnancy in these women, successful pregnancies in those with 20–30% of predicted FEV1 have been reported.

“Further study is necessary to clarify current outcomes for pregnancy in women with CF across wide ranges of lung function and under contemporary CF care,” the researchers wrote.

Researchers at the Oxford University Hospitals NHS Foundation Trust now have analyzed pregnancy outcomes in all women with CF seen at obstetric units in the U.K. from March 2015 to February 2017.

The population study was based on the UK Obstetric Surveillance System, which collects data on rare disorders in pregnancy through a prospective monthly case-collection scheme.

The team analyzed the occurrence of pregnancy in women with CF, health problems and deaths in both the mother and the child, as well as the time of gestation at delivery.

Data showed that 71 women with CF were pregnant during the two-year period analyzed, resulting in an estimated incidence of 4.4 pregnancies with CF in 100,000 U.K. maternities.

There were no maternal deaths and a total of 69 babies were delivered, including three sets of twins. Twenty infants (29%) were admitted to a neonatal intensive care unit.

About one third (38%) of the deliveries were pre-term (prior to 37 weeks), with obstetric reasons behind two thirds of those induced.

“Women may be reassured that — although there is an increased chance of pre-term birth — in the majority of our cases it was not because of worsening respiratory disease,” the researchers wrote.

In total, 25 babies (36%) were delivered by caesarean section, which “is only slightly higher than the 30% caesarean section rate in the general population,” the team noted. Caesarian sections were more frequent among preterm (55%) than normal term (21%) deliveries.

Of the 56 women with available FEV1 values before pregnancy, 17 had moderately reduced lung function (FEV1 of less than 60% predicted). Fourteen of them (82%) completed the pregnancy, two (12%) terminated it due to maternal health reasons, and one (6%) miscarried in the first trimester.

Most (64%) of those completing the pregnancy delivered a baby after 37 weeks of gestation. In these women with poorer lung function, the babies’ mean gestation at delivery was 36 weeks, which was not different from the 36.2 weeks mean for all women.

One infant died following spontaneous preterm birth at 29 weeks from a mother with 47% of predicted FEV1.

Two women with FEV1 more than 60% also terminated their pregnancies: one following a CF diagnosis in the fetus, and one for personal reasons.

“Our data suggest that pregnancy is possible and that fetal outcomes are good in most women booking for their obstetric care with a diagnosis of CF, even in those with a starting FEV1 [less than] 60%,” the researchers wrote.

The team noted, however, that the actual number of pregnancies in women with CF during the two-year period may have been higher, since it was based on prenatal care appointments (usually started at the end of the first trimester), likely missing early miscarriages and terminations.