Pregnancy outcomes in women with primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) during pregnancy may pose considerable risks to mother and fetus. This study examined pregnancy outcomes in women with gestational PHPT in relation to clinical and laboratory parameters.

This study was designed as a retrospective case series.

The study group included 74 women aged 20-40 years who were diagnosed with PHPT after a finding of serum calcium ≥ 10.5 mg/dL on routine screening at a health maintenance organization (2005-2013) and who became pregnant during the time of hypercalcemia (124 pregnancies). Clinical and laboratory data were collected from the files. Pregnancy outcomes were compared with 175 normocalcemic pregnant women (431 pregnancies) tested during the same period.

The cohort represented 0.03% of all women of reproductive age tested for serum calcium during the study period. Abortion occurred in 12 of 124 pregnancies (9.7%), and other complications occurred in 19 (15.3%) with no statistically significant differences from controls. Hypercalcemia was first detected during pregnancy in 14 of 74 women (18.9%) and before pregnancy (mean, 33.4 ± 29 mo) in 60. Serum calcium was measured antenatally in 57 of 124 pregnancies (46%); the mean level was 10.7 ± 0.6 mg/dL (median, 10.6 mg/dL). Measurement of the serum PTH level (with consequent diagnosis of PHPT) was performed during the first studied pregnancy in 17 of 74 women (23%), before pregnancy (mean, 37.8 ± 25.5 mo; median, 34 mo) in 23 (31.1%), and after delivery (mean, 54.7 ± 45.7 mo; median, 35 mo) in 34 (45.9%). Forty-three women (58.1%) underwent parathyroidectomy, six during pregnancy, without maternal or fetal complications. No difference was found in abortion or any pregnancy-related complication between patients who subsequently underwent parathyroidectomy and those who did not. No significant correlation was found between calcium level during pregnancy and pregnancy outcomes.

Serum calcium levels are usually only mildly elevated during pregnancy in women with PHPT. A significant proportion of cases go undiagnosed. Mild hypercalcemia in gestational PHPT is generally not associated with an increased risk of obstetrical complications.